Re: Gaskets between head and exhaust manfold

[Glenn Merrell <gmerrel@domain.elided>]

Hello Duncan,
	As per the Stag Repair Operation Manual Exhaust Manifold Refitting section
30.10.26 paragraph 4 b. "No gaskets are fitted between manifold and head".  I
think that is the Official manufacturers recommendation for a standard cast iron
exhaust manifold to the cylinder head exhaust ports.  It would be extremely
important to make sure the surfaces of both the head and exhaust manifold were
clean and parallel, no scores, dings or pitting.

	In My Humble Amateur Opinion, when fitting tubular exhausts, the ones I have
seen are not (truly flat) plane/machined flanges and may have over 10+ thousands
variance across the flange.  The flanges are just cut out of a piece of 1/2 inch
steel with no additional machining, welding the tubes onto the flange distorts
the flange.  My option is to fabricate an exhaust gasket to fit between the head
and tubular header which is basically standard for headers in my book.  My
opinion on manufacturers not using head to exhaust gaskets is, I believe, an
economic one, as high temperature gaskets are expensive and usually asbestos.

	You raise an issue about heat transfer which I agree is a valid one.  The Stag
heads have a difficult enough time getting rid of heat and the cast iron
manifold is a huge heat sink either removing or retaining heat.  The question
is:  does the cast iron exhaust manifold aid in heat removal from the cylinder
head or add in retaining heat on the cylinder head and in the engine
compartment?  The cast iron exhaust manifold is insulated from the exhaust pipe
by a metal/fiber/metal gasket.   For me, I'm not going to speculate on the heat
sinking function of the cast iron manifold, they are off of my engine replaced
with SS tubular exhausts to free up the breathing a little, directing the heat
out of the engine compartment as fast as possible.

Duncan Miller wrote:
> 
> Should I use gaskets between the head and exhaust manifold? Maybe it
> would keep the heat from coming from the Higher temp. Manifold into the
> head.

In My Humble Amateur Opinion, Yours for speculation ... ;-}

Regards,
Glenn  Merrell
Triumph Stag Register USA VP
*J*O*I*N**Y*O*U*R**L*O*C*A*L**T*R*I*U*M*P*H**C*L*U*B**T*O*D*A*Y*
*Member of:
*VTR, RMTC, TSC USA, TSR, SOC
*73*S*T*A*G*****************************************************