1992 Miata, LS1, then LS3 swapped

[GySgtFrank]

Originally Posted by mazpower

It started making a weird thumping sound in Louisiana...about 1800 miles into the trip. I thought it was the tranny but a friend suggested I replace the throwout bearing. So we did that outside the cabin when we got there and the noise persisted. Found out last weekend that it was because 5 of the 6 flywheel bolts came loose. I followed ARP's torque specs, so much for that. I used red loctite this time, hopefully they don't come loose again.

I was crewing for a stock car running a chevy 250 straight 6 a number of years ago. Had the same problem. No matter what we did it would spit off flywheels, even the LocTite didn't help. It turned out it was some sort of weird harmonic that kept loosening the bolts. We put a Fluidampr front vibration dampener on it and it cured the problem.

[mazpower]

Originally Posted by GySgtFrank

I was crewing for a stock car running a chevy 250 straight 6 a number of years ago. Had the same problem. No matter what we did it would spit off flywheels, even the LocTite didn't help. It turned out it was some sort of weird harmonic that kept loosening the bolts. We put a Fluidampr front vibration dampener on it and it cured the problem.

Interesting...I'm running a SLP front dampener on this build cause its keyed, as is my crankshaft and I wanted solid timing marks (LSx engines don't have keyed pullies or cranks from the factory, no timing marks either). The engine is pretty damn smooth through the rev range. I've heard that spec clutch assemblies can be out of balance though, I wonder if that contributed to it? I've been running the same flywheel/clutch combo since the beginning and this is the first time I've had this happen.

[GySgtFrank]

Originally Posted by mazpower

Interesting...I'm running a SLP front dampener on this build cause its keyed, as is my crankshaft and I wanted solid timing marks (LSx engines don't have keyed pullies or cranks from the factory, no timing marks either). The engine is pretty damn smooth through the rev range. I've heard that spec clutch assemblies can be out of balance though, I wonder if that contributed to it? I've been running the same flywheel/clutch combo since the beginning and this is the first time I've had this happen.

It may not happen again, who knows. The six we were running had been internally balanced when the engine was built and it ran very smooth. Had the flywheel and clutch rebalanced too, didn't help. One of those weird things that you couldn't really tell just listening to it. It may be a balance issue or like you said it may just be the bolts, maybe something else. Have to see if it holds this time.