Jim (Login 69fstback) Member from IP address 18.104.22.168
I have a 79 mustang and I really want to build a 8.2 deck boss 302 or 331....
I know I can do the 302 with stock crank, 289 length rods, and a boss piston. Or 5.4 rod and 1.3 piston
331 would be 3.25 crank, 5.325 rods, and a 1.250 compression Cleveland piston.
I want this for mainly a street car... Car has 4.30 gears already...Built Aod so overdrive is nice with the 4.30s
Looking to have the same caratistics as a old boss 302...high revving etc
Hoping to get 3200lbs down the 1/4 in low 12s high 11s
Be able to jump in and head down the road... Two pumps of the carb and I'm off...
Pump gas/reliable 93
Things I have already... Which lead me to this build...
Clevor modded 351 4v cc heads
Mexican 302 block bored 30 over fresh
Buddy of mine has a boss 302 intake I can borrow until I find a track boss or another intake
2 sets of forged Cleveland pistons (gotta measure compression height)
Basically I need help making a good combo with the smaller cubes... Should I go high revving 302? 7500rpm...since torque shouldn't be to bad with 4.30 gears...
I think I read go small duration/high lift to get a boss 302 to run? Like 225/230@50 with like 580/595 lift on a 111 intake center line? Trying to get 12-14 vacuum at idle...
Thanks! How did you guys get your old bosses up and moving?!?
Anytime you put 302 cubes with a 235-240cc head, you're going to have to spin the pee out of it to get anywhere. Yes, the 4.30 gear will help and yes the light weight will help, but keep in mind that a 7500 rpm engine is not a street engine and will absolutely be a dog on the bottom end.
If you do plan to turn that many rpms, you will need duration and a ton of it. No vacuum.
I do Boss 302's for vintage Mustang stuff and the engines have no butt to them.
I would throw as much stroke as you can to it, skip the 331 and go with a 347, and stay away from the 7500 rpm goals. Lower duration and ADVANCED cam timing, not 111-112 ICL's. If you can, I would put port tongues in the heads and cut the CSA way down.
I've driven the factory cars and they ran just fine, even with the stock 3.50:1 gearing. I think stuffing one in your '79 is a great idea; 4.30s are the right gear for a 26" tire, according to Ford.
You don't have to ask "should I build a high rpm motor"? Because the moment you decide to bolt the 4V heads on the 302 you've already set that in motion. Its unavoidable, it shall be a high rpm motor. So don't fight it, and don't try to make it somethng it isn't.
Basically the Boss 302 does everything 800 rpm higher than a 351C 4V. But the same Cleveland principles apply. Everything is 180 degrees backwards from motors with small ports and small valves. The Cleveland heads build the high rpm power, and the cam and intake manifold build the low rpm power. So spec a cam with relatively short intake duration and limited overlap, and use a dual plane intake manifold with a full height (un-cut) plenum divider. Carb & ignition calibration are also critical to running smoothly on the bottom end. Your 4V heads have either 63cc chambers or 66cc chambers, whereas the Boss 302 heads had 58cc chambers, so you'll have to make up that difference in volume somehow.
I think you'll like the motor, my advice is go for it.
...to have an engine that makes peak hp at 7500 and has low end manners plus vacuum to boot.
Modern engines can do it with multivalve heads, variable valve timing, EFI, etc. However, it's not like that with big cammed carbureted engines, especially small ones.
Where would you need to be to peak at 7500? Probably with .050" durations in the 240's. That may not sound big, but for a 302, it's huge.
Again, you'll need to figure out which side of the fence you want to be on. The streetable side with plenty of vacuum and some low end power (relatively speaking, Boss 302's don't have low end power), or a 7500 screamer with no niceties down low. I don't think you'll be happy with a 7500 rpm peak on the street, even with a 4.30 gear.
If it were me, I'd not worry about the vacuum and the "driving" part of the engine. I'd cam it to turn some revs so that it will be efficient and make some horsepower. A solid cam with about 240-242 duration @ .050", a 108LSA on a 104ICL, and about .600" lift.
In stock form with the Boss 302 cam (about 228 deg @ .050"), it should make about 375hp at 6600-6700. You could probably get closer to 400 with a little larger cam and a higher peak, but prepared for less and less torque. A stock 5.0 Mustang had more torque than these Boss 302's did.
My old 2003 Mach was kind of like a boss 302 I believe... 4.6...
Made 320 torque at 4500... Peak hp was around 5900-6100... I shifted at 6600-6700...
It had 4.10s... Ran 12.70... I loved the feel of that car... Mellow then wham... Pulled for forever it felt like...
I think that's about what I'm shooting for... Not making peak hp at 7500... More like shifting around 7200-7400...
Peak around 6600-6700
Hi, a former EMC winners have just built a 347 Boss for a friend. Stock 302Boss block, heads,intake.
This is the answer he got in the mail.
I ran the Boss engine on the dyno for several hours today- Everything seems fine, I worked with carburetor jetting quite a bit, and the engine picked up a little--- The best horsepower was jusy under 500 ( like 498 ) and the best torque was right at 445 pounds. The HP was still climbing at 66-6700, but that was as high as I revved it up. I will explain more details later when we talk on the phone===
uses the 1.73 rocker ratio to get the lift, duration. If you buy a NOS Boss 302 camshaft, it is stamped identical to the 289HP solid lifter cam. I have one here in the box. When you use 1.6 rocker arms, it is a 289 cam. I know this will start an argument, but unless Ford screwed up somewhere along the way, I have two of those cams and they are the same. Joe-JDC.
Engine sims are good for comparisons between components....
August 8 2012, 11:53 AM
I use EA Pro for approximations and it's usually 6-7% high compared to the actual dyno. However, it will let you see the difference between two components...such as two cams, an increase in compression, an increase in stroke, etc.
I will say that there's no way whatsoever a 302 will make 379 lb-ft of torque, much less at just 4500 rpm and still make peak hp at 6500...
For cam specs, I use past engine build and dyno experience based on all the stuff I've tried. I've built most of the engines that guys think about trying and engines don't have computer simulators or read magazine articles.
