 HEY V8ers Carb/Distributor Q, Which vacuum port? |
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| marks914 |
 Apr 29 2006, 11:19 AM
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#1
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Senior Member  Group: Members Posts: 845 Joined: 9-October 04 From: the motor city Member No.: 2,912 Region Association: None  |
Just was swapping out the Holley double pumper for an Edelbrock unit.
I can never remember which vacuum port to connect the distributor vacuum advance to. Timed or manifold? Its a 78 Chevy 305, stock HEI with no EGR. Any help appreciated, I guess its a 50-50 shot. Thanks Mark |
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| messix |
Apr 29 2006, 11:37 AM
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AKA "CLUTCH KILLER"! Group: Members Posts: 6,995 Joined: 14-April 05 From: between shit kickers and pinky lifters/ puget sound wa.north of Seattle south of Canada Member No.: 3,931 Region Association: Pacific Northwest |
timed
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| marks914 |
Apr 29 2006, 11:42 AM
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Senior Member Group: Members Posts: 845 Joined: 9-October 04 From: the motor city Member No.: 2,912 Region Association: None |
Thanks!
I'll be running in a few. Mark |
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| nick mironov |
Apr 29 2006, 11:43 AM
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#4
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nickm Group: Members Posts: 204 Joined: 12-June 05 From: San Francisco, CA Member No.: 4,264 |
I have a Holley 4-barrel and I use the metered vacuum port (no vaccum advance at idle). If you use manifold vacuum, you will get vacuum advance at idle. It seems that people are split over which one is best and experimentation with both is recommended.
It seems to me that the selection of metered vs. maniflod vacuum would also be dependant on the overall ignition advance you are using. I also have a stock GM HEI and have 11 degrees if initial advance, 20 degree mechanical advance with medium springs that are all ib by 3,000 rpm, and the adjustment on the vacuum advance canister is set at about mid-point. I have not experimented much with other combinations, but plan to do so. What is your advance curve like? Nick |
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| marks914 |
Apr 29 2006, 12:10 PM
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#5
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Senior Member Group: Members Posts: 845 Joined: 9-October 04 From: the motor city Member No.: 2,912 Region Association: None |
QUOTE(nick mironov @ Apr 29 2006, 09:43 AM)  I have a Holley 4-barrel and I use the metered vacuum port (no vaccum advance at idle). If you use manifold vacuum, you will get vacuum advance at idle. It seems that people are split over which one is best and experimentation with both is recommended. It seems to me that the selection of metered vs. maniflod vacuum would also be dependant on the overall ignition advance you are using. I also have a stock GM HEI and have 11 degrees if initial advance, 20 degree mechanical advance with medium springs that are all ib by 3,000 rpm, and the adjustment on the vacuum advance canister is set at about mid-point. I have not experimented much with other combinations, but plan to do so. What is your advance curve like? Nick I thought it was timed vacuum. My advance is bone stock, whatever that is; with a touch of twist the dizzy until it knocks and then back a bit. Mark |
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