Driving home the engine started to sputter out. Limped home. Engine is an older 350, no work done to it. when it runs now, sounds like a V6, instead of a healthy V8. Changed the fuel pump, spark plugs are good and getting spark, compression test is good and even across the board. At a loss now for what it could be.
All above , Check timing to see if it moved , 10-12 deg initial at idle , Timing Chain ,,, HEI will burn hole in Rotor button & cap to coil ark, pole to pole ark inside cap ,
You need to know if the trouble is one cylinder or they are all suffering. Older Chevys can sometime lose a cylinder from rocker failure.
Not giving us a lot to work with...so most responses are going to be guesses...my guess is ignition related.
Right now, this is the best answer of the 7 posts you got. Several of the others are good simply because they suggest the normal list of trouble shooting things one does when suddenly a rig doesn't run right. First did you change anything including buying gas not long before this happened? Second if it happens to be an OT engine donor type rig per HAMB thinking did you maybe go through a big puddle not long before it happened? What does the exhaust sound like now? I'd change the fuel filter simply because that is maintenance and they do clog up if you get some dirty gas and often clog up on a just got together and drove it rig with an old tank. If it has HEI along with what was said about checking cap and rotor look real close at the wires on the pickup coil. They are prone to breaking after flexing back and forth over the years. I have a rig that I should be looking at right now on rather than sitting here. While you have the cap off check for slop in the timing chain as it may have jumped time do to a worn out chain or plastic timing gear. DO NOT change more than one thing at a time if you are one of the guys who tests by swapping parts.
Any other new noises since the problems began? Knocking, ticking, backfiring thru the intake or exhaust? Normal oil level and pressure, fresh clean oil, engine running at normal temperatures? As mentioned already, valve train problems would be worth looking into. Timing gear and chain, worn camshaft, sticking lifters, bent push rod, broken rocker arms, weak or broken valve springs, loose rocker adjustment nuts, rocker studs pulling out of heads, etc.
Not sure what your 350 is installed in, but in the old days, stock exhaust systems from GM were "double wall" pipe. Inner pipe would get too hot and collapse or curl up restricting exhaust flow.....outside of pipe still looked perfectly round.
Diagnostic.... While the engine is running, pull one plug wire off, listen and put it back on. The engine should stumble when the wire is removed. If there is no change, you have found the offending cylinder or cylinders. They make insulated plug wire pullers to prevent shock. High mileage GM engines can “pull studs”. The rocker stud can start coming up. This may or may not show with a compression check. A dirty check is to pull the valve cover and lay a straight edge over the rockers. If any are excessively high that may be the culprit.
A vacuum gauge will show up a clogged exhaust really fast. Most I have seen will make a loud "hiss" out the tail pipe. If you have 2, see if one side is worse than the other. When I was fixing cars around 1978, we would get new-ish GM cars in with the separated exhaust.
thanks, saved me some typing, but like you said, I would start with pullin one plug wire at a time.. could also be a plug that bridged over the ground strap
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