Head bolts

[jalopi]

Nah, re-using tty bolts really isn't the best idea... this is basically why:



Sure, I guess you could maybe get away with it on dad/grandma's beige car that doesn't get driven hard, but if you're gonna beat on it, this is a BHG waiting to happen.

[jlevie]

yeah, they were defective. they weren't TTY I don't think either.

I believe they were TTY bolts and the flaw was that the heads of the bolts tended to separate. A fatigue problem with the alloy I believe. I have an engine from an 88 (130k) that never had the recall done. Four of the bolts had fractured heads.

Except in the case of an M20 being built for FI, TTY bolts are the best choice. The tightening procedure takes the bolt past the elastic limit and into plastic deformation. The loads on the bolts (except in the case of a serious overheat) will never exceed the elastic limit. Which means that the clamping force will always be correct. TTY bolts are used for turbo applications also. A different alloy is used to move the elastic limit higher.

Regardless of whether head bolts are TTY or not, it is critical that the threads in block be chased, clean, and lubricated with a light oil.