> Before I put a heat shield on my TR4 vintage racer, the domes on the carbs
> we VERY hot to the touch. When I hand fabricated the heat shield and
> installed
> it, the domes actually became cool to the touch.
WHich brings up a point that people should perhaps be aware of. Carburetors
actually need a certain amount of heat to work properly under all conditions, as
the pressure drop at the butterfly under cruise conditions causes a
refrigeration effect. Under just the right conditions, the cooling can form ice
(known as carburetor icing) which makes the engine run like crap.
I've never had this happen on a TR, but it did happen to me once on an Audi
100LS where I had disconnected the original carburetor heat (for the same reason
we are adding heat shields). And I have seen condensation form on the SUs on my
TR3A, due to the chilling effect.
I'm definitely NOT suggesting that the heat shields are a bad idea, just that
people should be aware that keeping them cooler also introduces the chance of
carburetor icing. If you're driving along on a cool evening (the kind that
isn't below freezing but leaves ice on the grass in the morning) and your engine
suddenly starts running like a bucket of bolts, you'll have one more potential
reason why.
Icing is very rarely a problem on the race track of course.
Randall
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