When you say do I think the intake is sealed. What is the contaminant that might possible be getting into my combustion chambers from a leak?
There is NO coolant getting in or being lost...
No identifyable vacuum leaks...
It is an edelbrock RPM Air Gap intake, and the surfaces were excellent on assy.
I put brand new valve stem seals on it 2 weeks ago out of a victor reinze head set.
I swapped out the seals but did not remove the valves and check for slop in the valve stems due to time constraints and the fact that he said there was only 10K miles on the entire rebuilt engine..
The Cam is a 238/248 from summit. Don't ask me any more cuz that's all he gave me
If its leaking on the inboard side, the gallery side, you could be pulling in some oil vapor darkening those plugs. You may just want to re-torque the bolts on the intake while its running. I did that on a 351W while it was running, and was surprised how the mysterious miss cleared up.
Air Gap intake has no access to the galley really... I mean, when I put the heads and intake on the intake and head surfaces were excuisitely flat and everything mated up perfectly...
Although.... There are 2 bolts on the air gap that Edel say's to ONLY GO HAND TIGHT on....
Maybe that's what is happening... I torqued them with the rest of the bolts.... BEcause the guy with the truck didn't give me any special instructions along wiht it...
Holy crap this may actually be something. the two bolts are at the TOP of the two intake ports on each head on the first two cylinders.....
I'm going to loosen everything on it and re-torque the intake and only go hand tight or 1/2 the torque on those two bolts!
I don't think that it's an intake leak causing a lean pop/backfire...
I am going to go through about 3 quarts of oil and remove the VC's and loosen all the rocker nuts until they clack then silence each one with ONLY enough movement to do just that. then that will leave absolutely no possibility of a valve hanging open causing this.. I still think it's not what's happening... I took the words zero lash and 1/4 turn very seriously when assembling this top end...
ANd after doing the intake and cleaning the plugs and running it again then re-reading them that I'll re-post the results... That' s a lot or "re's" but I've had a lot of coffee this morning
Well, here is something to look for after you rev it to WOT. If it pops back though the carb on engine deceleration, the vacuum leak somewhere would make sense since your engine vacuum goes up if you romp it, then take your foot of the gas. The extra vacuum will pull oil into those two cylinders, lean out the mix on engine deceleration and pow. If it pops back though the carb on rev-up, or aceleration to WOT, then it probably isnt a leak; using the same logic your vacuum leak will become less since the engine is pulling less vacuum the faster it revs.
This engine pops AND OR hesitates when you go from idle to WOT. If you're moving a bit and go WOT the pop and or hesitation is much less pronounced at times, but sometimes just the same...
He had this problem before he brought me the engine to do the head gaskets. I've even put on a diffrent holley carb, the model he used was a 3310 the one I had was an 1850 or some weird # like that...
The problem remains. and like Ross say's I think it's in 1, 2 and 3 also.
Are you sure you got the plug numbering correctly? Just looking at the way you numbered them vs. the way they are laid out on the cardboard, doesn't make any sense to me, lol. Just to make sure we're on the same page, 1,2,3,4 are all on the passenger side, 1 closest to the front, and 5,6,7,8 are all on the driver's side, 5 closest to the front. The reason I ask is, you have 3 (maybe 3.5 or 4) dark plugs and the others are decent. On a dual-plane intake, one half of the carb feeds 1,4,6,7, and the other half feeds 2,3,5,8... so a carb that is running bad on one side will only affect those four cylinders.
If you DO have them numbered correctly (you probably do), then I'm starting to think that Ross's ignition/plug wire theory might be more on target, since those are all neighboring cylinders.
Regardless, if I remember right, your original problem involved the idle screws being 'un-responsive', which usually means you have too much fuel dumping in at idle for whatever reason (warped metering block, plugged air bleed, mis-adjusted throttle blades, too much T-slot, etc...), and even if you DO have an ignition problem, you'll still be back to the carb idle problem after the ignition problem is fixed.
This is a Chevy 396 bored +.060, with an Edelbrock Air Gap RPM Open Plenum Air Gap Intake. In a 79 Chevt truck.
The right 4 are 2 4 6 8 and the left 4 are 1 3 5 7 as we look from the grill.
