Probably not your problem,but the marks on the crank dampner(pulley) have been known to be noticeably "off" as in MISMARKED. Have you checked or verified pulley is properly marked and degrees are entirely accurate?
KS, is it possible you have a mismatch between your crank damper and your timing pointer. This can happen with an engine assembled from a pile of parts. If the builder set the timing by ear when he was breaking the engine in, he might not have used a light on it and didn't notice the mismatch. edit; Flatheadjohn47 posted while I was typing. LOL
I would start by getting it timed right. An adjustable timing light works great for this. It gives you the ability to make sure your distributor is working as it should. Running your vacuum off the wrong port will give you bad results.
"squirrel" has a good point about your cranking compression, rule of thumb is anything over 200psi puts you in at least premium fuel territory, with iron heads, and you mentioned you had iron 882's and the block was decked, do you know if the heads were milled? There are engines that will run on pumpgas with that kind of cranking compression but usually they are aluminum headed. Camshaft duration can make a difference with cranking compression and the type of fuel needed for a particular engine also. Your idea of thicker head gaskets to get the cranking compression down might be a option, try to get it running right first with premium fuel and see what it does, the detonation is probably a combo of both fuel octane needed for your compression ratio and oil contamination. You'll get it figured out. Posted using the Full Custom H.A.M.B. App!
When it was brand new, I set the timing to 4 degrees (stock 400 spec) and it ran very good with no knocking. As for timing it today, the balancer is new and not spun. The distributor housing is marked with a matching mark on the intake, so I know when I am close. I used a GM timing cover off a 400 with a timing tab that matched the timing tab on the chrome cover I replaced. Same location that I used when I timed it early on when it ran good.
To my knowledge, the heads are not decked. As I said, it is not supposed to be a high compression engine, but the numbers seem to say otherwise. Also , my compression gauge is very old so it could be off too. As for the cam, it is not very big, so I am not bleeding off any compression. I did run on premium gas early on. I cleaned up the stock steel valve covers tonight and will try them tomorrow. I am tempted to pull the carb off and look down the intake to see if it is oily inside the runners. I also thought that after I swap covers, I might put a clear hose on the PCV valve to see if oil is still getting sucked in. New plugs too.
I had one do this and it was the cam/ lifters... The cam was broken in correctly but had a flaw in the machining and lost 4 lobes more or less... They sent me a free cam and lifter set to replace it... I paid a little extra and upgraded to a roller... Cam break in is very important though...
If memory serves me, the engine had the piston down in the hole about .025 and used a .015 head gasket from the factory. The machinist zero decked the block and installed .041 head gaskets (or .039). That made the quench right. CR with the dished pistons was about 9.4, so how the heck is it reading over 200 on the pressure gauge? I should only be reading about 140 psi. (9.5 x 14.7) I did not open the carb when I cranked it, was I supposed to do that?
Over 200 psi isnt 9.4 ratio. Either your gauge is wrong or something isnt what they said it is. Im also wondering what your running for a cam that requires a dual spring? Maybe I misread but I thought this was a mild stock type build?
Just chiming in, I know you are getting a lot of advice, a lot of it good. Here's where I would start. 1. New plugs or at least pull and clean the ones now. They are probably ok for troubleshooting if you clean them. 2. Disconnect and plug the PCV vacuum port. 3. Disconnect vacuum advance and plug that port too. 4. Set timing manually and then dial it in. Drive it like that for a while and see how it runs. If it's fine... 5. Use a vacuum gauge and plug vacuum advance into a venturi port. Low vac at idle and steadily higher with rpm. 6. Figure out the baffle thing with PCV. I also agree that your pressure seems very high. But get that other stuff figured out step by step. Should be able to dial it in in a few hours. Good luck
I have not read every post on this this thread but. Here is what happened to me m/t valve covers on a sbc would use no oil running around town but on the highway it would use a shitload tried everything bottom line valve covers had no baffle . hole for Pcv was directly pushrods and at highway speed would push oil right to the line suck it down intake cause detonation smoking running like crap Posted using the Full Custom H.A.M.B. App!
Update - Added 1/4 turn to lifters (now at 1/2 turn) New stock valve covers with baffles installed. Dual PCV valves plumbed Breather in one valve cover. New spark plugs R43T (old were R43TS) gapped at .045. The new plugs have the electrode up inside the plug. (should help with detonation issues - as per engine builder) Added 5 gallons of 91 octane to tank with 5 gallons of 87 octane in it. Borrowed an adjustable timing light...not sure how to set the timing with it. Bought an adjustable distributer vacuum advance. I set timing by my distributor to manifold mark, and took it for a test drive and it ran a bit better, but had bad dead spot when I stomped on it. I am not going to rule out a flat cam yet. It seems like I can hear very, very light lifter ticking. Could be header ticks, or just valve train noise. First things first...total timing. Engine builder said 32 -34 degrees, and maybe with the vacuum advance connected. SO how do I set the total timing???
