chevy 350 runs rough wont idle shoots flames, gas or puff threw carb..... - Third Generation F-Body Message Boards

86Stevo · 11-07-2009, 04:48 PM

like i stated in the title i have a chevy 350 runs rough wont idle shoots flames, gas or puff threw carb, the motor is bored .30 over has a mild cam dunno the specs or what type, high rise holley contender intake with a qjet on it. the cam and crank are in time my dist. is set right, the car starts up eh need to push the gas and it shoots up in rpm dropps down and stays around 2500 and then some times it will backfire threw the intake some times it wont, some times it will idle around 2000rpm some times at 6500rpm i have no freakin idea what the hell is going on with this car i switched out carbs to another qjet almost same exact problem put a holley double pumper on same problem but dosent really backfire much, any ideas or help ? i need this car up and running asap. can valuves that are out of adjustment do this ???

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toomany · 11-07-2009, 09:30 PM

If the idle is jumping around then it could be a vacuum leak. Start the car and spray some carb cleaner around the base of the carb and where the intake meets the heads. If the idle changes then you've found a leak.

The backfiring can be because the timing is off. Although I've seen motors that were to lean do it too.

Gumby · 11-07-2009, 09:44 PM

Id be leary of sprayin carb cleaner around if it shootin flames

Id try to more direct $5 propane torch, all its gonna do is go POOF and be gone [maybe your eyebrows too

], carb cleaner could burn enough to catch sometihng else on fire. Don't wanna suck up fire extinguisher stuff into a running engine.

Seen your post earlier n have no real suggestion cept that something is wrong, start with the basics. Recheck everything, maybe even take a break fomr it to clear your mind as sometimes keeping at it doens't help.

camaronewbie · 11-07-2009, 10:02 PM

Every backfire through the carb I've ever seen meant bad ignition wiring - something is crossed on the dist or the plugs, or one or more wires have a break in them - double check firing order and test continuity on all the plug wires.