Small block distributor timing??

[dustoff440]

The Distributor I have is set up for 34 degrees total advance WITHOUT the vacuum advance which is marked 8.5 degrees Do I double the 8.5 for TOTAL advance or just add 8.5.

The engine is basically a stock 360 Magnum with a knock off air gap, .500 lift 276/286 duration lift cam on a 112.5 centerline, Thermoquad, 340 Exhaust manifolds, 2000 stall converter and 3.23 gears in a Dart that weighs 3450 with me in it.

 

[67Dart273]

Make sure you have your numbers straight. There are several variables

First of course is your initial timing.

Second is the mechanical advance, and it can come in sooner or later, and with certain springs, can lag and not be "all in" until some fairly high RPM

Last is the Vacuum advance.

FULL THROTTLE you do not figure the vacuum advance, because when you mash your big no12 down, the vacuum goes away. So just initial added to mechanical is for "power"

for mileage/ cruise, IF IF IF the mechanical is all in by highway cruise (might not be depending on springs) then you have

Intitial + mechanical + vacuum, all added together.

But this "cruise" total can be up into the 50's degrees

 

[fishy68]

What he said. And for the vacuum advance, that only comes in at light throttle like 67Dart said it's double the number stamped on the can. So if you have 34 degrees total (initial and centrifugal combined) you add 17 more (8.5 times 2) to that when the vacuum advance is in for a total of 51 degrees at part throttle cruise.