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.

Before I sent the carburetors away to be rebuilt, I blocked off the outer carb ports on the intake and ran it on the center 2bbl. I did not experience any sort of pop or backfire on acceleration. I don't believe the intake is leaking. I referenced a head to head article that Mr. Eaton posted and the intake I have is listed as a "large port" I have swapped the jets in the carbs to the 59P and 67S. I'm going hunting for the correct fittings for rubber fuel hose tomorrow. Spacers are set to arrive on Friday. I'll put everything back together then and see how it goes.

Well. I've swapped for rubber hoses. Added the spacers. Adjusted jets to 59P and 67S. Adjusted timing to 12⁰ btdc. Intake temperatures are about 170 ⁰ across all three carbs. Adjusted idle and mixture screws. Same symptoms. The only other thing I can think of is maybe the secondary carbs collar is set too far back, so I'm not activating them when I need to. I don't really know what else to do.

What distributor are you running?  In an early post with a picture of your engine, the distributor is not visible, but the firewall  is '55 or '56.  Are you running a '55 or '56 all vacuum advance distributor.  In your last post, you wondered  if the secondaries are coming in  too late.  How soon do the open.  Maybe they come open to soon and do not have enough air flow  to start the fuel flow.  Do you have accelerator  pumps in the end carbs?

John - "The Hoosier Hurricane"

I have the later style distributor. I believe it's a 1960. Outer carbs have plugs in them. No power valves.

Are you by chance using a Pertronix ignition in that distributor. They can give you these kind of problems

SE Wis

I am using the pertronix ignition. I've read that when the pertronix fails, that it is just completely inop though. I had this distributor in my last 292 2bbl and I didn't have any trouble out of it. It ran ok on this new engine with the outer carbs blocked off as well. Not to say that it couldn't have malfunctioned between then and now though.