vacuum advance
- Thread starter moparguy
- Start date
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GoodysGotaCuda
Mr. Goody
nope, the full manifold vacuum port probably will. from what i understand ported should not.
Sanguine
Well-Known Member
NO...a ported vacuum nipple should have no vacuum at idle, unless you have the idle cranked up way too far to compensate for a large cam, in which case you need to modify the carb
more info may be helpful
more info may be helpful
It's a 400 bored .040 over, fairly mild cam (comp xe cam 224/230 lift at 050 inch lift with 477/480 lift) 750 cfm holley, did change secondary spring, main jets, and power valve. I reused the gaskets. Should I have put a new gasket behind the metering block? Also shaved heads and weiand dual plane intake. Idles around 1000 in park and 500 in drive. If It is not supposed to pull vacuum at idle, do you really need to disconnect it when setting your initial timing?
lead69
hopeless car junkie
Just to cover the basics but are you sure your running to a ported source and not from the carb base,the vaccum ports on the carb base pull full vaccum.Also you do need to disconnect the vaccum advance at idle to get a true reading of your base timing.You can run the advance to full vaccum at idle but you will need to restrict/limit it so you dont have too much timing or an erratic idle.Running this way smoothes the idle with a large cam,gives better driveability and runs cooler while idling but probaly isnt neccesary with your cam.
C130 Chief
Mechanical Genius
If your throttle blades are open slightly at idle, the advance port may be getting a signal. There are a couple ways to correct this (assuming you aren't content to just live with it). Many Holley carbs have a secondary throttle plate stop screw, so you can crack the secondaries slightly allowing the primaries to be a little more closed removing vacuum signal from the advance port. The other way is to drill small holes in the primary throttle blades. If you go this route start small like 3/32". A lot of smog era OEM carbs went this route.
Also, most Holleys have their ported vaccum nipple on the right side of the primary metering block. If you have a 3310, you should have the secondary idle stop screw located onthe underside of the throttle body (or at leastt he older ones did.)
Also, most Holleys have their ported vaccum nipple on the right side of the primary metering block. If you have a 3310, you should have the secondary idle stop screw located onthe underside of the throttle body (or at leastt he older ones did.)
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