I just finished putting a 454 engine in my '78 camaro. When I put my feet on the gas the car starts with backfiring a couple of times before it takes of, it also doesn't produce the horsepower I expected from this setup. The exhaust metering system shows a rich combustion fuel to air ratio threwout the whole rpm range. Does any one have a idear??

If you have a Holley carb you might have blown the power valve. If this happened it will dump raw fuel and cause it to run rich. I would invest in one of the books which disects Holleys and gives tuning advice. Good luck.

Steve R.

put a timing light on it, if it's ok you may want to try adjusting your valves,(rocker arms). If either one of these were out they could have easly blown your power valve also.

thanks steve R and Scotty dog for your quick reply. The engine has a 750 cfm Edelbrock carb. I checked the timing it was almost 10 degree advance, I also readjusted the rocker arms two times, no change. I measured the pressure in each cylinder this also didn't indicate any problem there. What is the power valve in the carb exactly. Does back firing automatically mean that one (or more) intake valve(s) is (are) not closing completely, or can the fire be triggered by something else than the fire in the cylinder during combustion?? (in other words can a back fire excist when all the valves are closing correctly).

Greetings Bart

Power valves are not an issue with Edelbrock carbs. Try a compression check. Have you turned your motor over to see if all the valves are opening, and the rockers are moving. Good luck.

Steve R.

Hey bart. I know this is simple but is a common mistake. reCheck your firing order.


71 Camairo

is there a chance you have a vaccum leak somewhere ? you can check this by spraying wd-40 around area's that might suck in air, and if you idle changes, you found your leak.
just trying to narrow down the problem.
good luck,
bruce