I recently finished putting together a 302, I replaced the head gaskets, cam bearings/cam. My problem is the engine backfires through the carb only under load. I'll start by saying I think mechanically the engine is ok, my results of a compression test were between 150/155psi on all 8 cylinders. The backfire is one poof through the carb, not repetitively like a worn cam lobe. The block is an 85 that was previously TBI but now has an Edelbrock 1405 carb on a ford stock aluminum manifold. The ignition is an aftermarket Chevy style HEI distributor with the ford bottom. I verified spark on all 8 cylinders, I triple checked my firing order, and one of my questions is will a 302 run on both standard or HO firing order. The cam is barely a mild one just a few thou over stock, nothing radical. I'm not sure what's causing this it also sounds like it has a slight misfire, but revving it in neutral it seems to run fine until I let the clutch out, then pop and it stalls. Any help is greatly appreciated.