The valve timing is off
Answersounds like a possible worn camshaft lobe. a fairly common problem on late 70's Chevy small blocksIt's lean. You have to figure out why.
In late 1987 chevy went to fuel injection on ALL there engines. From 1987 down will have a carburetor.
When an engine backfires aka (burps) back through the carburetor this usually indicates a lean fuel to air mixture or an intake leak( which is more noticable at low RPM). When the an engine afterfires, aka (farts) out the tailpipe it usually means too rich of a mixture or unburnt fuel is entering the exhaust system
on top of the engine, under the air cleaner
Backfiring is usually an indication of a lean condition. When it does it during cranking, it's probably timing related.
Start and run, no. Cough, backfire, yes.
17-22 Hg
The 1996 4.3L engine doesn't have a carburetor, it is fuel injected.
Chevy 409 is a big block V8 engine. It was produced by Chevrolet from 1961 to 1965. It was a 6.7L engine, with a single or dual four barrel carburetor.
If your engine has a carburetor the filter is in the supply line into the carburetor. If your engine is fuel injected the filter is right next to the gas tank in the fuel line.
Chevy stopped using carburetors on there engines in 1987. Your engine is fuel injected if it's factory. And the unit on the top of the engine that you call a carburetor, is really called a Throttle body
The 95 engines do not have a carburetor, They are fuel injected / TBI Throttle Body Injection and there is no ajustment on them what so ever. You have other problems. Is check engine light on ?? If so then have engine scaned with an engine scanner and you will find your problem. I have a 95 Chevy 5.7 and its got a carburetor. I really don't know anything a bout them though. Sorry