You have to use a little engine builder logic with some of this stuff...for instance, on heads that will do the best at .550" and .600" lift, you should use a cam with net valve lift in that range and use a lobe that will allow a good amount of flow at lower lift as well.
For entertainment purposes, here's EA's results based on your specs:
302 - 372 hp @ 7000, 313 lb-ft @ 5500.
331 - 379 hp @ 6500, 336 lb-ft @ 5000.
With increased displacement, you will need more cam. That's a standard result that you can count on and is reflected here by the peak hp rpm drop. With increased stroke, torque goes up.
That's why I'm not a fan of these engines...a 375 hp 302 can be done with a set of AFR/TFS heads and a much lower peak, with more torque to boot. My street/strip 347's with AFR 205cc heads and a mild solid roller on pump gas will make 490hp @ 6500 with a 650 carb and about 450 lb-ft of torque.
Both are single pattern cams, they have similar lobe lift, similar durarion at 0.050" and the same firing order .... so you could use either cam in either motor.
But the original 289HP cam had longer ramps (310° duration versus 290° duration for the Boss 302), giving the cam 82° of overlap whereas the Boss 302 cam only had 58° of overlap. All of that overlap was no problem for a small valve motor like the 289, but it would have a terrible impact on the low end performance of a big valve Boss 302. So a Boss 302 cam would work great as a street cam in a 289HP, better than the original cam in fact. But the 289HP cam (as originally spec'd) would not make a good service replacement for the Boss 302.
Perhaps at some point in time the Boss 302 cam replaced the 289HP cam and became a service part for both motors? That would make perfect sense to me.
I bought a service shortblock form Ford, with the D1
August 8 2012, 4:25 PM
Boss 302 shortblock. I still have the NOS replacement block, pistons, rings, crank, but sold the rods years ago. I was planning on using the block for a stroker build, so the rods were unimportant to me at the time. I have both the '69 and '70 Boss 302 heads complete, and a NOS Boss 302 intake with the mis-spelled firing order on it. Lots of parts just sitting, waiting on motivation, and a donor car. I have just about given up on finding a clean Boss 302 car for these parts. Joe-JDC.
I want to use this car as a fair weather driver most of the time... Be able to go to the mall and not worry... That's why I went with a smaller cam... 271s... 225@050 232@050 thinking it would drive well and still pull to 6700-6900...
Then take it down the 1/4 mile every once in awhile and pull of at least a respectable time.l for today's car. Mid 12s... Low12s..
Basically what a stock 2012 boss 302 can pull off...
Um... I wanted to go solid flat mainly because I always used them and liked them... Never really was a hydro guy...
I think it was pointed out elsewhere that you need less overlap for these big ports. A huge duration split never is a good idea for the street, but especially in this situation. I would aim for a single pattern cam, with lots of advance in the cam timing.
....on how much you add. You can add a tinkle of it to help with blowdown, but if you add too much, you get into lots of overlap and reversion.
I've found that a duration spread helps on race motors and dynos, but street cars really love the single pattern cams. Unless a customer specifies that he will be going to the track, I won't add exhaust duration or I'll add a very small amount.
that link has alot of info on almost every off the shelf cam... it weird becasue it gives you what he uses and all that.. not on of the cams is showig a peak torque of 313... maybe his info is way off check it out its strange...
whats very interesting is look at the bullet grind.... it has to be way off... saying over 400 torque at 4500!! granted its a solid rolelr but still
I wish engines made the horsepower and torque that they made on some of these programs....it would be awesome.
Those results are not typical to the real world...and it's always better when you can find ACTUAL dyno results.
I did find an article where they dyno'd a Boss 302 in fairly factory trim. It made 372hp and 325 lb-ft of torque. Keep in mind that when you add cam to raise the peak or add horsepower, torque usually suffers and the peak torque rpm goes up.
With the 1.73:1 Cleveland rocker arms the gross valve lift would be 0.572", net lift would be 0.550" (0.022" lash)
Overlap is 62° ... the original Boss bump stick was 58° ... so you're in the ball park there. Like most modern cams with tight lobe centers the exhaust valve opens later than I like, 75° BBDC. What this means to you, the motor shall need a low restriction exhaust system to prevent the torque curve from falling off like a brick at high rpm.
302 .030 over, 9.5:1, small port iron GT-40 heads with less than 200 CFM intake flow, dual plane air gap intake, 600 CFM double pumper, 226/230 Crane 110 LC hydro flat cam. 4.56 gear, 4500 stall converter, 28" tire, car weighs 3250 with driver. Runs 8.00 1/8 mile in Dallas (about 750 MSL). That's about 12.5 in the quarter. And the car is way bigger than a 79 Mustang.
Put a 347 under those heads, make the compression around 10:1 - probably custom pistons for that - and run a 230 something intake cam. Pay careful attention to all the details - deck, piston-to-wall, bearing clearances, bore finish, quality of parts, etc. IMHO - If you can't make that go mid 12s in that Mustang, you've got too little converter or a messed up suspension. Or a dead elephant in the trunk.
I think what brent is getting at is the gt40 heads dont flow 260 plus, BUT they have alot more velocity... i think what brent is saying is that that gt40 headed 302 will be up 40lbs or torque over a boss 302.. corrct me if im wrong please... but maybe the top end charge will get me there... im going to give this a try and see how much of a dog im going to end up with... maybe a custom cam from someoe who knows the B2's is in order...
i dunno im trying to learn... i just like be different it seems haha
None of my engines are cookie cutters and I too love the higher revving stuff. However, I like the higher revving longer stroke stuff...hahaha
The issue is indeed the cylinder heads. The valves are big. The ports are big. It takes a lot to get all that air moving and moving quickly. Velocity is paramount and you would be surprised with what you can do with a peanut port.
I would do the 347 in a heartbeat....add as much stroke as you can, the crankshafts are all the same price. Never pass up on cubes. The 4V heads are big enough to feed anything up to 410 cubes easily and a 347 will rev like a chainsaw.
No engine is "magical". You put air and fuel in, you get horsepower out. You manipulate each part until you get the result you want.
