Backfiring 79 when punching the gas
 

I've got a 79 with 75K miles (bought it for a song 2 years ago). Drove okay initially (after I got it running, new plugs, points, and ballast resistors, this year new starter motor). Some hesitation at 5K rpms but not above.

Then the idle was irratatic and I found the idle compensation valve was broken. Plugged it and adjusted the idle (didn't need much). I'm not sure about the mixture, I have no exhaust analyzer but it smells like a first gen, nasty.

Anyway, when the idle was rough, and it was about to die, I'd gun it a bit (rev up to 2K or so) and it backfires (some small backfires but also some huge ones).

It can do this anytime I need to accelerate (up hills in any gear). Now that the idle is okay and it doesn't die, I can drive around without scaring women and children but I can't gun it (which is a shame, quick acceleration is what the car is about).

Any ideas guys?

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Before the backfire, the engine bogs down sort of hesitates then KAPOW off it goes zooming up the hill or reving up the rmps.

well, i have a '79 also, and from what ive gathered the backfiring is something u just gotta buck up and deal with when owning a rotary. Ive heard some say that new exhaust may clear up the backfiring sound, but mine does the same backfiring thing, however thats only when i let off the gas. But in my opinion, if it doesnt affect the performance of your car, feel free to gun it, a little popping here and there never hurt anyone.

if it's backfiring before you take off, then something isn't right.. backfire on decelleration is normal, but on the way up... might wanna check the timing.

I know backfiring while slowing down is normal, small little pops.
I'm getting huge gunshot backfires when trying to accelerate. The car lugs a moment big backfire then can move forward.
Do you think it's the leading timing or trailing? The plugs never looked great but not consistent with one another. Carbon buildup and/or oily.

its a very lean condition. If nikki carbs have them, the accelerator pump sounds like it is malfunctioning. When you press the gas, you open the butterflies suddenly, and the vaccum behind them pulls a big gulp of air into the engine. The accelerator pump shoots alittle stream of gas into flow to richen it up. If there is no stream, there is not near enough gas for the volume of air, it doesn't ignite in the cylinder, then the unburned gas and air go out the back. As soon as the carb catches up with the flow, it runs right again. Check your accel pump, most likely the problem. I have have to work on pump significantly to remove thjat hesistation. I am no expert, so maybe someone will say I am wrong on a nikki, but that would be it on a holley.