Holley carb

running a early 327 with the l-79 intake manifold with hooker headers and msd ignition and a mild cam- engine is strong and wiring timing etc up to snuff however the car has a carb backfire on quick acceleration and hesitates on accelerating in a normal manner- it seemed to hesitate in the geginnig and now it is worse with the backfire out of the carb prevelent- the four barrel has for jets # 28 and the cam is pink and on the first notch the accelarator pump works with the gas peddle linkage and the vacuum was ok a year ago- what Holley would you use with this setup and should I change to larger jets and a different plastic cam as it is running lean- the plugs must now be foweled and I will check them later- where would you start on the Holley to eliminate or help the problem- as this motor is set like a l-79 I wonder what Holley carb and jetting and cam it would like- yabbering on so please chime in if you have been down this road or have some thoughts Ron

The lean condition on acceleration is a accelerator nozzle issue.

I guess when you say jet, you mean the nozzle is a #28

Change to a #31

Al

When it backfires through carb. It is either a timing issue or it is lean. I agree with Al, put a 31 squirter in it. Make sure the idle mixture screws are adjusted correctly also. That will cause a hesitation under light acceleration just off of tip in.

It sounds to me like you may need to advance the timing. That's always the first thing to try. It's quick and easy and if you don't try it first you could be in for a tail-chase messing with the carb.

It sounds to me like you may need to advance the timing. That's always the first thing to try. It's quick and easy and if you don't try it first you could be in for a tail-chase messing with the carb. it is not timing as that was easy to check- it is a backfire from the carb on a quick hit for acceleation and a hesitation to not wanting to increase speed even on moderate acceleration- it is my understanding the idle jets are just that idle jets- the acceleration and extra juice are handled by the acceleraor pump system-pump diaphragm-pump cam-pump nozzle- I think I may have to chase the carburetor for peace of mind. The accelerator pump system has to work with the throttle arm- as you hand pull the throttle arm the fuel should come out evenly on both ends- and in doing this little test I noteced one end was not getting the same spray as the other- if they were close it would be tough to tell but mine were odvious thus the carburator will get a rebuild from a check stamdpoint adjust the float level and accelerator arm with throttle arm and replace nozzles. This is the chase Holley advises if you have exhausted all other issues- barking up wrong tree is something I do sometimes but giving up is not an issue- what Holley carburator did the l-79s come with in 1966- thanks Ron