Before you know it you'll be talkin' about maximizing the output of internal combustion engines and stuff like:
(1) High Thermal Efficiency (like that shallow 351C combustion chamber nobody understands)
(2) High Volumetric Efficiency (large valves made possible by large bores, large ports, high ports)
(3) Low Pumping Losses (large valves & large ports, wide open induction & exhaust systems, running the crankcase under a vacuum)
(4) Low Friction (shorter strokes, small crankshaft journals, thinner/low tension rings, high r/s ratios)
(5) High Piston Speeds (shorter strokes & higher rpm)
Instead of building glorified Cummins Diesel motors and calling them performance motors (small low rpm ports & long strokes), you'll be wanting to build wide powerbands with heads tuned for high rpm and cams & induction tuned for the lower powerband. You'll probably even consider matching the crank arm leverage of your motor to the weight of your vehicle & the traction of its tires.
Use the common 5.7 rod with the 2.87 stroke, with a
August 9 2012, 6:28 AM
1.88" journal, and you would have a high rpm monster. Back in the late '80s I worked with a major racing team on the development of the A-3, C302B heads, and I asked what would be the ultimate bore/stroke combination for a SBF. That is what was considered the best of both worlds at that time. 2.0" journal/5.7 rod/2.87" stroke/4.125 bore. 2.2HP/CI was commonplace in GTP/Trans AM racing. Joe-JDC.
A 3.0 stroke and a 4.125 bore would be awesome... Just the block ($1500) isn't in the cards right now...
Wish it was!!
I might go back to my original plan and just build a regular old boss 302....
Just a tad more cam.... Idk see why if a 1970 mustang can go 14.60 with 3.50 gears... That a 300-400lb car less weight with 4.30 gearing can't hit 12.50 with more cam and tuned properly...
Idk well shall see.. Still up in the air about which cam to run... But thanks for all your guys help!
I'll report back with what I find....
I know ford used to sell the Cobra jet cams over the counter for the 351C and said it was worth 29HP over the stock cam... now melling makes a repo of it i beleive...
Is there such a thing as that with the boss 302? A over the counter performance grind they offered? I may cuz go like a stock boss 302 build with headers and a little bit of cam... should push my car intoothe 12s and still be 100% streeible...
(might have got lucky and found a old roush boss 302 intake)
Ford never offered a "hotter" street cam for the Boss 302, just a racing cam. However, they offered a hot hydraulic cam for the 289/302/351W that some guys replaced their solid lifter cams with. More on that later.
The published factory cam timing events were based on measurements at 0.014" tappet lift, whereas the "advertised duration" of modern cams are "usually" measured at 0.020" tappet lift. This means the factory cam may appear to be a little bit bigger than an equivalent modern cam.
Having written that, the Boss 302 factory cam had 58° of overlap, it opened the exhaust valve at 86° BBDC, closed the intake valve at 76° ABDC. The advertied duration was 290° for both lobes (single pattern cam) and the duration at 0.050" was approximately 230°. The lobes were ground on centers that were spread 116° apart.
My comments, (1) nobody grinds cams with 116° LSA these days, 115° LSA seems to be as far apart as they are willing or able to grind them. And off the shelf its difficult to find any cam with more than 114°. (2) The overlap is what really kills the low rpm drivability with 4V Cleveland heads. The two big valves share "gases" very well during the overlap period which is a great characteristic for a race motor, but it limits the amount of overlap that should be used for street motors if drivability is a concern. The motor will idle very well with 50° of overlap, but it lopes pretty good with only 60° of overlap. I'd set the limit at 60° for a street motor.
Other tricks that are used to give motors with 4V Cleveland heads good drivability are lots of initial ignition advance (16° or more), a dual plane intake manifold (important), limited intake valve duration (one of the reasons for using split duration cams), and centering the camshaft's overlap period around top dead center. As an example of that last item, for a camshaft having 58° of overlap, the intake valve should open at 29° BTDC and the exhaust valve should close at 29° ATDC. This is the other reason for using split duration cams. This is not so important with small valve motors, but it really helps motors with the 4V Cleveland heads. The exhaust valve should open "around" 80° BBDC and the intake valve should close "around" 70° ABDC.
It should be fairly simple to spec a cam for you, one that combines modern lobes with classic cam timing, one that will have factory drivability while making more horsepower than the factory cam. But I no longer do that publicly here on the forum because some people can't give the same respect to me that I give to them.
Have faith in the 4V Cleveland head's ability to operate over a wide powerband; it will work OK at low rpm, give your motor good drivability, as long as you avoid making mistakes that screw it up.
If you want to use a retro cam I haven't kept up with retro-cams for the 302. If you want to research retro-cams yourself, look at the catalogs for Melling and Sealed Power.
On the subject of retro-cams, back in the 1970s and 1980s I worked on several Boss 302 Mustangs whose owners wanted electronic ignition conversions (they were tired of adjusting dual points) and hydraulic cam conversions (they were tired of adjusting valve lash). There was a factory hydraulic camshaft for the 289, 302 and 351W that had 290° duration and 0.290" lobe lift, equivalent to 0.501" valve lift with the Boss 302's 1.73:1 rocker ratio. That hydraulic cam was every bit as hot as the factory solid lifter cam. Something for you to consider. It can be difficult to identify old retro-cams in the Melling catalog because Melling uses SAE criteria for measuring the cam lobes, which gives the cams more duration. For instance a 290° lobe would probably be rated 300° to 310° in Melling's catalog. But there's no mistaking the 0.290" lobe lift (or 0.460" to 0.470" valve lift with a 1.6 rocker ratio).
Do that little rev-monster while you have the chance. If you don't, you may always wonder, you may always regret not having had an engine that was more fun than the "better" or "smarter" build. Lots of strokers out there, lots of LS motors, lots of Gen I chivvies, not many oversquare Boss 302 types, though. Some of us aren't prepared to make every single engine we put together the way the herd or majority think best. Frankly, maybe some of us just want to piss the majority off. Certainly, that's true with me. I run across people with restored B302s, and they want to call the thought-police because mine has been modified. The big-cube small-block crowd will snicker and obviously think I'm stupid. That's alright. If their block is still living and giving pleasure to it's owner at 42 years old, they can say I've wasted my time. Personally, I've never seen a block that's run a lot of stroker time last longer than 5-10 years, at the outside.
