i have a crate 454 generation 6 engine in a 69 chevelle. it has been backfiring. i checked the header tube temperatures they are all running between 600-700 degree except for number 2 cylinder is running about 160. i am getting spark to the plug. i changed the spark plug, plug wire, distributor, cap, rotor, carb and timing. i checked for a bent push rod, it not bent and every thing looks good under the valve cover. i took a compression test on three cylinders 2,6 &7, they were all a round 165 psi. any suggestions? timing chain, cam or lifter?

Not timing chain. Check your valves, lifters, cam lobes for that cylinder. I would check the plug and wire once again to be certain. I know you changed 'em, but uninstall that plug, lay it on the head and check that it sparks just to be sure.

thanks, i will check for spark at the plug again. can i pull the valve cover off and check lifters, cam and valves while the car is running?

yes, but you'll get oil everywhere. I would probably start with the engine off and see what I could eyeball. Who know, it may be as simple as a racker backed off or a pressed-in stud coming out.

I finally got around to checking the valve train, the plug and for spark again. Everything looks good and checks out OK. I have the valve cover off and everything is tight and seems to be working with the car running. The guy that has been helping me check things out said if the compression is good that there should not be a issue with the valve train? I'm going to pull the intake off next. Any other suggestions?

Make SURE the exhaust valve on that cylinder is opening. If its not, you will still get a compession reading but it will backfire out the intake bigtime when running.

possible exhaust valve issue on that cylinder. But when a exhaust valve doesnt open its pretty evident by popping big time up thru the intake (nowhere else for the pressure to go) Swap plugs and wires for 23 cyluinders and see if it changes places. Also a rotor/cap can crossfire too. good luck. Paul

I have the intake and valve cover off. How can I check the to see if exhaust valve is working?

did i read that right? :wacko:

Hi again,
I work a swing shift so I only get back to this site once or twice a week. I don't know to much about the mechanics of a engine. I am trying to find out how to check if the exhaust valve is working or not? With the engine running and valve cover off, all the valves, rocker and push rods seem to be working find.
When I point the heat senor gun at the headers I get 600-700 degree on all but number 2 cylinder it runs about 160. I have double checked everything. Spark plugs, plug wires, cap, rotor, distributor, intake and carb. I have the valve covers and intake off now. I am trying find out if I can check the exhaust valve without having to pull the head off? And if I do have to pull the head off will I be able to tell then?

You just need to have the valve cover off. Watch the rockers for the number two cylinder and rotate the engine, if both rockers go up and down fully, the valves are opening and closing. Now that you have the intake off, you could rotate the engine and watch that all the lifters are coming up and going back down, but if you rotate the engine you will lose the spot that your distributor drops back in at.

Truthfully, their is little point in having taken your intake off for this problem short of having a wiped out cam lobe.

Jeff

Thanks, I will check it out on Monday. I pulled the intake off to make sure there was a clear path from the carb to the intake valve. The cylinder was getting spark, I wanted to make sure it was getting air and fuel.