The box they were in was 1 3 5 7 in front and 2 4 6 8 in the back row and that's the way I took the pics, maybe I got the pics out of order, or whatever...
The pass front 2 cyl's and the drivers 1st cyl, are black and wet...
OK, I've got the truck and before I ohmed it I checked the intake for leaks (again) on top, then inside the valley by plugging one VC then shooting carb cleaner into the other and plugging it.
The results are nil, the engine creates pressure in the VC's when you plug them so I'm sure the rings are crap in some of the cylinders... The crosshatching was almost invisible when I had the heads off, but the engine was superbly clean with NO sludge or junk anywhere and you could almost believe that it's only a 12K motor.
Anyhow... So I know it's not an intake leak.
Here are the results of the temperatures on the hedders.
a distance thing? I mean, the plugs with the longest wires, farthest from the distributor are the darkest. I dont have any experience with a coil going south, but could it manifest itself like this? Just a guess......
I removed the rotor to see why I was only getting about 5* of advance...
The counter weights were screwed up, the springs were too light for my tastes and one of the counter weights was at a goofy angle on the shaft...
So I grabbed a shebby 350 Dist I had laying around off a Monte, and took the weights and springs off it, I am getting ready to fire it up in a minute...
the other 30% I think is that when I took off the damn cap and looked at teh carbon transfer tip the damn thing was RETRACTED into the cap... The idiot who put it together places it ON TOP of the rubber grommet instead of UNDER it, and the spark had to JUMP to the Rotor pickup then JUMP to the friggin Distributor Pips, THEN jump at the plug, and that takes a lot of piss out of a spark...
It looks like You two who said "Electrical" issues are going to be my new heroes... We'll see.
OK, here's what went down... I repaired the dist advance. My springs are better than the originals but I only get abotu 6* mechanical advance overall and it's all in at about 900 to 1,000 rpm.
Once again the damn carb is pulling vacuum at idle to the vacuum advance. I thought I cured it with the second carb but I did not.
So, I opened the secondaries enough to close the primaries enough to have zero vacuum at the damn vacuum advance nipple, and then the fukin AF screws don't effect the idle at all.
There is no goddamn happy medium with this fukin pair of carbs on this damn chebby...
The throttle responce was incredible witho NO load but has a big BOG and sometimes a Bog and Backfire with a load on it.
I'm pissed!
He's buying a cheap azz edelbrock 600 soon and we're going to try that! I didn't replace the wires yet because I fixed the cap and advance (Will be getting new stronger springs or lighter weights tomorrow) The wires aren't bad enough to warant the full monte of this hesitation and pop, and the wires he brought me are 10.8 MM ACCEL and he has only got 45 degree tips in the kit and he needs straight on tips, so they will come tomorrow.
I just HAVE TO KNOW what's keeping this farkin carb from idling WITHOUT pulling full goddamn vacuum at the dist! ARRRRRGH!
Get the advance problem fixed that should get a lot of the bog fixed.Have you tried setting the timing with a vacuum gauge?
When you have the electrical in order the Idle screws are an easy fix.
The biggest issue with the carb is that I CANNOT adjust the secondaries with the carb on the truck because I need to use VICEGRIPS on the screw head to get the sunofabitch to move... Open OR close, although I can reach it with the screwdriver it's too farkin stiff.
I used a vacuum gauge on the farkin advance nipple so I could see when the vacuum was zero when setting the idle. That's what alerted me to the bad mech. system. The new one in (even thoug it's weak too) caused me to advance it another 12* to get it back to 10* BTC (which is the best running position for the moment. Which is good, and caused me to get a whole new set of rules ready for the damn carb that's pissing me off...
What is wrong with my tuning of the carb or the carb it's self or the engine, when the damn thing will NOT idle without the secondaries well into the transition slots....
That's the ONLY way the engine will idle WITHOUT drawing vacuum on the distributor...
This should NOT be happening to a totally separate carburetor.
I am pissed, and now I'm not thinking clearly.
