i have a 69 camaro 350 30 over, duel feed holley, a/t, when i stomp on it there is a big hesitation sometimes a carb backfire, it was dyno tuned, i have checked everyting and cant find the problem it has acam that is one step above stock v8 gives a little shake to the idle, i have pulled all the pushrods all nice and staight, good compression, distributor has petronix conversion, im about to replace the cam out of frustation, any other ideas

 

timing?

 

Pretty bad dyno tune if the car backfires and hesitates. As cplthomas said, set the timing properly, and if the engine still runs bad, take a god look at the carb set up. Jet size, power valves, accelerator pump, fuel pressure, etc.

 

I assume the car ran fine during the dyno tune. In that case the Cam would be pretty close to the last thing on my list to try. If you can drive the carI doubtthis issue is a internal mechanical problem.Two areasto watchwhen you accelerate. First is your accelerator pump needs to pushmore fuel into the engine. Due to in increase of air volume/fuel you need more spark to fire it.Since voltage will always follow the easiest path this is when your secondary ignition will most likely arc to some place other then where its suppose to go.

SO:
Check Accelerate pump,With the engine off look down inside your carb, work the throttle. You should see a nice stream. Don't do it more the twice or may flood your motor.While you have the cleaner off make sure the choke is fully open once the car is warm.

Primary ignitionis everything that it takes the fire the coil, secondary ignition is from the coil to the plugs. A weak coil,bad rotor cap, Distributer cap or tracking in the cap. The wires them selfs or a cracked plug could be the cause. If you are old school you know what a car sounds like when the condenser goes bad. Any car will sound like that with a weak spark.

There are many spark testers out there to stress your secondary ignition and see if it still fires. My favorite one is the OEMdelco ST125.

These are common issue there are more things that can cause this issue.

Just as a side note Petronics recommends you use full voltage to their modual. Camaro has a resistor wire required by point. Did you replace that wire?

 

Have you checked the gas level in the fuel bowls? Too low and you'll have a lean condition, too high and you'll flood out. Either way can give you an off the line bog. Pull the sight plugs one at a time while the engine is running and check it out, gas should just barely dribble out when set right. I put clear plugs on both my carbs, it makes it a lot easier to keep an eye on how it's behaving without making a gassy mess.
Almost forgot...before removing the sight plug, be sure to put a plastic or metal cup of some sort (spray can cap) below the sight hole to catch the gas.

 

I was having a similar problem with my '68 350. It has a Demon carb and the float level was too high. I lowered the float level and wenthigher in the main jets (from 70 to 72) and got rid of the back fire...hope this helps

 

I had a similar problem, the kickdown cable needed adjustment.

 

Unfortunatly there are so many issues with carburated cars.
Two more sugestions, I did alot of work on an 81 vette with electric choke, for the first 2-3 minutes whether the car was warm or not the electric choke would be engaged, a romp on the gas pruduced the same results that you are getting.
Second, don't laugh, but I have seen guys more than once work on thier cars, dial them in perfectly with the air cleaner off, think everything is great, slap on the air cleaner and slam the hood, then off they go it runs like crap. Then I point out that there air cleaner is black, and walla, problem solved.