I've run Boss 302 stuff for 37 years, and have yet to be truly disappointed. Sure, I run longer stroke stuff for drag or street fun, and smaller port/valve stuff for regular transportation. Those are more effective in their respective range of use. Nothing is more FUN for me, though, than a little cube screamer that comes on in the high side like the early 900cc and 1000cc Kawasakis used to. I can't even begin to estimate how many thousands of miles the old antique'70 block & heads have done at 7000-8000+ RPMs. Waste of time and money? Not when you listen to that beautiful symphony of sound. Not when you occaisionally send some big-inch small-block guy home to count his cubic inches after your top-end charge.
Opinions are great things, and it is good to be able to share them around. We are fortunate to have some really talented, experienced and crafty people on this forum, who are willing to share their opinions and experience, but why does anyone feel they have to be on a do or die mission to convince someone to change their fundamental build to make it the "right" way? Especially if the builder has stated what they want to do, why they want to do it, and are just asking for tech help on that particular kind of build. I am not singling anyone out with that question, because lots of people do it.
Difference is good, isn't it? Otherwise all we'd be talking about would be LS motors, or 427CI Clevelands, or 363CI SBFs, or whatever. No one would ever buy a crank with less than 3.4 inch throws. Any build with greater than a 1.58 r/s ratio unthinkable. Yuck. What a boring universe that would be.
A Visigoth explains the sack of Rome: We wanted art, literature...culture! We're sorry we broke some stuff.
turns out my boss 302 block needs one sleeve other then that its fine... (have)
stock 302 crank (have)
set of 5.4 rods
set of 1.3 comp pistons (have)
4v cc heads unported (have)
roller rockers (have)
cam... something just a tad more bigger then a stock boss 302 and more modern... thinking around 232/235 duration at 050. 590lift 020 lash
something just a tad hotter then a stock boss 302... anyone know a off the shelf solid flat that will work in this case?
1 7/8" headers (have)
hoping to be a decent street car... almost behave like a off the showroom floor boss 302... just hotter...
intake... still undecided.. maybe a track boss with lots of port work ($400)
I have a Track Boss 302 intake that I ported for a similiar
August 11 2012, 8:54 AM
build many years ago, but it is WAY TOO BIG for your needs. It has the 2V port size, but flows 440cfm average. You could buy the Edelbrock Clevor intake, and grind off the Edelbrock name, and call it good. Joe-JDC.
I have used the old Crane 364681 several times, but it is quite a bit nastier than what your stated goal is, Jim. In my experience, it makes max power right at 7,000, and max torque at nearly 5,500 RPM. With 1.73 rockers it has .597/.618 lift. Duration @ .050 is 244/252, and centers are 105/111. Gives about 440-465hp with good single plane intake, like the tall Roush, and with the Weiand Tunnel Ram.
The Crane 363841 is a nice cam for your stated goals. .553/.576, 238/248, 109/119. Not nearly as radical as the circle track cam above, but it has a wider powerband.
I have even tried the old Ford 351 solid M-6250-A333 cam in a Clevor, to see if the firing order switch made much difference. The specs are very similar to the 363841 Crane.
For the latest build of my B302, I went to Bullet for a custom grind solid, but it is really nasty. For the 308 Clevor I am currently working on, I am going to get a custom grind from Cam Research/MPG, as they are one of the few that still actually run these small cube beasts.
If you don't want to go the custom grind route, I think the 363841 Crane or A333 Ford would be good choices for what you want. They don't have all the latest advances, but they still work really well.
Just an opinion, but I would stay away from the factory intake. It will work okay in a near stock build, but you will get quite a bit better results with a B&A (street or track boss, depending on your wants), Roush, or Weiand Tunnel Ram. I assume you don't want a TR, but... I have not yet tried the Edelbrock Clevor intake, but if it runs true to form, it should be a fine choice up to 6,500+. I just can't see using a dual-plane on a B302, for anything over a stock build. The factory used one for the same reason they used one on the B429 & B351; to tame the beast for emissions, driveability and warranty issues. The B351 worked well with the factory intake, I admit, but certainly not to it's potential. And on the other two bosses, it was like a castration, almost. Opinions will vary, so take mine with whatever amount of salt you think appropriate.
A Visigoth explains the sack of Rome: We wanted art, literature...culture! We're sorry we broke some stuff.
I'm liking the second cam spec. The milder one. I'm having one problem the only crane cam I'm finding with that part number is only having 512/533 lift? Am I looking up the wrong cam? Duration is correct though... Weird...
Oo wait... That's probally with a 1.6 rocker not a 1.73.....
That will make the lift taller... I think that's where it comes in...
Didn't you say you wanted around the same peak as the original cam? A factory Boss 302 peaked at 6800 with the factory 228/228 cam. If you add 10 more degrees and a ton more lift over the stock cam, you're going to do one of two things: raise the peak way higher, or raise the peak higher, put the cam out past the range of the heads, and make for a very soggy bottom end. It's a tendency for cams to be picked that are way too big.
I've told you what I would do and even gave you the lobe numbers.
Again, you have to figure out what you want out of the engine. You first started at 7500, then you were down to about 6500, now we are up to factory 302 stuff. Be honest with yourself as to what you want. It's always better to go smaller than bigger but guys always want to claim the big numbers. You've got all opinions from mild to wild so you just have to decide. For 302 inches though I would stay conservative.
crankshaft. You have stated you have a stock 302 crankshaft. Which one? Early 302, Boss 302, 5.0 crank? I would strongly advise you not to consider building a Clevor with anything short of a Boss 302 forged crankshaft if you are planning to turn it over 6500 rpm for any serious racing, or street usage. A stock crank will handle 6500 rpm for a while, but it will need to be perfectly balanced, and have good rods, lite pistons, and neutral balanced flywheel/balancer. If you plan to spin it to 7000+, then you need a forging, period. The mexican block is decent, but it will only support 7000 rpms for a short time without a good girdle, and perfect balanced parts. JMO, been building Fords since 1962. Joe-JDC.
A street cam, one step hotter than the factory cam.
