Carb Backfiring FRUSTRATED

[Jin2116]

I recently bought a 1976 corvette off my uncle, the car has been running great up until last weekend. I was racing a Z/28 on the highway engine was running great i pulled over talked to guy. got back in the car went to to take off and it started backfiring out the carb when i stepped on it. only seemed to happen if i opened up the secondaries. Drove it home took off the valve covers found a loose rocker arm on #1 cylinder intake valve, and a bent pushrod on cylinder #1 exhaust valve. I have replaced the pushrod, checked the rocker arm, reset ALL the rocker arms on the entire engine using proper procedure After inspecting and checking every rocker arm and pushrod to make sure the damage was confined to one cylinder. with everything re assembled I started the engine, seems to idle fine, touched the throttle nothing everything is fine, trip the secondaries and she backfires again.

Now i check the timing , It couldn't be better. I slowed down the idle and pulled each wire off individually to make sure they where all firing. they are all firing.

My uncle is a Certified mechanic and he is fairly stumped on this as well, we have ruled out a bad cam because the cam has 1000 miles on it and was broken in properly along with the rest of the engine. If anyone has any ideas please throw them my way. I appreciate it and thank you.

[maxwedge]

I'd do a leak down test on that cylinder, not a compression test, then if ok I would look for a broken valve spring. This all assumes you are sure the cam exhaust lobe is good.

[16th hippy]

have to second on Max's post....sounds as if a base engine problem(mechanical). Please keep us posted though!

[Jin2116]

Alright well the problem was #1 exhaust valve wasn't opening. The cause of that was that the rocker arms where not compatible with the valves and kept on kicking off to the side. thus wearing a groove into the arm stud causing the rocker to bind. Thus bending pushrod. The head needed to be removed the exhaust valve replaced because the wobbly rocker wore through the hardened tip on the valve and if it dropped i would be out an engine. the studs needed replacing as well. new self aligning rockers installed. I would have done the work myself but i just had re constructive ligament surgery in my right wrist so im gimped. I did the diagnosis and all work involved up to determining the head had to come off. With one hand was a bitch. Thank you to bolth maxwedge and 16th hippy for your input. i appreciate it.

moral of the story use self aligning stamped or roller rockers on gm 350 crate engine heads, save much pain.