Pretty easy, disconnect the vacuum. The timing light will have a dial or digital readout and buttons, the basic idea is that you run the engine at whatever rpm you want to set the timing at (say 3000 for total timing), then set the knob or display for the advance you want (say 34 degrees), then adjust the distributor so the flash on the timing marks are at ZERO degrees. The light delays the strobe by the number of degrees you set it to.
First learn how to use the timing light! Run the engine up to what ever RPM is past full advance, then adjust the timing light to TDC and read the degrees of advance on the light.
Easy easy easy check for bad cam lobe. Wipe off the push rods, With a paint stick, mark a line parallel with pushrod. Start it, the push rod should spin and the paint line lets you see it spinning. No spin = cam wear problems. Takes 30 mins to do and confirms or denies a cam break in problem. This works very early in the onset of symptoms, so it really save anguish and tail chasing. If you could visually see a rocker not moving as much as the others, you'd have had this problem for quite a while, quite a few bothersome and obvious symptoms and plenty of other crap telling you something is wrong. Also, until you've verified the timing marks with a piston stop test, you have no idea what the timing is actually at. Might as well be pissing up a rope
I might do the paint stick trick. But I want to make sure the timing is close before messing around too much. I want to install the adjustable vacuum can and set it for 8-12 degrees of advance. Not sure how to do this except to install it and read the difference in timing on the timing gun with it unplugged and then plugged in. Second, since it is the factory tab on the timing cover, I will "assume" the mark is zero, and set total mechanical timing for 32 degrees with the vacuum disconnected. How do I verify the zero mark...run a stop bolt in the #1 hole and rotate both ways to find center? Is there an easy/good/safe way to de-carbon the cylinders? Sea foam, water-rubbing alcohol down intake of running engine, something else...? I have a feeling the cylinders are caked with the same oil crap that was on the plugs.
Ok, took a bit to separate your issues from the first post. There's no way the engine came from the builder with 200 plus cranking compression. Especially with dished pistons. There is a correlation with dynamic Compression Ratio and cranking compression, it's not exact but with knowing the INtake closing, the leakage and static you can calculate cranking. I just checked a advertised 7.5:1 statics cr cranking compression and it was 140. In my records I have a 9:1 advertised measured at 150s average but it was worn. I also recently did a 10.4:1 and it's cranking was 175 but brand new. So if you'd follow that relationship 200 plus has to be WAY Over 10:1 and probably closer to 13 or 14 to 1. Seems impossible right? Ask your builder what you should see ass far as cranking compression. Another way to increase compression is to put a smaller cam in it altering the IC point and building more cylinder pressure. Like an RV or towing cam. Small cams don't usually break valve springs though. Another way to increase cylinder pressure is to play with cam timing and altering the intake closing event closer to BDC. Another way is for great gobs of build up in the cylinders. So to sum this up, 200 psi plus is a red flag unless he built you a race motor for your truck. Some simple diagnostics should get you headed in the right direction.
Water slowly down the carb of a warm engine will safely get the carbon out. Sea foam in a vacuum port will do it too. Just follow the directions on the can
I am going to check to see if the pushrods spin tomorrow. I am starting to suspect that the cam might be going flat or I have cheap lifters. I hear ticks now and then. I also looked at my stock vacuum advance and it is a 15 degree unit. I want to replace it with a 12 degree unit, but I need a good reliable vacuum number to work with first.
I'd give this a giant BINGO! I have had the same problem with my Plymouth and came up with the same results you have here because of this issue. The other thing to be aware of is get that vacuum advance on the correct port. You are looking for ported vacuum, not manifold vacuum. Basically, Manifold vacuum is present at idle and diminishes as the rpms rise, where as ported vacuum stars from idle with a very weak signal and rises as the Rpms rise. Basically, the way you have things set up right now, you have your initial vacuum at idle, plus whatever the total extent is of the vacuum advance too. At some point as the engine RPMs rise, the vacuum advance is losing it's signal as the mechanical is advancing... In the mid range you'll have way too much advance going in.
As long as one knows what they what to accomplish, how to do that, and what parts they have and how to use them there shouldn't be. Is that too much to ask from gear heads
I ordered a Crane advance limiter Plate and will return my adjustable "made in Taiwan" vacuum advance and buy a AR12 (VC-1838) from Napa. That should allow me to limit my advance to 12 degrees. My vacuum was 15#
When I drove it today, it seemed better but, when I hit the gas hard, the truck just seemed to die. My vacuum advance was connected to full manifold vacuum. When I hit the gas, the vacuum instantly fell off and the advance was gone. How/what is supposed to counter this from happening?
uh...it's supposed to work like that. The engine can't use all that advance when it's under load, making power. Although if the base timing is too far retarded, the engine won't run right. You kind of need to get it set up to where the timing is right under all circumstances. It's not easy
Seems like the OP's suspicion of high crankcase pressure would be counter to the leaking intake gasket theory assuming they were leaking on the inside.
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