Could be the loose nut behind the steering wheel.

 

afraid its a bit more complicated then that man. We checked the timing with his light. I had it set at 4 degrees advanced at idle. He turned it up to 8 degrees advanced at idle also with no effect still popping. He even went higher then that and it was still popping through the carberator. The way i see it, it could only be the cam or a stuck closed or open, or not enough of either causing excess run off gas to burn up on the piston when its not supposed to.

Remember this only happens on heavy throttle and the secondaries being opened. I read that when the cams start going out as the journal begins to flatten this causes the valves to not want to open enough or close causing the pistons to fire at incorrect times. I just have to think now should i rebuild this motor, the suburban motor ive had out in the barn for 2 years, or the 355 in my other camaro or just go out and get a crate motor. the one guy was right, these cars really are projects regardless of body etc.

 

The valves may not open enough from lobes going flat, but the cam wont stop them from closing all the way, no matter how worn the lobes are. If you took the cam completely out it would just leave all the valves closed.
What can cause the valves to not close all the way are sticky valves. If your valves are sticking or bad, then you might get the backfiring you're getting. Replacing a cam because of sticky valves is not the answer. Somebody is leading you astray.
The first thing I would do is get a can of spray carb cleaner and spray it down the carb with the engine running at a high rpm, around 2500 or so. Keep spraying it until the engine sounds like it is dying. Stop until it picks up, and repeat this until you use the whole can of carb spray. This will often unstick valves if they are good, but just sticky build up from additives and carbon.
If it doesn't change anything, the valves may be in need of attention, but I still don't buy that the cam is doing this. Might even be a bad timing chain, but not the cam.

 

thanks for the advice, i am going out of town fishing for 3 days when i get back though ill try that idea out to see if it does anything. you do make one point i like though about sticky valves considering i did find a bit of residue of antifreeze remember from the intake job in the valve covers could very well be stickyness. yes i did change the oil out though. I dont know a whole great deal about timing chains though, have to see when i get back.

 

Anti freeze under the valve covers has nothing to do with it. The stem of the valve most likely has carbon, burned oil, or varnish on it. On the other side of the valve seal. If antifreeze got past the seals that easily I would say the seals are shot. Do as Val says, its a new trick to me, I have always added fuel injector cleaner to the gas and prayed.

 

When I worked for the local Cadillac dealer in my youth, the mechanics used to do that trick to unstick valves. It makes a huge cloud of white smoke and stinks like burning carb cleaner, but over half the time it works.
Some of the tuneup guys swore by it and did it as an annual thing for regular customers.

 

ill do that tomarrow. Should i add the fuel injector cleaner in there too like as in puting it down the carb? or in the gas tank

 

I thought your car was carbed? Injector cleaner would clean things up if the carb is gummed up, but didn't you just replace that???

 

I use injector cleaner in the gas tank. No matter what the name on the bottle, I'd bet its all just Zylene inside. Injector cleaner, carb cleaner, fuel additive, or whatever.

 

I do too Damon, but no reason to if it's a new carb.