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Exhaust Manifold Gaskets

Posted By 312YBlock Last Month
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312YBlock
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Are exhaust manifold gaskets necessary on a 312?

1955 312 T-Bird Warwick, NY
Ted
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That’s a loaded question.  From the factory, exhaust gaskets were not used.  The exhaust manifolds simply relied on a metal to metal fit at the heads.  Once removed, the exhaust manifolds are typically reinstalled with gaskets due to some warpage taking place.  My experience has been that the gaskets tend to promote the manifolds cracking and/or breaking more quickly due to the gasket separating the two and there being a greater heat differential between the head and the exhaust manifold.  Said another way, the exhaust manifolds are distributing some of their heat back into the cylinder head mating surface when no gasket is being used which helps that manifold to run cooler thus slowing down any expansion that causes them to break.
 
More thoughts on this always welcome.

Lorena, Texas (South of Waco)


312YBlock
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Thanks Ted, good information. I’m planning on ordering 2 new manifolds and having them ceramic coated. I think I’ll install them without gaskets.

1955 312 T-Bird Warwick, NY
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use the gaskets, but use grade8 capscrews,aswell hardened flat washers(cat hardware would be my  preference as there flat washers are thicker and capscrews have thicker heads. my 1st y was a 1955 272,with no gaskets, constantly tightening the bolts.  just my warped way of doing things
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Make sure the manifold flanges are not coated. 
DANIEL TINDER
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312YBlock (3/3/2021)
Thanks Ted, good information. I’m planning on ordering 2 new manifolds and having them ceramic coated. I think I’ll install them without gaskets.


If the heads aren’t installed yet, take them & the manifolds to a machine shop first and have the mating surfaces leveled.  Otherwise, you’ll just have to install gaskets later on if you want to get rid of that ‘ticking’ sound (it’s usually not valve noise).  If you DO install gaskets, get locking manifold bolts, and DON’T over-tighten (just snug them down), as that will typically crack the ears.  After a few heat cycles, you can tighten (snug) again if leaks occur (don’t forget to unlock the bolts first), but the aluminized gaskets seldom need it.  Make sure the gaskets are trimmed so they match the port openings.

6 VOLTS/POS. GRD. NW INDIANA
paul2748
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If your not reinstalling the original manifolds, either have both mating surfaces trued or use  a gasket.  You don't know how true the new manifolds are and if there is warpage of the head mating surface.

I use gaskets.  I always tighten them just like an intake or head.  Start from the middle and go outwards.  First round just tighten all of the bolts to snug, then go over them to tight.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

KULTULZ
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IMO ...

My experience has been that the gaskets tend to promote the manifolds cracking and/or breaking more quickly due to the gasket separating the two and there being a greater heat differential between the head and the exhaust manifold. 

TED


Composite gaskets are asking for a failure. They allow different heat expansion rate (and expansion/contraction) between the two different components. If you are worried about a possible leakage, FORD offered steel shim gaskets with heat shields for later FYB truck engines (I think VICTOR still carries them).

Good quality hardware, thread-loc and possibly mechanical locks if you don't mind the non-stock look.

Again, IMO ...

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W (BY GOD) V - EASTERN PANHANDLE
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DryLakesRacer
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On mine the last cap screw on the fire wall end needed a header style bolt. 3/8” or 7/16” head and large flat flange.
I worked in the power plant industry for over 40 years and quickly found our smaller steam valve packing adjusting bolts were 3/8-16 with a 3/8” shoulder, flange, And 7/16” wrench head. After outages in the scrap bin I removed every bolt I could find. The greatest exhaust manifold and header bolts ever. Headman also had smaller OD lock washers that were thicker. Don’t have any of them left..

56 Vic, B'Ville 200 MPH Club Member, So Cal.
PF Arcand
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Just for info; What about the Copper exhaust gaskets that were available some time back?  They were advertised in Y-Block magazine at some point in the  past.. 


Paul


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