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Old 09-17-2008, 10:43 AM
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Throttle Bore Matching

The reason I'm sending this diagram is because we were trying to help a guy - and found that he had mounted a "too big" carb on a smaller manifold (one hole over another) - and simply added gaskets under the carb to get the butterflies to swing. This is only OK to drive it home from grandma's house.

This is a double problem - the step all around the bore is bad news for air flow all in itself - but also the primary butterfly turns down and then starts to "reseal" at the rear. This forms a "pocket" where air flow is nearly stopped - and everything has to go over the leading edge of the throttle blade. It is also happening at a throttle opening where you should just be reaching "cruise" for ordinary driving.

Charlies "B" manifold was opened to create a slot - which is a very common practice with aluminum high perf replacement manifolds. Makes a big hole right where the butterfly swings open under the carb. It is also a lot cheaper than buying a "BlueThunder" Y-block manifold.

Last edited by GREENBIRD56; 09-17-2008 at 10:45 AM. Reason: missed word
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