Good morning all. I've been working on a 292 with a 3x2 intake for several years now. I've gotten to a point where I can drive the vehicle for short trips, but I'm intermittently getting a backfire under acceleration once the engine warms up. Its also cut off on me twice at a stop. I think it might have been vapor lock, because it restarted pretty quickly. Ive sent the carbs out to be professionally rebuilt. I called the cam manufacturer and my initial timing is where it should be. (10⁰ btdc) I've been trying to do some research about what else might be causing my concern. I'm wondering if I'm getting an issue from the heat riser ports running under my center carb. I'm using the wide open gaskets, not the truck ones with the smaller opening. Could this be my issue? I'm trying to make the power tour this year and I'm running out of time. Any help would be appreciated. Cam is an isky 301333, Weiand intake. 292 bored .090 over. Red's headers that have been ceramic coated to lower under hood temps, gasket-match porting on a set of G heads.

Have you jetted up for the ethanol in the fuel?  I would install a 1/4" phenolic spacer under each carb, remove the metal from the intake gasket heat riser hole, block the heat riser with a thin piece of metal, and set the initial timing at 12-14* and try it again.  You can get the spacers from Speedway in various thicknesses.  Backfiring is typically caused by lean mixture of fuel.  Joe-JDC




JDC

I have not touched the jetting at all. I sent them away to Charlie Price at Vintage speed. Like I said, there is no metal in these intake gaskets at all. Ive set up an air fuel gauge with an oxygen sensor to monitor the mixture. Its at about 13.5 to 1 at idle. I am intentionally leaving it rich to avoid the lean condition. I have hard lines bent for my fuel already. If I have to go back and make those again due to a spacer, I'll pull the entire set up off and sell it.