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.

13.5 is not rich  enough with the ethanol fuel in my opinion.  I would feel safer with 12.65-12.85 at idle and under acceleration.  Float levels may be off even though you got the carbs rebuilt due to shipping and handling.  I still think you need a phenolic spacer, and 1/4" should be able to be fitted under the base of the carbs with the fuel line block moved up to match.  The lines could stay the same.  Joe-JDC

JDC