Not bad for off the shelf. The valve lift listed below is "net" lift, the gross valve lift is 0.553"/0.576". Only 55° of overlap. The overlap period is fairly well centered around top dead center. The exhaust valve opening & intake valve closing are in the sweet spot. I think you'll like it.
On the subject of intake manifolds, I would start with a dual plane then upgrade to a single plane if you decide you want more pull on the top end. That way you'll know how how much bottom end you've lost in making the swap. I think you'll be best informed that way. Friendly advice. I won't bust your balls if you deicide to do otherwise. I just want to listen to you & help you achieve what you want to achieve.
That cam George listed is exactly the one I thought would get you where you want to be, Jim (2nd one I listed), although he quoted it with the 1.6 rocker ratio I believe. Not that radical, wide powerband. The last one I built with that cam really didn't need to be wound any higher than a stock B302 - 6800-7000 max (with no factory style rev limiter, anyhow).
Joe D. prolly has more experience than I, but I never had any crank problems on 302s up to 7500. Just use top quality bearings and a good machine shop. What I had problems with was the weaker blocks...'77 or '81 and up, I think. I agree with him that a main girdle would be pretty much a necessity for any non-Boss/non-aftermarket block. Fairly cheap insurance to keep stuff from wiggling around in the basement and causing a block failure. For non-forged, I think the '68-'69 cranks are great. Good balance job and good, non-cheapo balancer/damper should keep it happy for all but balls-out serious racing. I would shoot for 10:1 compression at least. With that cam, I believe you would have no problem running even 89 octane gas, with 10:1 static compression. I like 11:1 or close to it, as the chambers are good for it with a cam like this or bigger, but you would have to run at least 91 octane gas.
Believe you have the makings of a fine little Clevor/Mock Boss.
A Visigoth explains the sack of Rome: We wanted art, literature...culture! We're sorry we broke some stuff.
My brother had a 70 boss 302 for a while, he let me drive it on a couple of occasions. It was a really fun car to drive, but the best part was that it was a stick. An automatic would not make the car nearly as fun to drive, and the engine would not work as good with an automatic. I had several friends that had boss 302's, a couple of Mustangs, and a couple of Cougar Eliminators. The first thing they did was disconnect the factory rev limiter that was set at 6150 rpms, and it made them even faster. These friends often raced many big block cars and blew them away because the big blocks overpowered their tires. Contrary to what the naysayers said about better combos, I would not let anyone talk you out of it if thats what you want to build. A slightly bigger cam and headers would be a plus but the rest of the engine was well engineered for its time. Maybe George can remember that Ford,through the Muscle Parts program, offered a hotter cam called the C7fe that was for the 289's. Does anyone remember the specs on that cam? I had a friend that had that cam in his 64 Faitlane with a 289 Hi Po that made it run pretty good back in the day. Even back in the 70's guys were taking a decent small block with a 4 barrel carb and adding slicks, headers and gears and could get their cars to run in the 12's. Even somewhat fast by todays standards. I know this is 2012 and technology has changed but it all goes to show that maybe we sometimes out think ourselves and don't keep things as simple as they used to be.
The C7FE cam was also called the GT40 cam, it was a very, very popular small block
Ford cam. It was designed with the small valve 289 heads in mind, not the 4V
Cleveland heads. The design criteria is just the opposite of what a street motor with
4V heads needs, but admitedly this cam was designed for road racing & endurance racing.
Part number C7FE-6250-A
Motor: 289/302 Ford V8
318°/304° advertised duration
311° average duration
Exhaust valve opening = 82° BBDC
Intake valve opening = 52° BTDC
Exhaust valve closing = 42° ATDC
Intake valve closing = 86° ABDC
250°/250° ESTIMATED duration @ 0.050
0.550"/0.546" net valve lift (1.73:1 rocker ratio; 0.020"/0.025" lash)
108.5° lobe separation angle
Int lobe mathematic centerline = 107° ATDC
Ex lobe mathematic centerline = 110° BTDC
The lobe lift is 0.330". The valve lift figures were computed using a 1.73:1 rocker ratio.
I always list "net" lift, which means I've subtracted the valve lash from the theoritical
valve lift numbers to arrive at the lift numbers I've listed. That's how Ford used to do it.
This cam had quite a bit of valve lift for 1967.
By the way, I suspect this is actually a single pattern cam. The intake & exhaust duration
are listed as two different values because the intake lobe data was measured at 0.0125" tappet
lift, whereas the exhaust lobe data was measured at 0.0155" tappet lift. Notice Ford lists
differing values for intake lash & exhaust lash.
put as long a rod as possible, and as short a piston as possible with quality ring package, and you can make more torque, run less timing lead, making the engine less prone to detonation, and have less side loading of piston skirts. Anytime you can run less timing for a given compression ratio and still optimize the power, you will be less prone to detonation, and can even get by with less quality fuel. With the acceleration rate of piston as it nears TDC, and as it leaves TDC you will have a slightly longer push time after ignition, which in theory will produce more torque. A shorter rod will accelerate quicker towards TDC, and quicker away from TDC, needing a slightly longer lead before firing so that it fires at the proper timing for max power. A too large port seems to work better with a short rod, since it helps accelerate the incoming air charge. What it boils down to is that you need to find the best combination for your particular head/intake/CI/flow requirements. I always build with the longest rod possible, and it has stood the test of time for me---others swear it makes no difference, so you build what you can, and just go with it. I have built many 351C/B302 style engines that made upwards of 2.2hp/ci, and I have been very successful with the long rod builds. JMO, Joe-JDC.
Re: Several points of view, but a simple answer is
August 15 2012, 8:15 PM
Well, guess it's like lotsa other things...I ain't gonna get a concrete rule of thumb, 'cause the rule changes with every different combo. Oh well. I always thought success was a good example to follow, and the Ford Indy engines, early F1 and LeMans 302 configs are about as big in the success department as I can imagine. Never had a particular problem that I knew about using long rods, just don't want to leave a lot on the table, if I can help it. Thanks for another lucid opinion, Joe.
A Visigoth explains the sack of Rome: We wanted art, literature...culture! We're sorry we broke some stuff.