I need BOURBON! (but I'll wait until at least noon )
Maybe it's a Southern car - try pouring pour some of the bourbon right down the primaries -
I mentioned this earlier, but have you tried either plugging the vacuum advance off, or running it off the manifold vac? Kind of seems like your fighting a timing curve issue along with everything else. Just a thought. I always try to change one thing, see if it makes a difference, then change it back, try something else, change it back, etc so you can sort of isolate variables if that makes sense.
If I plug the vacuum I only get 6* of timing. And that's all in by 1,000 rpm's because it needs lighter counterweights I'm sure...
With the vacuum hooked up, if I get the carb to run where the AF mixture screws will kill the engine when screwed in, the gawddamn vacuum advance is running 24* or so. This damn carb or this damn engine won't let the carb be adjusted to run without constant vacuum to the vacuum advance nipple.
That's why I needed the secondaries open a tad, but when I do that the TS are overexposed adn the AF screws will not do anything to the motor....
Good call on the Chevy engine/firing order... I shoulda just figured that out on my own lol.
If the vacuum advance is causing you so much headache, just unplug it until you get the damn thing running close to right! A few thoughts on the distributor:
1. On every distributor I've ever seen, the vacuum advance mechanism is COMPLETELY separate from the mechanical advance... meaning it can pull in 25 degrees of mechanical advance, and in addition to that, 10-15 degrees of vacuum advance... so added to the base timing of say 10 degrees, you can have as much as 50 degrees of advance when everything is in full. The vacuum advance pulling in should have zero affect on the mechanical advance rate.
2. The mechanical advance mechanism should be able to pull in an additional 20-25 degrees of timing, meaning if you set the base timing at 10, plug the vacuum advance, and rev it to 4000rpm you should see about 35 degrees of advance. Time the engine for a certain max advance (around 35), NOT for initial advance, and it will probably run a lot better. If you are only getting 6 degrees of mechanical advance at 3000-4000rpm, then that needs to be fixed before anything else. Either run it with 30 degrees initial timing (bad idea) or change the limits of the mechanical advance to allow for more advance.
3. The AMOUNT of mechanical advance is not affected by the springs or the weights, it's limited by some stop that limits the travel of the weights. This is what you need to focus on first, to get the right amount of mechanical advance in the distributor. Once that is set up so you can get 10 degrees inital and 35 total, then you can mess with the springs and weights to get it to hit max advance right at about 3000rpm.
And yes, your idle problem is definitely an issue, but I would fix the advance curve first and get the base timing set right, then get the carb to idle right so that the rear blade does not expose the rear T-slot and the idle mix screws are responsive, and see how much front T-slot is exposed (should be less than .040") and LAST connect the vacuum advance.
Just out of curiosity, can you adjust the idle speed to where you just barely start to see vacuum on the vacuum advance port, then pull the carb and look to see how much T-slot is exposed at that throttle position?
OK, I almost read everything you typed but I stopped...
1: I definitely need to replace the counter-weights on the mech adv. but the damn engine will NOT run wituout vacuum to the funkin nipple, and, that is more important than bad advance springs for the moment, because, at idle the mechanical advance is nil, and the timing holds perfectly steady.
With the vacuum advance OFF, the engine will run, but my vacuum gauge say's to me that the nipple it is attached to is puling vacuum. (nipple at the carb where the advance get's its vacuum) Therefore the carb is NOT adjusted correctly in my opinion because there needs to be ZERO vacuum at the distributor, or the damn advace will not work since it will already be ON as soon as the engine is started.
So, I have an engine that will run 8* BTC steadily, and will run beautifully well, but the damn AF mixture screws can be all the way OUT or all the way IN without efecting the idle. This, to me, means I am running too much secondary air and fuel...
BUT, when I close the secondaries, no matter where I have the AF screws the damn vacuum to the distributor is on, and this is what I cannot stop...
So, can someone tell me how to get a motor to run great with full vac adv at idle? Should I rely only on mechanical advance for this guy and just loose the vac? That will cause a bigger hesitation and pop at WOT won't it?
Unhook the advance and set the darn initial timing to 10-12, that will allow you to close the primaries.
Then leave the advance unhooked and tune the darn car.
