Maybe someone can point me in the right direction here. My car started missing a while back. By pulling spark wires from the dist. cap I determined that the culprit is #8. I checked compression (about 150 -- just like new), tried three different spark plugs (Bosch Platinum), put air pressure in the spark plug hole and verified that I get air flow out the exhaust and back through the intake when I rotate the piston through its cycles. I even pulled the valve cover to make sure the valves are working properly, and adjusted the lash on that cylinder per the directions in the book. I checked the temperature of the exhaust manifold using a thermocouple and found that the temperature of the #8 manifold is about 100 degrees F cooler than the ones next to it.

I still get no difference in the engine running when I pull that wire, even after pulling a couple of others off. I get a drop in idle whenever I pull off one of the other seven plug wires. I even pulled off the fuel injection system and put the old quadrajet back on to see if it would help. Can't hardly even spin the tires in second with only 7 pistons working :(

Anyone got any other places to check? I am thinking the next thing to do is pull the intake manifold and look for a torn gasket.

That would give me a good opportunity to put in a new cam but I would rather wait till winter to do that and drive it now.

 

Where's the part about you changed the plug wire? Or you changed the distrubitor cap?
You do need for the cam to open the valves a bit more than just enough to pass air. Did you check for full travel at the rocker?
Good luck with it.

 

yup, could be a flat cam lobe.

 

I'd replace the wire, cap, and rotor before I tried anything else. Wait for a REALLY dark night and start your car, if you see sparks arcing from the wire you've found your culprit.

The worn cam lobe I had on my 383 in my Camaro was so bad the rocker was hardly moving.

I went through 3 cams before I figured out the yutz that assembled my heads had shimmed the spring so high on the # 7 intake valve spring that I had coil bind with stock corvette springs. Apparently he used *USED* springs. He had retired by the time I found out, I was going to go rip his head off. I paid him for new ones, oh well.

In any case, start with the small stuff, I wouldn't start pulling the engine apart until you've replaced the wires, checked the spark plug gap and checked the cap and rotor.

 

I just noticed you have FI. Is it TBI or EFI? If it's EFI did you check the fuel injector?

--
Steve

 

If you had a flat cam lobe the lifter would start to rattle with the increased clearance.
Norval

 

Thanks for all the posts. The first thing I did when I had the miss was replace all the plugs, the wires, and the cap and rotor. So I covered those already. When I had the valve cover off, I didn't measure the actual travel -- I guess I should -- but it "looked" like they were moving about the same as thee others. I do have a dial indicator so that is one thing I can try. It is possible that a wire has gone bad. I looked in the dark and did not see any sparks, and when I hook up a spark plug externally it does spark. Also, the exhaust manifold does heat up, just not as hot as the other cylinders so it is sparking at least some or most of the time.

 

So what about the Fuel Injection? Tell us about it.

--
Steve

 

What does the spark plug look like. I would guess a blown head gasket but the compression test being good is strange.

 

First, the spark plug gets kind of sooty looking, I presume because it is either not burning appropriately or because it only fires some of the time. I am planning to hook a scope on soon and see how reliably it is firing.

Fuel injection. I had the Holley projection-2. It is a 2 barrell system, with about 670CFM. It worked great, but seemed kind of flakey so I pulled it off and put the carburetor on. I am planning on putting in a projection-4 system that I bought off Ebay when I get the car running right on the carburetor.

The projection systems are TBI units, a rather simple analog system.

 

hmm... If you've got spark and good compression then I guess it would either have to be a bad intake gasket, assuming your valves are traveling their full distance. Have you tried the old trick of spraying WD-40 by the gasket with the engine running to see if the RPMs change?

--
Steve

 

Just a thought, but do you have the pcv hose hooked up to the vacuum "T" which goes into the the #8 intake runner instead of the rear of the carb?

Chuck

 

Negative on the PCV valve. I am going to give it a shot of brake cleaner or starting fluid and see if there is a leak on the top side of the gasket. It could also be leaking on the bottom side.

I took the car out for a run today, and after adjusting the valve yesterday, it does run a bit better. Perhaps my cam is getting a flat spot. Boy, I would hate to have to put in a new high performance cam ;)

I will drive it for a while longer, and check a few more things, but I think I am getting down to the short list of things that it can be -- wire, intake gasket, or cam.

Thanks for all the help.

 

A flattened intake cam lobe will usually cause a popoing sound in the intake manifold.