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| Re: Vacuum Advance [message #66140 is a reply to message #65952] |
Mon, 30 November 2009 16:32   |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma:
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Well I've kept quiet for a long time. Under light or no loads these engines will tolerate a lot of advance with no adverse effect. Under any application of load, you want the timing to retard--both schemes will do that if you are above the idle range. The main difference will be at idle and just above. Manifold vacuum will be at 18 to 20", ported will be around 0. That means with manifold vacuum, you will have whatever advance the can will give it. Unless your engine is extremely hot, you won't get pinging at those low engine speeds. As the throttle opens, the vacuum advance curves will come together and act the same way--light load: high vacuum advance; heavy throttle, minimal vacuum advance. What you don't want is high vacuum advance under load--neither configuration will give you that. It is true that manifold vacuum will significantly increase idle speed. I have seen a couple of engines where the idle speed screw could not be backed off enough. The static advance should not be backed off or you will decrease advance across the board. It also seems that the 403's are more tolerant of high advance across the full range. Regardless, I know some of us run manifold with great results, and others are just as happy the other way and frankly it's not that big a deal!
Bob de Kruyff
78 Eleganza
Chandler, AZ
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Vacuum Advance
By: jwillard on Sat, 28 November 2009 12:46 |
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Re: Vacuum Advance
By: rgleas on Sat, 28 November 2009 12:58 |
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Re: Vacuum Advance
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Re: Vacuum Advance
By: rgleas on Sat, 28 November 2009 14:38 |
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Re: [GMCnet] Vacuum Advance
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Re: [GMCnet] Vacuum Advance
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Re: [GMCnet] Vacuum Advance
By: jwillard on Sat, 28 November 2009 17:51 |
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Re: [GMCnet] Vacuum Advance
By: dmumert on Sat, 28 November 2009 18:22 |
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Re: [GMCnet] Vacuum Advance
By: rgleas on Sat, 28 November 2009 20:06 |
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Re: [GMCnet] Vacuum Advance
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Re: [GMCnet] Vacuum Advance
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Re: Vacuum Advance
By: rgleas on Sat, 28 November 2009 17:37 |
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Re: Vacuum Advance
By: JohnL455 on Sat, 28 November 2009 18:57 |
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Re: Vacuum Advance
By: JohnL455 on Sun, 29 November 2009 08:09 |
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Re: Vacuum Advance
By: rgleas on Sun, 29 November 2009 08:25 |
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Re: Vacuum Advance
By: mdryan on Sun, 29 November 2009 08:31 |
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Re: Vacuum Advance
By: jwillard on Sun, 29 November 2009 09:56 |
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Re: Vacuum Advance
By: roy1 on Sun, 29 November 2009 19:04 |
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Re: [GMCnet] Vacuum Advance
By: USAussie on Mon, 30 November 2009 01:01 |
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Re: [GMCnet] Vacuum Advance
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Re: [GMCnet] Vacuum Advance
By: ljdavick on Mon, 30 November 2009 19:07 |
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Re: [GMCnet] Vacuum Advance
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Re: Vacuum Advance
By: mdryan on Mon, 30 November 2009 08:01 |
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Re: [GMCnet] Vacuum Advance
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Re: [GMCnet] Barbie GMC on eBay (#140362019346)
By: k2gkk on Sun, 29 November 2009 11:06 |
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Re: [GMCnet] Vacuum Advance
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Re: Vacuum Advance
By: fred v on Sun, 29 November 2009 14:23 |
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Re: Vacuum Advance
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Re: Vacuum Advance
By: Mike_H on Sat, 12 October 2019 10:21 |
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