The Bud Moore Race Team tryed building a 351 cleveland destroked to 302 for the 1970 Trans AM race season, they said the engine idea was droped because the engine could not match the Boss 302 power with a destroked 351. I know a street engine is not intended to pull max power but Bud Moore racing were the first guys I herd say the short rod Made better power with 4V Cleveland heads.
I've always wondered what the break-even point is on long rods, Tin. I'm sure some smart engineer or racer knows. The Bullet guys were warning me that the cam would "act bigger" with the longer rods in my B302. You're saying longer rods take away from the ability to pull on the big port. I use longer rods occasionally, almost always on endurance type builds, in fact, and have never heard a consistent argument to convince me not to. Sometimes seems like a lot of opposing logic at work in this area, but there must be an overall rule of thumb somewhere.
I've often wondered what the overarching reason was for Ford using 5.315 "Indy" rods in the 302 that won LeMans twice: Same as the Indy motors, that the enhanced durability from less rod angularity over-rode whatever the bad points were? Always been curious. I always thought the 351C had a "compromised" setup, 'cause it's R/S ratio is so close to an SBC's. A very good possibility that I am all wrong in that, though.
Not that I would ever use an SBC as a model of good design (Hmmph!!), but even a 5.4 rod in a stock stroke 302 has a ratio of 1.8:1, while the 283 has a 1.9:1 ratio. Would a 283 be considered over-endowed, but gets by with it because of it's laughably puny air flow? Interesting topic to me.
A Visigoth explains the sack of Rome: We wanted art, literature...culture! We're sorry we broke some stuff.
I am in agreement with Joe Caine, and my theoretical street & sports car motor would have at least an 1.8:1 r/s ratio. But I'd like to remain focused on what's useful for Jim's Boss 302 street motor. I think durability is the #1 priority of a street motor, drivability the #2 priority, and power the #3 priority. A long rod will reduce thrust on the cylinder walls, reduce friction, and result in more power to the rear wheels each and every time. Would Jim notice the difference between a 5.4" rod or a shorter rod in terms of drivability or low rpm power in his street motor?
I've only driven Boss 302s with the standard length connecting rod, so I'm not equipped to answer that.
I also don't know if reducing cylinder wall thrust is as important of a consideration for a Mexican 302 block as it is with a thinwall Cleveland.
Baker did a whole series of long rod posts...I'll add them here if anyone is interested.
For a B302 street engine that literally can't be optimized for a lot of things (pump gas, mufflers, hot plugs to prevent fouling, low compression, etc. I don't think either rod length could be discerned. JMO.
I could be wrong but wasn't the prostockers destroked??
August 16 2012, 10:46 AM
I've read quite afew articles on r/s ratios and most guys consensus is its a turkey shoot! It is mostly application orientated. I do beleive the old prostockers (some anyway) destroked the cmotor to end up at 340 cubes. Lee hunter was one of them and the theory I guess is a harder pull on head after tdcas piston speed is accelerated. I would say that is maybe the existing parameters of the little boss as it sits. Maybe those old engineers were smarter than we give them credit for. The bbf follows a similar criteria.
back then NHRA played with the CID/weight breaks/wheelbase so much in Pro that everyone complained, which later lead to the 500" rule. See the 500" rule line item below. Destroking was primarily used to 'fit' a specific chassis/weight into the class, which lead btw to the famous Gapp & Roush 4-door Marverick!
Yes I do know that was the case but it is no denying that that combo made serious hp. Now was it maybe that rule made them stumble upon a combo that worked? The 360 engine didn't make anymore power? Or I should say didn't make much more.
Bob Glidden also said the 340 size was the ultimit size to get the most power per cibic inch from the 351 c head as he had it configured. Pounds per cubic inch was a key factor! Making the most power with the combination Won or lost races.
dad ran a 331c.i. cleveland that ran 8.70s-8.80s at legal weight. it was his 1st pro stock engine(the only one he didn't build) that he bought from roush at the end of '75. according to jack, it was one of the "taxi" engines. dad loaned the rotating assy to dyno don at some point for him to make a race as he was waiting on his crank from HTC. never got it back. not sure if he would remember any specifics on it or not. those heads are the ones on the car right now. not his "good ones" but very good...as previously stated, the c.i. of these engines were built for a specific rules package that NHRA was always jacking with(for clevelands anyways). that's why he built his clevor "that changed the rules" going from "weight break is determined by the block" to "weight break applied to the heads".
Tony Marbury (Login tmarbury) Member 22.214.171.124
also don't forget the 73 heads
August 17 2012, 12:55 PM
They are free or damn near, smaller valves open combustion chambers, works great on a 69 flatop 302, but if you order pistons, you can select any compression ratio you want. All your research of valve size drivabilty and so on was and is already done for you, by ford. ( smaller valves ).
Runs well you can back up a hill in reverse with a manual trans with out slipping the clutch as much, and top end performance is there, unshrouded valves, the works. I called it the poor mans Boss.
reducing the bore isn't as efficient for moving air in and out as shorter stroke at high rpm is it? at least that's how i have understood it. longer stroke takes longer to fill the cylinder? goes back to application. how tight are you gonna wind it? this 331 they'd leave the line at 9000+ rpm. obviously not good for a daily driver....
i have read Dyno Don like large bores on his cleveland to unshourd the valves and make the heas flow even better. i think he used 4.08 bores , thats why they furnas brazed the block back then to get the large bored. Granted i wasnt there. just what i read. I would like to know how much more power he gained doing it
dyno don, glidden, g&r, and perhaps others that used the stouter aussie blocks, bored, sleeved, furnace braized, and finish bored to the max. quite ellaborate back in that day. there was behind the scenes help from ford on these. i heard that it ran $2500-$3000 back at that time for one of these blocks for the other guys that didn't have "the ford connection". that was a chunk of change in the 70's. dad never had any block issues and felt it better to spend the $ elsewhere on the car so he never had one done. there wasn't but a place or 2 in the country that had the capability to do it if i remember correctly. i have never seen one of them but would love to check one out. anyone have pics of one?
