zz4 doesn't bog, it falls flat on it face at full throttle

[hjgator]

I bought a 1979 with a zz4 and a Q-jet in June. It stumbled a little at full throttle from a dead stop. Since it got cold, it falls flat on it's face, I had an GTO in 67 and a SS396 with a Q-jet, never had much luck with them, any suggestions.

 

[86-ZZ3]

I bought a 1979 with a zz4 and a Q-jet in June. It stumbled a little at full throttle from a dead stop. Since it got cold, it falls flat on it's face, I had an GTO in 67 and a SS396 with a Q-jet, never had much luck with them, any suggestions.

Doesn't a stumble indicate it's running a bit rich?

 

[KANE]

I bought a 1979 with a zz4 and a Q-jet in June. It stumbled a little at full throttle from a dead stop. Since it got cold, it falls flat on it's face, I had an GTO in 67 and a SS396 with a Q-jet, never had much luck with them, any suggestions.

Go Tuned Port...

 

[wishuwerehere82]

I bought a 1979 with a zz4 and a Q-jet in June. It stumbled a little at full throttle from a dead stop. Since it got cold, it falls flat on it's face, I had an GTO in 67 and a SS396 with a Q-jet, never had much luck with them, any suggestions.

Since the air temp seems to be affecting it, here's a few things to look at.
1) Thermostat operating properly
2) Check the Choke pull off opening the choke at operating temperature.
3) Check the Timing and vaccuum advance for proper operation.
4) I don't know what kind of air filter you are using, but if it's stock, Check the vaccuum operated diverter valve on the snorkle. It should be drawing air in from the heat riser during warm up, then from the intake horn at operating temp.
5) Check the carb to intake gasket for any vaccuum leaks.
6) Check the power valve on the carb. It may not be set rich enough. Cold air is denser than warm air, so it needs more fuel to keep the proper fuel/air balance. It might have been a little lean to begin with.

 

[gmjunkie]

Since the air temp seems to be affecting it, here's a few things to look at.
1) Thermostat operating properly
2) Check the Choke pull off opening the choke at operating temperature.
3) Check the Timing and vaccuum advance for proper operation.
4) I don't know what kind of air filter you are using, but if it's stock, Check the vaccuum operated diverter valve on the snorkle. It should be drawing air in from the heat riser during warm up, then from the intake horn at operating temp.
5) Check the carb to intake gasket for any vaccuum leaks.
6) Check the power valve on the carb. It may not be set rich enough. Cold air is denser than warm air, so it needs more fuel to keep the proper fuel/air balance. It might have been a little lean to begin with.

Check the accelerator Pump!! If it's not squirting enough,
IT WILL DEFINITELY FALL FLAT ON IT'S FACE!!!

 

[Chuck-75]

My 75 Vert. did the same thing. (before I did the engine swap.) after I removed the gas tank I found out that the rubber hose above the fuel tank was pinched and not letting enough fuel to pass, (go figure?) Factry? or bubba? check and this was my problem for full throttel problems.

 

[Koop]

My '69 is supposed to have a Vented gas cap, some joker put a non vented cap on it. Shake the gas up in a corner and it would expand and force feed the carb and flood, floor it and it would starve (suction in the tank). That was tough as hell to figure out.

Have fun.

 

[hjgator]

Thanks guys i appreciate the suggestions. Will give them a try.