Help!!! Flywheel bolts keep coming loose

[78chev]

Hi everyone! I have a 1978 Chevy C/10 Stepside that has a souped up 250 inline 6 with a cam and 2 4-Bbl carbs. For some reason, the flywheel bolts keep coming loose. I have not worked on it myself, but the shop that has tightened the bolts and it happened again. After that, they replaced the bolts and used red loctite. It has come loose a third time now and not sure what is causing it. The mechanic who specializes in classics has no idea what is causing it to happen. Has this issue happened to any of you guys? If so, what was the fix? The transmission is a straight-tooth.

 

[Rickf]

I'd look at the threads on the crank. What's the 4Bls CFM? What's your redline?

 

[Bextreme04]

Hi everyone! I have a 1978 Chevy C/10 Stepside that has a souped up 250 inline 6 with a cam and 2 4-Bbl carbs. For some reason, the flywheel bolts keep coming loose. I have not worked on it myself, but the shop that has tightened the bolts and it happened again. After that, they replaced the bolts and used red loctite. It has come loose a third time now and not sure what is causing it. The mechanic who specializes in classics has no idea what is causing it to happen. Has this issue happened to any of you guys? If so, what was the fix? The transmission is a straight-tooth.

I have NEVER seen a properly torqued flywheel bolt come loose. Either that mechanic hasn't had his torque wrench calibrated in too long, or he didn't do something right. Loctite needs clean threads to really work properly. What torque did the mechanic say he used? Were they just stock flywheel bolts or ARP?

 

[squaredeal91]

Maybe the bolts are too short. Or the flywheel is the wrong one.

 

[legopnuematic]

Speculating but almost sounds like the flywheel is not seated fully on the crank flange or something. Whether its from a burr, machining issue, issue from prior problems can't say without more details.

Also agree on the bolts and threadlocker, holes have to be clean otherwise the threadlock won't do what its supposed to. But at proper torque I would think they still wouldn't loosen up like that repeatedly. Are the bolts the correct grade? If someone tried to use like grade 2 bolts stretch would be a possibility. ARP makes nice bolts and (last time I bought them) were not unreasonable in price.

 

[Buck69]

Did they bar the engine over and check the runout of the flywheel after torqueing it? Sounds like they are overlooking something.

 

[JBswth]

Possibly the flywheel is the wrong one, and is slightly loose on the hub, or the bolt holes are too large. Never heard of that happening, so only guessing.

 

[nvrenuf]

Wrong bolts bottoming out on the shoulders?

 

[DoubleDingo]

As others have said, the bolts should not loosen. If this has happened over and over, I'd also question the integrity of the threads on the crank. Thread locker is not normal on flywheels or flex plates.

 

[idahovette]

What about the security lock washers that go with the bolts?? No mention of them?

 

[SquareRoot]

Tack weld em