Advance Curve

[Bud]

You want somewhere around 30 to 32 degrees of advance with only the centrifugal advance functioning The vacuum advance should only come in at part throttle and not at idle or wide open throttle. The vacuum advance should give you somewhere around 13 to 15 degrees of advance at 13 inches of vacuum. It sounds like you do not have enough centrifugal advance which would cause you to have sluggish acceleration. If you remove the stop bushing it might give you a bit more advance. Bud

[Kato]

You want somewhere around 30 to 32 degrees of advance with only the centrifugal advance functioning The vacuum advance should only come in at part throttle and not at idle or wide open throttle. The vacuum advance should give you somewhere around 13 to 15 degrees of advance at 13 inches of vacuum. It sounds like you do not have enough centrifugal advance which would cause you to have sluggish acceleration. If you remove the stop bushing it might give you a bit more advance. Bud

I was thinking that very thing. I'll give that a try. Thanks for all of the great advice!

[bensherb]

You want somewhere around 30 to 32 degrees of advance with only the centrifugal advance functioning The vacuum advance should only come in at part throttle and not at idle or wide open throttle. The vacuum advance should give you somewhere around 13 to 15 degrees of advance at 13 inches of vacuum. It sounds like you do not have enough centrifugal advance which would cause you to have sluggish acceleration. If you remove the stop bushing it might give you a bit more advance. Bud

The only distributors I've encountered that can give that much mechanical advance were those that had no provision for a vacuum opperated timing modifier. The ones with vacuum cans got most of their advance from vacuum.

[Bud]

A stock Delco or Prestolite distributor used in a non R 259-289 should have 24 degrees plus or minus a couple of degrees centrifugal advance at 2400 engine rpm and that spec is in the shop manual. I own a working distributor machine and and those numbers are what I see with a distributor that is in good condition. With a base timing of 4 degrees BTDC, that will give you 28 degrees at the crank at 2400 rpm with the vacuum advance disconnected. That gives a good safety margin for detonation for differing quality of fuel and operating conditions. I have R1 spec distributors that have 20 degrees centrifugal advance in my Avanti and in my 62 Hawk that has flat top pistons and an R3 cam, so I usually set the base timing at 10 degrees BTDC which gives me 30 degrees of advance at the crank. With those numbers, I don't have problems with detonation. Much more advance than that, I have had detonation problems especially in warm weather which I have right now here in Kingman, AZ. Bud

[JoeHall]

I was just in the garage playing with the 63GT, which has HFI and computer controlled spark. Per dial-back timing light, at hot idle (750-800 RPM) it is at 29-30 degrees; at light throttle (high vacuum) and 1800 RPM it is 40-41 degrees; at light throttle, 2800 and up, it is 42-43 degrees. Of course If I dump it, at any RPM, manifold vacuum drops temporarily, which retards timing maybe 15-20 degrees; it picks back up so fast I cannot measure it, can only estimate.

So when cruising, light throttle and at high vacuum, it likely runs around 38-43 degrees. Anytime the motor lugs and drops vacuum significantly, maybe below 10", timing retards as much as 15-20 degrees. I had Bill Hamilton set the chip up to mimic the advance curve in the 59-64 Shop Manual for early Delco distributors, and he pretty much nailed it. I could not ask for a sweeter running 289, under all conditions, hot/cold, fast/slow, etc.. The 62GT runs the same, since it also has same HFI. Only difference between the two cars is the 62 is 3/OD, and the 63 is 700R/AOD.