Its a game you play. The object is to get the
maximum vacuum with the idle screw out the
least way. A good engine with normal cam
should have 18-20 psi vacuum or more and
the needle should not fluctuate.
You work each idle screw separately. If you
screw it all the way in, you should notice the
engine rpm drop and run rough. Start screwing
it out and the rpm will pick up and the engine
will smooth out. Eventually you will get to a
point where continuing to turn the screw out
will no longer have any effect. You've gone to
far in that case.
Remember the object of the game. Maxim
vacuum with the screw the least way out. Don't
be surprised if you have to reset the idle speed
down while doing this. With one Tiger I adjusted
where started at 650 rpm and when done the
idle was 900 rpm. A quick idle adjustment
fixed that. Is amazing to some that a V8 will
idle just fine at 650 rpm. But a stock engine
with stock cam was meant to do that.
1 1/2 turns should put you in the neighborhood.
Once down, the Tiger should purr like a cat.
Dave Johnson
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