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Old 09-08-2016, 04:55 PM   #31
davepl
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Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
Re: Idle vacuum - why only 10 inches?

Quote:
Originally Posted by geezer#99 View Post
What carb?
What's your timing curve like?
Have you confirmed #1tdc with the timing tab?
Original Q-jet, rebuilt by a Q-jet shop. The only "wait a minute" moment I can think of on the carb is when they were dynoing it they wanted to increase the rear jet size, did not have one, and so they drilled it out to the specified size. It fixed the fuel curve but could a secondary jet "leak" extra fuel or something? It's a long shot, I'm just trying to include all of the info.

Curve is stock, but I'm running 12-15 degrees initial to get as much vacuum as possible. But at this point I'm not even looking at the timing tab, just maximizing vacuum as best I can by increasing advance until more's not better.

Not sure what you mean by confirming #1 TDC - like center it with a piston stop? In what scenario would it be wrong, mis-ground gearset or cam? I wonder if the timing tab has the accuracy/resolution to show me. I guess even 2 degrees off would raise suspicion, but let me know what you'd like me to check.
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