(Login 73torino17) Member from IP address 71.37.188.204
I was messing with the timing in the stock car motor today and I noticed that above 4k the oil pressure slowly falls off about 10psi by 5k. All of the clevelands I have built have done this. What causes this?
oil pressure is 70psi cold idle
hot idle is 30 psi and gets to 60 psi by by 3500, and then starts falling off above 4k down to 50psi by 5k.
no lifter bore bushings
restricted cam bearing oil
restricted pushrods
.002 on the mains with full groove bearings
.0025 on the rods and .020 rod side clearance
hv pump with std spring. regulates at 70psi
8qt pan with pickup .25 off the bottom of the pan
* unless you've been using the same oil gusher roller lifters in each build that you're speaking of?
and even if that is the case, 1/4" is justa little too close IMO. once the pump starts getting some good suction going the oil can become a 'coupler' that will draw the bottom of the pan closer yet to the pick-up
what you're seeing at 5k is an 'out of oil' scenario for whatever reason
there'll be phantoms, there'll be fires on the road... and the white man dancing
The second number means the most when the engine is hot...I like to run a 15W-50 or close to that for my hipo stuff.
I've seen the same deal that you've seen on the dyno, but I've found that when you add viscosity or cool the oil down, it will hold its own. This especially helps with the hydraulic rollers as it will help keep the lifters pressurized.
I do a lot of hydraulic and solid roller stuff and I've never used lifter bore bushings. I run HV pumps, restrict oil to the cam (either by screw-in restrictors, or the restricted bearings that Tim sells), and set the bearing clearances at about .001"/inch of journal diameter. My mains are usually between .0027-.003 and the rods are usually around .0025". Now granted, most of my engines have hp peaks that fall between 6000-7000. For the guys turning to 8000 rpm and higher, you may have to get a little fancier...
What's in it for lifters and cam? 10/30 weight too light
July 8 2012, 12:49 PM
.25 clearance seems too close but depends on pickup geometry and relationship to bottom of pan (level). Restrictors in pushrods probably not a precise means for oil control. How much oil is collecting in valve covers? Need more specific details of what exactly is in the engine for all restrictors, lifters, push rods/restrictors and size of restrictor in push rods. lifter/bore clearances? Too many things if data not collected when built, probably start with at least a heavier weght oil -40 or -50, go from there. Where/how do you use the car. Seems as though pump is starving for input flow, pumping dry or restricted at input. not likely, but frothing of oil may also cause issues. is this a street car?
With the 351C ... the drop off of oil pressure as rpm climbs indicates lubrication problems ... it's a classic Cleveland problem. But oil pressure that holds steady as rpm climbs does not necessarily indicate the lubrication system is OK. It is possible to have plenty of oil pressure and still starve the rod bearings for oil. The first question - what's the condition of the bearings when you tear the motor down? That's the bottom line. If the bearings are in great shape, then the problem is not a major problem. If the bearings show signs of inadequate lubrication, then this is a big problem.
In your case the oil pressure is dropping off at lower rpm than normal. Here's some ideas ... I'm just brain storming you understand:
>>Agree with Tin the oil pump pick-up may be too close to the bottom of the pan
>>The oil pump suction line may be too small in ID
>>The oil filter may be too restrictive (Fram?)
>>The lifters you've chosen may be interacting with the Cleveland lifter oil passage in such a way to create this problem
>>Too much clearance between the lifters & lifter bores
>>Aeration of the oil, pan needs windage tray & scraper
>>Oil level in the pan is dropping too low
>>Centrifugal force is causing the oil in the pan to slosh away from the oil pump pick-up during high G force situations (acceleration, braking or cornering)
>>Heat ... the oil is getting too hot and the viscosity/pressure is dropping off
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By the way, I am in agreement with your choice to use the pushrods to restrict oil to the valve train ... assuming your motor is using a hydraulic camshaft & lifters. That's really the only way to do it with hydraulic lifters. It doesn't help at all with solid lifters however.