When you are trying to turn the engine to a rediculess high RPM you have to think of bearing speed and piston speed,Long stroke don't work real well at 10000 rpm. the engines that are built to day are intended to keep the RPM down so piston speed is not a problem. If you have two engines one with 3 inch stroke and one with 4 inch stroke the piston with 4 inch stroke has to travel a lot faster than the one with 3 inch stroke at the same RPM!.
Luc John Feilla (Login Luc69stang) Member 126.96.36.199
Stroke that Boss 302!
August 27 2012, 1:51 PM
Sorry, but I just have to dissent with the way this thread is going in terms of the Boss 302 build. I think a lot of people are getting nostalgic around the Boss 302 and forgetting that it was not a very fast or very powerful engine. Period. Im sure it revved like crazy and sounded great, but lets remember that it couldnt break 100 MPH in near stock trim. Check all of the magazine reviews, Im sure the average is around 95 MPH, and that says a lot. It could not get out of the 14s in the quarter mile. This was a combination, as we all know very well, that was created to satisfy racing standards (Trans Am). It was not designed for the street. Id take a Boss 351, or a regular 351 Cleveland for that matter, over a Boss 302 in a nano second. The heads love the extra cubes for a street driven machine.
Given the above, I just dont understand why we are advising anyone to build a 5.0 liter motor with our beloved Cleveland cylinder head when 351 cubic inches is at the very low end of the range of what that cylinder head likes. 400 cubic inches is not even close to being too much for Cleveland heads. Now, the gentleman that started the thread wants to run 12s but have a good idle, vacuum, 80% street driven, and run 12s? With a Boss 302? Cmon. Thats not easy unless you have slicks, 4:30 gears, a big cam..a little nitrous. It can be done, but not within the parameters laid out.
For an 80% street vehicle that you want to run 12s with I think it will be much easier all the way around with more cubes. Stroke that motor a 3.25 stroke is the minimum to give it some grunt. Personally Id stroke it to 347 cubes. If I had more money then I would buy a Ford Motorsport block and bore it to 4.125-4.150 and have to decide whether to use a 3.25 or 3.4 stroke.
Im just afraid that he would be disappointed after spending the time and effort to get a motor that would probably not perform to the standards that he set. Just my opinion.
95 mph? Luc John is that top speed or 1/4 mile speed? At 95 mph in 4th gear the Boss 302 motor would only be turning 4400 rpm, in third gear that would be about 5800 rpm.
In regards to acceleration, I've always had the impression that with the rev limiter unplugged and at least the same 3.91:1 gears as the Boss 351, the Boss 302 would have given the Boss 351 a run for its money in any acceleration test. That's not pure conjecture, I've driven both. The Boss 351 made peak HP at about the same rpm as where the rev limiter kicked in, but the Boss 302 made peak HP in the range of 6800 rpm, therefore the rev limiter really hurt the performance of the smaller Boss. It really needed stouter gears than the 3.50:1 gears it had off the show room floor if you wanted it to perform at its optimum. I've never understood why Ford encumbered the 1969/1970 Boss 302s with 3.50:1 gears when they were willing to install 3.91:1 gears in the 1971 Boss 351 a year later.
In regards to top speed, I've driven a couple of Boss 302s wound out at 7000 rpm in 4th gear, with the speedometer needles wound way past the 120 mph mark. I didn't feel comfortable taking the motors beyond 7000 rpm, and the front end of the cars were getting dangerously light at that speed. Plus that speed was way beyond the speed rating of the tires. So I stopped at 7000 rpm. The rev limiters were unplugged, heavy duty points or Duraspark ignitions were installed, and headers were installed; those were the only changes to the motors.
Luc John Feilla (Login Luc69stang) Member 188.8.131.52
1/4 mile mph
August 27 2012, 10:13 PM
My experience is that the Boss 302's were good performers but you had to rev them higher to get performance out of them. I agree that they need 3.90-4.11 gears. The 351 Cleveland's were just better all around on the street or at the track. That was in the late 70's and early 80's.
Again, if you go back to the old magazine tests the Boss 351's comparably equipped were better than the Boss 302's. I think it just has to do with cubic inches; the big Cleveland heads have a certain amount that they like for a street application. At the track it doesn't matter, we can get a Mazda to turn 8's if we want to.
Ak Miller did a series of dyno tests of both the Boss 302 and Z/28 302.
He started with a stock crate motor fitted with long tube headers (with
primary lengths between 30 and 34 inches) but no accessories or rev limiter
and ran it for 6 hours on the dyno at variable loads to break it in. Then
a series of runs were made to the carb and ignition. The best pull resulted
327 HP @ 6600 RPM
290 ft-lbs @ 4000 RPM
On a 351C-4V, we recorded losses of over 30 HP and 30 ft-lbs going from
headers to cast iron manifolds. Factor in the drop SAE gross to SAE net,
and, in stock form, the high compression Boss 302 didn't make much more
power than a 1987 5.0L HO (225 HP, 300 ft-lbs net) with 9:1 compression
and 1.78" intake valves. Unsurprisingly, a 1969 or 1970 Boss 302 ran the
quarter mile in about the same time as a 1987 Mustang GT (mid 14's).
BTW, the stock Z/28 302 was given the same break-in and similar long tube
headers and made:
325 HP @ 6800 RPM
286 ft-lbs @ 5200 RPM
Miller added a ported heads, a DOZX-6250-B Trans Am cam with upgraded
valvetrain (titanium valves, stiffer springs, roller trunnions) and dual
Autolite in-lines on a Doug Nash independent runner intake and the Boss 302
476 HP @ 8000 RPM
A switch to a large bore Doug Nash injection set up made:
491 HP @ 8200 RPM
345 ft-lbs @ 6200 RPM
An experimental cam was later fitted and said to have made 500 HP @ 8400 RPM.
The Boss302.com site has the text of an interesting interview about the
Trans Am Boss 302s:
Q: Should pucks be installed in Boss 302 heads? On the flow bench it seemed to
help, but it's peaking at 5400 rpm on the dyno. Any advise would be helpful.
A: Any build up of the floors will help. We have welded the intake and exhaust
ports all the way back to the short turn radius. This fills the port about 30%.
