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Vacum Advance

Posted: Tue Oct 26, 2004 8:31 am
by Thonger
Another stupid question, from the king of "i don't know about petrols".
The vacum advance on the dissy, on mine has one hose running to it, from the holly. With the pipe on the reverse side, should that have a tube attached?, blocked off? or left open to equalise.

Posted: Tue Oct 26, 2004 11:52 am
by Thonger
Also checked the timing last night, was at 12deg btdc, I know that some guys are running this for gas and on premium, but I only run regular. The manual says 5deg atdc for 92 octane and 8deg for 85, Buggered if I know what I should set it too. Also any tips on matching the timing with the dwell, as i changed dwell it changed timing also, along with the idle speed changing. Is it just a case of fiddleing around till all 3 match? any tips?

Its a 78 rangie with a holley carb.

Posted: Tue Oct 26, 2004 7:04 pm
by J Top
The second pipe on the vacuum advance unit is a pollution control device called a vacuum retard.Just leave it open to air as with a different carb it is superfluous. Crankshaft pulleys are also vibration dampners with a rubber sleeve between the hub ,which is keyed to the crank ,and the outer pulley with the timing marks,and as the pulley ages it is not uncommon for the timing marks to "walk" arround the pulley, meaning if you use them your timing will be retarded.
The moment you start your engine after fitting new points it starts to go out of tune,your best bet would be to see what the guys here recommend as the best aftermarket electronic ignition.A lot of people fit the HEI dist out of a Chev/GM which gives an excellent spark and is a cheap fit.
J Top