When you get the Holley book, Sit down and read it. Understanding what each circuit of the carb does (or doesn`t do) will help you understand everything alot more clearly. That will help you to understand how to tune each circuit of the carb alot better. Vacuum advance is used to increase the timing advance at cruise speeds to help gas milage... It is not really a part of of the performance side of the carb. If you hook a vacuum guage to your intake and rev the engine you will see the vacuum Drop when you crack open the throttle. The vacuume advance doesn`t do any thing at that point due to Low vacuum. if you gradually increase the rpms and then level the engine off at cruise R.P.M. (say maybe 2,200 ) you will see the an INCREASE on the guage of vacuum...thus pulling in the extra timing that would be needed while cruising to help increase gas milage.
From past experience before i have found that with the vacume advance hooked up i've had driveability problems with a big cam.You know the feeling when it doesn't seem just right.Took off the advance set total timing and bingo it runs like it should.I've seen more probems in a performance engine with the vacume advance since too.
Vacuum advance won't give you any real power but it will give you gas mileage. Use that vacuum advance.
Agreed ..But if you are only going to drive the car a thousand Miles (as you stated on page 2 of this thread) a year Scooper you might want to just cap it off and let it be one less thing to worry about.
Sorry guys, went to bed and didn't stay involved with this last night... Here is the experience I have had with vacuum advance... My old edelbrock had 2 nipples, one had vacuum at idle, the other didn't. When I hooked that old engine up to the one with full-time vacuum, it idled higher, of course, but it also was WAY more responsive when taking off (what I am calling the "kick in the pants"). I kicked the idle back down and it was timed INITIALLY at about 32-36. Of course, it felt no different at high speed, it was running the same vacuum it would have been on the other nipple by then. I always ran it on the non-vacuumed nipple just because it didn't seem "right" to have 32-36 degrees initial timing. And at that time, I thought it might have been part of the overheating issue (remember that issue, back in 2005 or 2006?). I guess that "kick" I felt when I "thought" the timing was kicking in was just the beginning of my power band where it finally got a little "oompf" and really started to accelerate. You can hear it in my audio clip of my new exhaust...it takes off kinda slow and then hits around 2500 rpm and then really starts to accelerate like it has a little power.
I am not sure what the kick in your pants is cause vacuum advance goes to zero at wide open throttle. Vacuum advance is strictly an economy device. Its only purpose is to save gas! Your mechanical advance is where you can see performance gains. you can get a performance curve by changing weights or springs on the centrifugal advance plate.
Thanks!!! I am at the public library and was looking through the stacks...I found that Chiltons has a Holley book. Anyone ever taken a look at it? I would like to see or hear if it is worth ordering. Library does not have it, but I found reference to it in the back cover of another book.
Here you go Gene... When I get the book, i need to also figure out what that is on the pass side that is leaking...