The intake ports will flow the same total CFM but at a much higher speed and
increase the low end. On the exhaust port you will pick up another 20% over
the best porting methods. The BOSS 302 T/A heads used by P.J. and Folmer had
the floor of the intake ports raised when the heads were cast. That is why the
mini-plenum manifolds have smaller ports than a standard BOSS 302 head.
In our testing, 4V heads have responded favorably to increasing displacement
with less timing required and higher volumetric efficiency. Note it's not
that hard to make over 500 HP (with similar torque) with a 10:1 compression
393C or 408C with iron 4V heads and a relatively mild street cam that peaks
by 6000 RPM.
...that seems quite a bit off in my own experience, Dan. I don't recall ever seeing a well-tuned B302, stock or stock rebuild with headers, making less than about 380. Plus a recent set of tests done by an admittedly Chivvie-biased magazine had much more positive results than Ak apparently did:
Boss 302 VS DZ/Z28 302 http://www.hotrod.com/techarticles/engine/hrdp_1001_muscle_car_engine_shootout/ford_boss_302_chevy_dz_302.html
Also, if you look at page 4 of that series, the Boss 351 made a whopping 11 more HP than the 302. Naturally, the 351 made it at more "usable", "streetable" or drag-friendly RPM, especially when you consider the torque (70 more lbs @ lower RPM). Bottom line, two great engines, both overdue for recognition. Nice to see Hot Chevy/Camaro Craft show that they gave nothing away to any siamese port engine.
Nobody is arguing that the 302 is better than the 351. Two different power delivery methods, that's all. You want an easy to drive car with good power, cubes are always better. You actually dare to like a high-strung, small inch mill that will endure many miles at high RPM, why not, even if you know it is the "wrong" way to go about it?
Harder to get a streetable car that will run 12s with that small, revvy engine, but not that hard, in this day and age. Car Craft's July 1972 issue had an article wherein they bought one each used '69 Z/28 and '70 Boss 302 and mildly modified them for 1/4 mile improvements. Bolt-ons only (but stock intake, at least for the Boss), and of course rear gear changes. The Camaro eventually ran a 13.02, and the Boss ran 12.93. With a modern cam, etcetera, I will bet that Jim can get his ends achieved without much difficulty. Not as easily as with a 3.4, 3.5 or 3.98 stroke, but that's part of what some people like about it.
A Visigoth explains the sack of Rome: We wanted art, literature...culture! We're sorry we broke some stuff.
...it's just the hard way to get to a "daily driver" with high vacuum, good street manners, etc.
Most of replies on here get some strange looks, but when someone says they want a daily driver, I automatically go conservative. I know how hard it is to get big power out of a 302 inch motor, especially with big fat heads....and getting big power while trying to make a princess out of the engine makes it extremely hard.
Thanks Dan for referring us to that Boss302.com website. That has a lot of good information. I particularly liked the camshaft simunlations.
Look, regarding this whole to build or not to build a Boss 302 situation; if you have the parts, great, go for it. You can make it scream. I'd take a look at some of the cams on that Boss 302 website, it is very interesting, I'd pick one of those cams. What you have going for you in your late model Mustang is that the suspension/chassis will transfer the power more easily than the first generation Mustangs, so that will get you closer to your goal. I encountered many 1985-1995 Mustangs at the track that ran low 12's naturally aspirated. I'd definitely have the heads "optimized" for your situation and run some of the Cam Research "Stinger" exhaust port plates/inserts to help the velocity of the exiting exhaust charge. The cool thing about a Boss 302 is the "wow" factor, and after seeing some of the cam simulations I'm sure you could get a modern Boss 302 to make more than 400 HP at the flywheel, and that should get you into the 12's. Some of the cams on the Boss302 website had low overlap numbers, also, and that would imply good vacuum and street manners, which is a big bonus. I'd take a look at the Lunati 306A5 which has 53 degrees of overlap, though I'm not crazy about the Intake Valve Closing (IVC) at 62 degrees. The Comp Cams Nostalgia 271+ looks like a heck of cam with only about 41 degrees of overlap; the implied lift is ony around .535 or so, and should be easy on parts. The Crane F-278-2 looks good too, with low obverlap of 55 degrees. The best cam of the bunch could be the Crower 15415 with a tolerable 60 degrees of overlap. Whatever you do stay conservative on the overlap because the big port, big valve cleveland heads with small cubes will suffer all the way around - vacuum and power - with too much overlap.
Good luck, a Boss 302 built correctly will be a lot of fun in a late model Mustang and would be unique and cool. I think if you are careful you can hit your goals.
I am not here to step on anyones toes.
if you only count old school engines, the boss 351 is the fastest small block powered production car.
Yes i am sure a 289 cobra might be faster.
the boss 351 in magazine tests ran 13.80 at 104 miles an hour . I had seen somewhere a modified one with headers and i am thinking a holley car ran like 13.30sat 107.50 mph back in 1970 or 1971.
granted the test car might have been a ringer, but so were all the other test cars the magazines got back then. the boss 351 was handicaped, by 2 things the boss 302 werent. the extra curb weight of the bigger 71 mustangs, and by the junk 4300D autolite spread bore carbs. the boss 351 had the same 6150 rpm rev limiter, the boss 302 was equiped with. anyone thats ridden in a boss 351 that thinks its a dog, the car is not running right. (probably because the carb is messed up) or it doesnt have a real boss 351 engine under its hood anymore. it doesnt take much to get a boss 351 to run. get rid of the factory carb. i would also change the intake. something like a blue thunder, add a 780 holley like the boss 302 had. get rid of the rev limiter. I would also replace the distributor. I like the mallory unilite. put some headers on it. throw on traction bars, sticky tires, you now have a car that will run 12s.
i havent even talked about changing cams. and i can tell you, there are a whole lot better cams out there than the factory cam. ask how i know. I own one.
I installed My stock boss 351 engine in a 3000 pound 1982 mustang using 1 7/8"x 3.0" headers a strip dominator, 780 holley carb 600 lift solid cam and crane roller rockers. this engine had all stock boss heads, pistons, rods, lifters, push rods, crank and oil pump, this car had 4.86 gears and 11.5 28.5x 15 goodyears. This combination run 12.00 et @ 112.25 mph shifting 6500 and crossing the line at 6600. These engines had good potential right out of the box!