Reply to "Vacuum"

Marlin & Mark,

from what I'm reading it sounds as though the 292H is a lumpy idle, high overlap type cam, but I'm not convinced 5" vacuum is the best you can do. Loosen your distributor clamping bolt & slowly twist the distributor in the advance direction until you find the spot where it idles the fastest, that will also be the spot where the highest intake manifold vacuum is achieved. Ignore anything you've ever been told before, that setting is the ideal static advance setting for your motor.

IF 5" vacuum is all the vacuum your motor can muster up, then forget about running a PCV valve, and forget about running vacuum advance on the distributor; ported, manifold, whatever.

I hate power valves! lol. They are the crudest device ever installed on an automobile! What was Smokey thinking when he included that in the design? I think Smokey was smokin' them cigarettes you don't buy at the store, know what I mean?

I want to make 2 points regarding setting a Holley carb (I've never worked on a Demon yet, but I'll bet this applies to them as well). (1) The power valve should only open at full throttle, so monitor your manifold vacuum while driving the car with the pedal mashed, and install a powervalve that opens at that vacuum. The power valve should never open during part throttle operation. (2) The idle stops for the secondary butterflies should be set so that at idle the small idle transfer slots in the bore are partially exposed below the butterflies. If the secondary butterflies are too far closed, this will force the primaries too be opened too far & the car will not idle properly.

The upper picture shows the secondary butterfly set properly, you can see the transfer slot exposed near the tip of the screwdriver, the lower picture the butterflies are set too far closed, the transfer slot is concealed.

I would appreciate feedback on the results, especially concerning the manifold vacuum.

Your friend on the DTBB, George