327 serious problem
 

This is a stock rebuild of a 250hp 327 (owned by a friend). The engine only has 100mi on it and it was pulled due to a severe vibration. I can see that the exhaust valves show signs of over heating, but I'm not sure what the deposits are on the pistons. Maybe it's running so lean that it's melting the aluminum? He says the plugs are "clean". He was using Sta-Bil in the gas.

Any ideas anyone?


Verne


Attachment 181283

Attachment 181284

Severe vibration? Explain more? Is the harmonic balancer bad? Is the crank straight? How is the flywheel or automatic flex wheel? Sounds like to me its out of balance with parts i am listing? Not enough info to figure out what he means by this severe vibration? Was the timing to far advanced? Carb adjusted correctly? This engine does not have high compression.

The vibration might have been severe detonation, but that should have cracked the ceramic in the plugs. It does look lean, but I'm no expert.

Did it do it after the rebuild or after a few miles?

Got a pic of the plugs?

I can ask for a pic of the plugs. He said the vibration starts at about 1200rpm and gets worst up to about 35-40mph. He can feel it in the seat and it's bad. He said all the normal suspects have been checked, ie: tire balance, driveshaft, pulleys. The mechanic said he checked the crank and its good.
Right now my question is what caused the appearance on the piston?? The mechanic says the problem is the gas and the carb and that's why he was referred to me. But I disagree that a carb problem would cause a vibration. Maybe a miss or hesitation, but not an actual vibration.
I'll be speaking with him later for more info.


Verne


He just sent this pic of a plug. They all look like this and they look fine to me.
Attachment 181322

Could it be the harmonic balancer has spun on the rubber ?
I had this problem years ago on a L-S6, unbelievable vibration.
Bruce

Catastrophic Engine destroying detonation can be heard from the roadside when occurring on a passing vehicle.

WOW those valves look overheated.
Piston looks like cooked on oil -
a flat top in a 250 hp 327 hard to believe there were detonation.

Are all four tires balanced? Has the car been given a proper alignment? Has the car been sitting for a long time on it's tires? Maybe the tires have flat spotted?

I mentioned this too. Harmonic balancer could be bad. Never heard of a bad vibration caused by timing. I am sure the timing was set correct when starting engine and then make sure it was correct before driving the car. Same goes with the carb. To me if he got 100 miles on the engine without the bad vibration, then all of the sudden it started and can feel it when sitting in the seat, it could be a drive train issue. Before i would of ever torn the engine back down i would of done some real research on the problems i mentioned. Driveshaft out of balance? bad u-joints? loose flywheel, flex-plate? This is not a hi-perf engine here. Have the crank checked again. Out of balance? Check harmonic balancer. Check complete drive train. Dont over look anything. Its could be an obvious thing. Let us know.

The black stuff looks like deposits from octane booster. You wouldn't think it would need octane booster with flat tops. Can't imagine he put enough Sta-bil in there to cause deposits.

Pretty easy to isolate engine vibrations from anything else. If it is in the engine, it will vibrate with the car sitting still. If you suspect driveline, turning the engine off while coasting in neutral will eliminate the engine.