Thread: exhaust backfire

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My Nova 454 was runing very rich had carb (750 vac. secondaries) apart several times there realy isn't much to a Holley. changed gaskets changed jets so many times I don't remember whats in there anymore. Got another 750 manual secondaries. placed it on and started the engine. I have not checked the carb as it was good on the engine it was removed from..now I have a backfire in the engine , it's not all the time but it happens. there is no cat on this car. it is dual ex. and the B/F is on the pass side. This just started today so havent had time to realy get into it any sugestions

Charlie, are you driving the Nova, or sitting in the shop tuning? Is the backfire on deceleration, steady load, or when? Could you have run too rich for long enough to carbon it up and create little hot spots of carbon, lighting off residuals at the wrong time? Really just guessing here, tossing out first thoughts to get the dialog going?

yes under load or in shop. I thought aboutcarbon build up also I will pull the plugs and take a look. There a things to look at if it was all the time but its not anything regular. Thanks for the reply. Seems you get one thing under control and another pops up I know I'll get it just have hard time taking it seriously yet.

I know you know it, but a small air leak in the exhaust system can fuel a lot of popping, and it's one of those simple things we often overlook, especially if the exhaust is loud and masks the leak.

On another forum, a similar problem was caused by the vacuum advance sticking (retarding the timing). You may want to check the distributors vacuum port and make sure there are no vacuum leaks at the carb.

Is this carb a 2 needle adjustment or 4 corner? If it's a 4 ,sometimes getting them adjusted can lead to some backfiring. I know, I had one and it gave me fits til I got it right.

Yep 4 corner,but I think my problem was the plugs I changed them and so far all is good the ones removed were BLACK from rich mixture