I am putting in a new vac. adv.(the old one was torn & leaking). The directions say to use the same number of turns from the seat as the old one(the allen screw in the primary vac port), but the old one was bad and had been mis-adjusted i.e it was all the way down on the seat. So what should I set it at? It is the small vac.adv.. I know there are 3 dif. kinds. What is the dif.?
Actually the directions are kind of idiotic since many different spring rates and types were used in the old days. If you have a vac gage and pump you can make the settings yourself. One of those hand pumps will do the trick. Getting it close is about all you can do with a generic adjustable vacuum unit.
1971 distributor & engine specifications for the 400 without EGR:
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This was the GOOD year for the 400 engine before it was smogged to death.
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Distributor part #D00F-U
Centrifugal Advance Start: 0-0.5° @ 350RPM Finish: 14° @ 2275RPM
Vacuum Advance Start: 0-1° @ 5" Finish: 12.5° @ 25"
Point Dwell: 26-31°
Initial Timing: 10° BTDC, 6°BTDC California.
Vacuum given in inches of Mercury (Hg).
RPM specified as distributor RPM.
Degrees specified as distributor degrees.
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Double those values for crankshaft figures:
Example: 0-0.5° @ 350RPM distributor becomes 0-1° @ 700RPM on the engine.
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You can use a timing light. observe your timing with the vac. hose connected then pull it off. The difference is your vacuum advance. Just adjust for 10 to 12 degrees and see how it feels.
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vac. adv.
