I need some help.
96 4.3L V6 Vortec just rebuilt, but can not figure what is wrong.
Block and heads and carb were professionally done by reputable machine shop and carb shop and every mechanical thing was newly installed.
New plug wires, cap,rotor and coil as well.
Motor starts and idles, but when attempting to rev up past 1350RPM, it starts to stumble and acts like it goes out of time popping through the exhaust even though I have put a timing light on it and set it.
During assembly, I made double sure the cam and crank timing marks lined up before installing the chain.
Could the module be causing this? Anybody shed some light?

Sounds like it might be going into LIMP HOME mode--that is caused be one or more of sensors giving MEFI data that says some condition would cause severe/catastrophic failure.

Double check connections to all senders--water temp, oil pressure, and many more.

Are you sure you have the firing order right? Since your engine is carbed it won't have a power reduction (limp home) mode.

Dave

Dave: Firing order 1-6-5-4-3-2 is what I was told.

Rechecked the firing order & ran it again in hope of change. Nope, it back fires through the carb as well when you give it gas. I hate to say this, but does this sound like cam timing to anyone? I was pretty sure that the marks were lined up. Don't know what else to try. Would bad lifters do this?Anybody else?

It might be a valve not closing / out of adjustment that would account for the backfire condition. just thinking out loud.. Good luck,

RHC

Miss adjusted rocker/cam timing off would be my guess

Try re-installing the distributor but start from sratch. Bring #1 tdc etc etc. Sounds like its a tooth off.

What is the base timing set to? Is the advance working?

Who and how did the valves get ajusted, how does it idle ,fouled plugs wil cause poping.tight valves will cause motor to rock side to side ,did it start right up on first try ,continued cranking trying to start could foul plugs.