How much advance........

[rgp266]

is there in a '87 Small Block Distributor Mechanical advance plate? I have heard everything from 20° to 25° all the way up to 34° because of the ported vacuum set-up. Is there a differance in the vacuum canister older verses newer? Can that '87 Distributor be re-programmed (I.E. changing the weights and springs on the advance plate) to early, pre-emissions. settings? Is there a vacuum canister for the Small Block Distributor that will fully deploy at a lower vacuum, something on the order of 8" HG?
Bob

 

[67Dart273]

There are several differnt vacuum cans, so far as I know they will interchange

Even as new as an 87 is, you should find out "what it is" and not "what it is supposed to be," IE it could have been replaced at some point.

Many of the mechanical assemblies are stamped on the bottom in distributor degrees (x2 for crank degrees) but it's on the bottom, so you have to pull the advance apart to see. If you have a caliper you can get "down in" one of the slots, you can get an idea by measuring the slot

Modifying advance slots
degrees / slot size
6.............. .340
7................355
8................375
9................390
10...............405
11.5 ...........420
12...............435
13...............445
14...............460
15...............475
16...............490
17...............505
18...............520