This message has been edited by gpence from IP address 75.22.49.201 on Jul 8, 2012 5:29 PM This message has been edited by gpence from IP address 75.22.49.201 on Jul 8, 2012 5:22 PM
I wish I could add something - but I've never seen the problem. Which seems kinda unusual after reading. I make sure the pickup is at least 1/4, better 1/2 off the floor. I ran plenty of 10w-30, usual pressure - picked up at the back of the block - would be 35 hot and 60 at 2400 staging RPM, same 60 psi in the lights at 6000. I switched later to straight 30wt, same pressures. Cold would be 70~75 psi.
I set the pickup at 10mm from the bottom of the pan. IMHO 1/4" is too tight.
I have never used full groove bearings(and never will) or a HV oil pump in a cleveland either. If you set the clearances up correctly the engine should maintain 60/70 psi @ full noise.
I drained the oil and left filter on. Then I added 1 qt at a time while I turned oil pump drive with a drill. Took just over 3qts to get picked up, but would cavitate after about 30 secs and 4 qts kept pressure steady. Makes it hard for me to believe that the pickup is .25 off the bottom. I guess, the actual pickup tube is up inside above the screen, how much higher is that?
The pan is a 8qt t shaped pan, And that would explain some of why it takes so much oil to get the level high enough to be picked up. Seems like to much though??
What weight do you guys think I should run given the build? I usually run 10w40 during the race, but have 10w30 (have a bunch to use up) in it right now while I am working on it.
forgot to answer, that this is a stock car motor. 4500-6000 over and over for 30 laps. I am planning on re gearing for 5000-6500, but need to get this stuff figured out first.
Thanks for the replies and suggestions guys. I really want to put a beating on all these chevy cars, and I get a lot of crap from all the guys, cause they can basically build a motor from junk or get any old runner and throw heads and cam at it. Several guys in this class have built sbc motors for about 1k that are more than competitive and have over 40 races on them. My record so far, is 9 races. This was a bone stock high miler out of a 74 elite I put a mild cam and springs in it, and it on race number nine it had an in. valve break under the keepers.
When we dynoed my 436 we seen a oil pressure drop on the high end of about 8lbs after the oil hit over 200 degrees. We attribute the hot oil temps to cemented block and the extremes encounterd in dyno rooms. That's why I preach the cold engine temps so you can keep oil temps low short of running cooler. I'm withe Brent in higher viscosity oil such as a 40- 50wt as this helped maintain my pressure. I also have bushed lifter bores, restrictor kit and rear oilfeed line. I used a Melling hv pump. I think your oil is to light for endurance style racing your in.
This message has been edited by steve.k from IP address 209.91.107.217 on Jul 9, 2012 3:17 PM
maybe you have a cracked pickup or the set-up is not what it once was. Do you actually have a real circle track race pan and pick-up? When you say it's T shape I don't think that sounds right for circle track. They tend to run some pretty fancy baffled/gated right side kickout pans and special pick-ups. Is it safe to assume your pressure drop is under race conditions?
This message has been edited by F0rdmech from IP address 98.175.59.219 on Jul 9, 2012 6:38 PM
the pan is a cheap t shaped pan, but does have some baffling that would help out.
If nothing is mechanically wrong, just that the oil is too thin, what causes the pressure drop at high rpm? Does centrifugal force throw the oil in the crank out through the rods?
maybe cracked pickup, not throwing oil thru rods at high rpm. if it takes 3 qts to prime I suspect something wrong or maybe just too much flat area but that cheap pan/standard pickup not ideal for intended use. Possibly too much oil trappped upstairs a contributor. circle track, high g forces in turns can trap oil where you don't want it, doubt it will be sorted on internet
This message has been edited by F0rdmech from IP address 98.175.59.219 on Jul 10, 2012 7:01 AM
I would not run heavy oil in any engine that uses gasoline, that is usually used in engines running methenol or ethonol because the stuff seeps by the rings, diluting the oil. I like to use Valvoline 10w-30 racing, unless I can't find it. I used to prime all my engines on the engine stand before putting them in ther car. Take the drivers side lifters out of the block with the intake and distributor off the engine and prime the oil pump to see if your oil is foaming up. if it is foamy, then you have a leak in the system because you are sucking air. If the oil isn't foamy then you are probably pushing oil past your lifters, causing fluctuations in your oil pressure.
