Hey everyone. Recently rebuilt an '88 Camaro 305 to go in my 78 280Z. Different, huh? Anyway, The engine backfires through the intake manifold (blowing gas out the top of the carburetor. I tripled checked the timing (including pulling the timing chain cover) and confirmed the distributor was pointing to #1 cylinder. I even removed the intake manifold & valve covers to visually see if all the valves were closing. I didn't pull the camshaft (though I probably should have) when I replaced crankshaft and connecting rod bearings, but noticed the engine has roller lifters. Did Chevrolet use roller lifters in 1988? Do you think the cam could be causing the backfire issue?
I have the engine on a run stand. The engine got hot and cooked the main bearings. I think the oil pump went out.
I'm a bit frustrated at the backfire issue and am interested in any opinions about what it might be. Kinda like another set of eyes.
Thanks in advance for any and all opinions on what the problem might be.

 

Double check that your plug wires are in the proper order and that you distributer is not 180 degrees off

 

If gas is blowing out the top of the carburetor, your timing is 180 degrees off.

The only time I dealt with that was when the timing chain on my 1977 Pontiac slipped, due to missing teeth on the crankshaft gear. Back then, to make the engine quieter, GM had put phenolic teeth on the steel gear body, and half the teeth had stripped off and ended up in the oil pan. I replaced it with a 100% steel gear, and spend July 4th weekend in the driveway working on the car to get things back in timing and running again. It was a matter of getting the camshaft and crankshaft gears and distributor all lined up to the right marks and positions, and working the gears and chain back onto the shafts.