Your weights arent too heavy I promise, the weights dont limit total as said above. The springs control rate and the pin/bushing controls amount, completely seperate from the vac advance
It sounds to me like you have the initial timing too far retarded due to the vacuum advance pulling in at idle, that fact alone it would explain every symptom you have, except for the crappy looking plugs
It funkin idles stupendous with the vacuum DISCONNECTED...
8* is great 10* is where its at now and it's pretty much optimal, with EVERYTHING disconnected. ()NO fluctuation on the timing at all)
The gaddam carb will NOT run the engine on the primaries alone WITHOUT pulling vacuum.
There is no sweet spot for this motor where the secondaries and primaries are at a point they will run the engine and the vacuum to the distributor is zero. I read it on my gauge with the vacuum DISCONNECTED in every possible positioning of the pri's and 2nd's.
So, I need too much secondaries to run the engine with the primaries closed enough to get zero vacuum to the damn nipple on the carb.
When the secondaries are open enough to get zero vacuum in the advance nipple there is too much pull on the transition circuts and the Air Fuel Mixture screws do nothing.
So my observation is: This carb cannot drive this motor without vacuum pulling on the distributor if I want to be able to have teh AF circuts working enough to close them off and be able to kill the motor. (which allows me to adjust the idle mixtures for richer or leaner idle)
I bought a new timing curve kit for it and will go with the strongest setting to prevent any damn advance from happening until the last possible moment.
But I know that the initial timing is not the issue just yet.
Yesterday when I replaced the mech. springs and wings, I was able to get a perfect 8*-10* idle with no fluctuation, with the Vac Disconnected and my gauge on the nipple reading it.
The carb simply will not adjust to a point where the damn nipple does not have vacuum pulling on it.
This is the ONLY orifice on the carb with wich to pull vacuum for the dist. And I can't get the POS to work...
With the timing at 8-10* I can and ahave adjusted the berjeezus out of the friggin secondaries and primaries, but there's just no place that the dist. nipple gets zero vacuum at idle unless the secondaries are grossly misadjusted.
So, it's diffrent carb time, or, it's use Mechanical advance only and constantly run Distributor advance...
Why is 8*-10* perfect, give the poor thing as much initial as it wants. Maybe he didnt degree the cam, maybe its not the correct cam, who knows, but turn it up to 15 and see what it does.
I run 14 initial in my Mustang and would run more if it would start with more
OK, I don't see what initial timing has to do with the butterflies on the carb being closed enough to stop vacuum from pulling on the dist.
Or should this damn engine be pullling full favuum to the dist all the time. It don't make sense to have full the vacuum pulling on the dist const5antly. THat makes the vacuum advance null and void to a point.
drop me a # I can call you at or just call me so you can beat the facts into my head, adn I can 'splain myself better... 707-416-7215 (Verizon)
Are you sure the timing light is on the #1 plug wire, and not on the #2 plug wire?
Its been a long time since I worked on a chevy but I thought the #1 plug was on the left(driver) side front on a chevy?
There's an old Oldsmobile that has the #1 that's not the farthest foreward, but I got mine on the right plug
I spoke with Gary (Iron Age) and Ross this evening and I finally have my head wrapped around the timing aspect. I am going to make some adjustments in the morning, I will install the new timing springs, then loosen the intake valves on 1 3 and 2, then I think we will be on the money with this damn truck! We'll see, it's going to take me about 1/2 the day
OK guy's Credit goes to me for puting ou tthe labor, but mostly to Iron Age and MY427, for some tech support. That Gary really knows his carbs!
After drilling a 5/64" hole in each butterfly of the carb, I was able to close the secondaries engouh to stop oulling fuel with the air I needed.
I then, could close the primaries enough that them sunofabitches finally stopped pulling vacuum on the distributor advance module. (not that it was hooked up, but the nipple kept getting vacuum at idle)
Once that was solved, I started and warmed up the truck Then I timed it by my vacuum gauge adn ended up with an initial timing in the area of 18* BTC, with a total way out there under the WP where I couldn't read it and my old analog light did nothing to help and there was no timing tape on it... never mind.
Anyway, after pulling the plugs again for another reading I found the threads once again slightly coated with oil on a couple and a somewhat modest amount on a couple others and then I had a revelation!
Like a quiz, let's see who's quick enough to tell me the biggest problem with this spark plug pictured below?
