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By RossL - 2 Months Ago
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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.
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By Deyomatic - 2 Months Ago
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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.
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By DANIEL TINDER - 2 Months Ago
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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.
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By paul2748 - 2 Months Ago
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Are you using lock washers ? The star lock washers may work better that the usual lock washer.
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By KULTULZ - 2 Months Ago
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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.
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By DANIEL TINDER - 2 Months Ago
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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 (?).
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By paul2748 - 2 Months Ago
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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.
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By RossL - 2 Months Ago
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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
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By oldcarmark - Last Month
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Maybe the Manifolds are NOT flat. They can be re-surfaced by any Machine Shop. I did mine because they would start to leak after some use and the Gaskets that I used to seal them would burn out. Not supposed to require Gaskets if the Manifolds are in fact flat and not warped.
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By KULTULZ - Last Month
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They came from the factory metal to metal and there was a reason for that.
You ascertain correct surface(s) flatness and go from there.
If you want something that will not loosen, you go to tubing headers where you can apply constant torque.
Main reason for ears cracking.
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By Big Tim - Last Month
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The only y block I have seen that the exhaust manifolds didn't leak as you described had the factory style lock washers that you bent around the sides of the bolt heads to keep them from turning. I just chalk re-tightening up to routine maintenance on these things.
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By 55blacktie - Last Month
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The exhaust manifolds on my 55 Tbird weren't leaking when I started tearing down the engine, and no broken ears. They are the original manifolds.
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By Ted - Last Month
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I have been using Nord Lock washers on the headers on my FE powered 1966 Fairlane and they do a good job in keeping the header bolts from backing off. Here’s a picture of what they look like.
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By RossL - Last Month
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Ted (2/10/2026)
I have been using Nord Lock washers on the headers on my FE powered 1966 Fairlane and they do a good job in keeping the header bolts from backing off. Here’s a picture of what they look like.
I liked this solution. I bought a set of Procom header bolts that come with similar washers.
Unfortunately the heads of the bolts (3/8 16) were too small for the holes in my manifolds (For some reason the holes are larger, except for the hole in the middle).
The heads are all 3/6 16 threads. Does anyone know if the bolts are supposed to have a shoulder to make up for the larger holes (my bolts do not have a shoulder)? I wonder if all this play causing the bolts to come loose????
The picture is one of my original 1955 292 manifolds. I bought a set of reproductions and they are drilled the same
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By Ted - Last Month
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By design, there are larger holes in the exhaust manifolds to allow for heat expansion of the manifold. Typically one hole will be smaller than the rest just so that the manifold is positioned correctly to the cylinder head.
Here’s a link showing a video where the wedge-locking washer technology is tested at a 4000 lb. clamp load.
Bing Videos
And here’s another option for a positive locking bolt where the exhaust manifold bolt holes may be too large for a conventional lock washer.
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By KULTULZ - Last Month
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- WHEN ALL ELSE FAILS -
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By RossL - Last Month
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I am going to try Summit Racing™ Split Lock Bolt Kits SUM-910120. They have an internal Allen bolt that spreads the end of bolt to hold it in place. I bought some thick hardened washers because these heads are also too small for the manifolds. I am going to put some anti-seize on the internal bolt
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By DANIEL TINDER - Last Month
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DANIEL TINDER (1/2/2026)
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.
Again, worked for me, though what effect was added by the foil-bound gaskets I used is another issue (?). Not sure offhand where obtained, but likely a T-Bird parts source.
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By RossL - Last Month
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DANIEL TINDER (2/26/2026)
Again, worked for me, though what effect was added by the foil-bound gaskets I used is another issue (?). Not sure offhand where obtained, but likely a T-Bird parts source.
I am in the process of installing an oversized remote power brake booster (for the first time) which will limit access to the exhaust manifold bolts on the drivers side (55 Tbird). Did you have to re-tighten the bolts at any time after you installed them? I am not going to be able to start the car for a couple of weeks, due to other projects. The spec for the bolts is "not to exceed 20 lbs", hex key is 6 lbs/72 inch pounds.
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By DANIEL TINDER - Last Month
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RossL (2/28/2026)
DANIEL TINDER (2/26/2026)
Again, worked for me, though what effect was added by the foil-bound gaskets I used is another issue (?). Not sure offhand where obtained, but likely a T-Bird parts source. I am in the process of installing an oversized remote power brake booster (for the first time) which will limit access to the exhaust manifold bolts on the drivers side (55 Tbird). Did you have to re-tighten the bolts at any time after you installed them? I am not going to be able to start the car for a couple of weeks, due to other projects. The spec for the bolts is "not to exceed 20 lbs", hex key is 6 lbs/72 inch pounds.
No. Never touched them again. Once snugged down on the foil-bound gaskets, no more leak noise. Wish I could remember if I had thought of using anti-sleaze on the central Allen bolts though. Will otherwise likely have trouble when comes time to remove the manifolds.
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