when I first started the motor to break it in, there was a good backfire with fire ball. and today when I started it to test for vacuum, I had the air cleaner off and there was another backfire but not as big. seem fairly normal but could be due to an intake valve I'm guessing. I think I am going to pull the intake and the head off to inspect all lifters and valves. what should I look for or will it be obvious if something is wrong.
I would think it didn't burn the valve yet but I would look for that valve to be wet and black.if you don't see anything obvious then place head level with combustion chamber up and fill it with a thin fluid. I use wd40. Then see if it leaks past a valve. I'm thinking it will do so quickly.
if this does happen what are my next options? Lap the valve again? new valve? I hope I wont have to get that seat machined...
Simple valve job if valves are good. Yes machine seats. Its not a big deal. The just run the right angle stone and grind it. But you may need valve guides. You should not need hardened seats. These cars have been run on unleaded gas for 40 years. It lasted this long. Why change.
Verify your firing order again. I haven't seen this posted anywhere. One weak cylinder won't cause this much lack of power. If this isn't the cause I would suspect cam timing next.....any chance you milled the heads, and now the push rods are too long, this another posibility. If it is a valve, it would have to be an intake valve. Just get the cylinder in question and put compressed air in it and listen for air leaking. At the carb to confirm a leaking valve.
Pulled the intake and valve covers tonight. Before I removed rockers, I noticed that where the pushrod meets the lifter was sunk down into the lifter. some pushed down an 1/8th, some 1/4, one maybe more. is this normal? they are hydraulic so I would assume so. the bottoms of the lifters looked just fine and so did the cam lobs that I could see. Could someone describe what a good lifter bottom should look like just to make sure?? Going to pull the head tomorrow and inspect valves/ seats.
Seems like a lot of preload and variation . you might need shorter pushrods or adjustable. Good lifter should be spiral pattern as lifter spins as its lifted. Should be flat not concave. I assume you have aluminum rockers? Are the ones that are in on lift of lobe at all?
The lifters are from Ta and they should be exactly the same size as stock. The springs are from Ta and they are also stock size. everything else is stock. Yes aluminum rockers. The pushrods should not be affected. I am not sure if they were on lift or not. The bottoms of the lifters are flat and have a spiral pattern. Would it be a bad idea to switch the lifters positions before I reassemble to see if that may change things.
I'm just trying to figure out what is wrong and what to do about the issue. I will not change lifter position.
It is very difficult to try and diagnose this over the net. It might help if we could hear the noise in a video. If you put a straight edge across the valve tips, they should all be even. I would try that. I would also get some adjustable push rods and and adjust each valve so you know lifter preload is right.
just put a straight edge across the valve tips. On the passenger side head (one that is making the noise) : every cylinder would have a valve line up against the edge and the other would be about a 32nd below, except for #6 (the cylinder that the noise went away from plug pulled while running) this valve was about a 16th under. On the drivers side head all valves lined up except for #1 cylinder had a valve about a 16th under but this side never mad any noise. inspected rocker shafts and all rockers seem to have the same amount of play. I see the grooves made by the aluminum but none stood out to be worse then others. they are very minimal.
Just pulled the head for inspection. I found a very small exhaust leak at #6. There was a small amount of carbon beneath the header and on the head where the exhaust was escaping. I'm sure this is what caused the ticking noise. Put water in all combustion chambers and none dripped out, so the valves are sealing good. The only other issue is the vacuum leak and loss of power. What could cause these aside from the cam being degreed wrong. I installed at 4degrees advanced which is what TA told me. I'm sure either way there should not be this much power loss. Could the vacuum leak cause the secondaries to not open enough for full power?
Water might not leak past a bad valve job. I've never tried really, but I was shown to use solvent, so... The tactic of using compressed air in the cylinder while the engine is together is probably more effective than a novice's eyes while apart. Too bad you didn't notice the exhaust manifold leak before removing the head. I'm not trying to sound like doom and gloom, but you're in a position now where you don't know any more than before and have lost a couple of diagnostic opportunities. I commend your motivation though! Re-try your test with wd-40 or something, it may leak a trace without much effect on running. After that, it might take a trip to the machine shop. Sorry you're having problems, good luck!
Yes water is too thick. You need a fine oil. WD 40 is good. Don't forget these are under pressure and an explosive combustion. Be 100 % sure. But you might have ticking noise solved . that's good. Secondarys are vacuum related if there isn't enough they won't open. Was car originally a 4 barrel car? If not it could be a cable problem. Could also be in tuning of carb. There are adjustments for secondary as well as changing rods and hangers. Did you jet up carb for headers and cam? That will lean out bottom end and so will ethanol added to fuel. These carbs never where designed with that in mind so jetting up is needed. The 212 should produce 15 in vacuum and be fairly steady. You said it fluctuates. So this is still something that needs to be diagnosed.
The car was originally a 2 barrel car. I did not know that the cables are any different. The carb is brand new. Ken at Everyday Performance rebuilt a quadrajet for me and supposedly tuned it for my application with the cam and headers. The fluctuation is about 1" of vacuum and seems to get less with increased RPM.
What is the difference? I used this cable last year when I had my Edelbrock on and it seemed to work fine.
It may not open the carburetor fully. You do have to check that. With the engine off, have someone floor the gas pedal while you move the air valves out of the way and make sure the secondary throttle blades are vertical.