Denny I beleive you on lifters for sure.I just worked on 2 bbf engines for a buddy.The first one was a iron headed cj 545 that had low oil pressure?After a little head scratching and digging we found that the new solid lifters were leaking inside the bodies.The next engine was a engine he had just picked up with drag car,the engine also a 500 inch 385 block had thrown a lifter and taken out the solid roller stick.The previous owner had replaced cam,lifters and replaced mains.After it was together it would only hit 40 psi cold then after a minute run time drop off to about 15-20?We did some digging and it appears they hand been sold 351w roller lifters?I had a good used set of Isky roller lifters and we stuck those in and now it runs at a consistent 75 psi?It is very important to check these new lifters with a pressure check with intake off as the quality seems to be lacking these days!The engine above may have a couple bad lifters or like Denny says the bores could be at fault! Just some food for thought! Steve
every Cleveland enthusiast laments "it doesn't have a main priority lubrication system". Then we try to patch it with band-aids, and we suffer with incompatible lifters, etc, etc. But some people obstinately insist they don't need lifter bore bushings. I was one of them.
In the 1970s and 1980s the consensus was only solid lifter motors needed lifter bore bushings, hydraulic lifter motors didn't need them. I even owned the kit that Ford sold for installing them, but I still didn't install them in my own motors, because they were hydraulic lifter motors.
But because Denny patiently presented his case for the bushings, over and over, it finally sunk into my thick skull. 16 lifter bore bushings and 5 cam beariing restrictions modifies the lubrication system so that it functionally behaves as a main priority system. Everything else is a band-aid, this is the REAL fix. Look at all the issues the bushings resolve:
(1) Preventing the drop-off of hot oil pressure at high rpm
(2) Resolving the inadequate supply of oil to the rod bearings at high rpm (normally the rod bearings for cylinders #2 and #7 are the first to loose lubrication)
(3) Resolving incompatibility between the Cleveland lifter bore design and modern lifters
(4) Repairing excessive lifter bore wear on high mileage blocks
(5) Preventing excessive oil leakage at the clearance between the lifters and the lifter bores
(6) Controlling how much oil flows to the valve train (solid lifter applications)
(7) Metering the same amount of oil to all 16 rocker arms
(8) Preventing the loss of motor lubrication if a lifter pops out of its bore
(9) Isolating the reciprocating motion of the lifters from the right hand oil passage which also supplies the main bearings. This prevents the pulses and wave action resulting from the motion of the lifters from impacting the oil feed to the main bearings
(10) Modifying the lubrication system, in conjunction with cam bearing oil passage restrictions, so that it functions as a main priority lubrication system
Those who, like me, refuse to install the bushings are fighting over what? The cost is only $400! Guys spend more than that on valve covers. The bushings fix the Cleveland, they fix it right, they fix it once and for all.
In fact, the bushings can be cut a little longer than normal and installed so they protrude above the lifter bore 1/8" or so, making the Cleveland lifter bores more roller lifter compatible.
Hydraulic cams, flat tappet or roller, should limit oil to the valve train via the push rods (downstream of the lifter). The orifice in the bushing should be the same size as the orifice in the lifter, so as not to restrict oil feed to the lifter. This ensures the hydraulic lifter will operate as designed.
that lifter bushings are the way to go on a cleveland, but finding someone around here to do it is very hard. It seems that 90% or better machine shop guys only know sbc stuff, I couldnt even get anybody to cut my heads for dual springs, and had to build my own tool to do so.
And an easy to use exellent set up it is.. Couldn't be happier with how it has worked on my Engine. Just as an interesting side note, I used 0.047" holes in mine which were to be used with a solid camshaft. Ended up reusing a Hydraulic cam with these hole sizes and the lifters work 100% as well as before the block was bushed! You would still be amazed at how much oil flows with even that hole size, I checked numerous times on assembly with oil and then diesel (which mimicks hot oil with the pressure it runs on a mechanical guage when driven from my drill)Engine will hold 50 psi with my drill with every lifter removed and 67.5psi with every one installed. Will still shoot a 1" high stream of oil out of every pushrod hole with the drill turning it to 67.5 psi too. I won't build another Cleveland again with out it, each to his own...
