I was particularly thinking of the Fiat 124, and the Toyota pickup
truck. The manifolds are nearly identical to the Spitfires.
Both used a cast iron upper manifold.
Both used a twin tube lower pipe.
Both used three nuts to affix the two to each other.
Both used bell housing support straps as well.
Yet neither of them have any problems with blowing out exhaust gaskets.
So why does a Spitfire apparently have a problem with theirs? I don't
know. Don't see enough of the Spitfires two piece manifolds over on
this side of the pond to really judge. I simply find it peculiar and
suspect there's something else involved in the problem, if there really
is a problem.
>>> "William Davies" <bill@rarebits4classics.co.uk> 07/23/03 12:08PM
>>>
Most of the other vehicles I've seen with similar downpipe arrangements
use 4 fixing studs rather than the Spitfire's 3. The rigid exhaust
mounting at the bellhousing certainly doesn't help, as it forms a
convenient fulcrum point, with the exhaust acting as a lever between the
manifold and the rear exhaust mounts. I have improved (but I would
hesitate to say cured) the exhaust blowing problem by removing the
mounting at the bellhousing. This allows the exhaust to hang freely with
less leverage being exerted at the joint as the engine moves on it's
mountings. The problem is too common (in my opinion) to be down to face
matching. Those downpipes and manifolds I've examined on the bench have
certainly been correctly aligned in all respects with good face-to-face
characteristics,
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