Mystery engine roughness

[L88 crazy]

What's up corvette owners!!

My 72 Corvette is running a little sick lately. When accelerating hard or starting at a green light. Runs fine until on or about 2000 to 2300 RPM no matter how hard I am on the throttle. At that time it sounds she is running on half the cylinders in the engine. Sounds like the cylinders are getting loaded up with too much gas or something. Has anybody else had this problem besides me? I don't get it.

 

[cntrhub]

First things first. Since you think the car might be running bad, you could pull the spark plugs and see what the burn looks like? Are the plugs oil fouled (shinny) or gas fouled (dry sooty)?
Now back to the first thing first rule. Check compression on all cylinders. You will have all spark plugs out for easy engine spin. And you will need to remove the coil wire from the distributor cap, so the fuel pushing out of the spark plug holes don't start a fire.
Next is to chase ignition. And next, a fuel delivery problem. That is the order I would take in my diagnosis.
Want to forgo all that trouble? Check your ignition timing and see if your are on the timing mark and then check for ignition advance.

 

[brusso]

I agree cntrhub. Esspecially the timing issue. Sounds like, at that RPM, that the (ported) vaccum advance is working. May possibly be that the mechanical advance (centrifigal) isn't.

I88 crazy If you have access to a timing light that has an advance control, you can easily check all four timing values.(base, vaccum, mechanical, total) I think that ballpark total @ about 2500-3000 rpm is 35-40 degrees btdc. Also being a 72 I assume that it has points. Check-em for pits and alignment. Finally, there are so many aspects to fine tune an engine. But there are only three things that a car needs to run. (fuel, spark, timing). Good Luck!

 

[cntrhub]

brusso says, "But there are only three things that a car needs to run. (fuel, spark, timing). Good Luck!"
brusso, i think you meant the 3 things to make any engine run is fuel, spark, and, "Compression." I'm sure that's what you meant to say.

 

[brusso]

Well OK. Three things that are not inherent to an engine and are provided to the engine by some sort of accsessory required for the engine to run are.....?