Exhaust manifold bolts coming loose


http://forums.y-blocksforever.com/Topic169571.aspx 		Print Topic | Close Window

By RossL - 2 Weeks Ago
I installed new exhaust manifold gaskets about 4 months ago (1955 Tbird 292).   I tightened them down and after running it a couple of times I tightened them again.   I checked them this weekend and a couple were not tight, they needed 1/8 of a turn.   I heard if you tighten them too much the manifold could crack.

I obviously have to go a little tighter, is this common?   I thought I read someone else had a similar issue.
By Deyomatic - 2 Weeks Ago
I'm no expert, but the 292 in my hot rod does the same thing.  Every few months or if I hear a "leaky exhaust sound," I'll just re-torque them.  

Someone here will likely have a real fix.  
By DANIEL TINDER - 2 Weeks Ago
One of the speed shop parts catalogs may still offer ‘locking’ manifold bolts. Once snugged down on the gaskets and locked with their central allen/hex bolt, no leak noise after 70K miles/20 yrs.for me.
By paul2748 - Last Week
Are you using lock washers ?  The star lock washers may work better that the usual  lock washer.
By KULTULZ - Last Week
You don't want to use a composition gasket on an exhaust manifold as this will be the result. The cyl head and manifolds expand and contract at differing rates causing the loosening.

It is metal to metal or steel shim if needed.
By DANIEL TINDER - 2 Weeks Ago
KULTULZ (1/3/2026)
You don't want to use a composition gasket on an exhaust manifold as this will be the result. The cyl head and manifolds expand and contract at differing rates causing the loosening.

It is metal to metal or steel shim if needed.


Since the manifolds & heads are seldom perfectly flat, the comp. gasket takes up the expansion/contraction slack, preventing leaks if the bolts never loosen. Just make sure to not initially over-tighten them and snap off a manifold ear. The alternative using the factory metal-to-metal system is likely frequent retorquing, though having the manifold & heads milled may prolong the seal (?).
By paul2748 - Last Week
No problem with using the composition gaskets.  I have used them on both of my yblocks with no problems - leakage or breaking.  If you install the manifolds   correctly, I doubt you will ever have broken ear.  I use lock washers on all the bolts.
By RossL - Last Week
paul2748 (1/3/2026)
Are you using lock washers ?  The star lock washers may work better that the usual  lock washer.


I am using flat lock washers with Felpro exhaust gaskets