The response to my original plea was very helpful and I thank you one and all.
The net result seems to be the offset in the manifold. The manifold must drop
downward so the the carb can sit low enough to clear the hood. As several people
have pointed out, the problem is known, if not common, as you have seen hoods
with outward dents where the air filter has hit the hood. But many other people
have had no problems.
At first I thought it may be the Cannon manifold I have. Paul Tegler, for
example, used the Pierce manifold that appears to have more offset than the
Cannon. But others have reported successful installations using Cannon. I then
contacted Pierce for a replacement manifold and learned that indeed the Pierce
has more offset, by about 1/4". I don't think that is enough. It looks like I
need about another 3/4" to safely clear the air filter. At the very minimum,
maybe 1/2" would do it.
So there appears to be some other factor at play here. As someone mentioned,
motor mounts may be a factor by raising the engine higher than others. Maybe the
hood position is a factor but mine is very typical as compared to other Spits I
know.
But I'm not giving up on a possible difference in manifold offset. If you could
measure the offset of your manifold, the make, and model number of the manifold,
it could help to confirm whether this is a factor. I need to know how much the
top of the tubes drop from the engine end of the manifold to the carb end, as
measure on the tube not the mounting flanges. The make/model may be on the
manifold casting (mine says Cannon and a four digit number).
Even better, if you have solved this problem, I would love (as would many others
with dented hoods) to hear your solution.
Vic Whitmore
76 Spitfire
Thornhill, Ontario
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