i have the mechanical advance of slantsix dist and the vac advance of a bb dist, i got it working but i was wondering if anybody try this and is there a way to slow the vacum from coming on at low rpms. with the idling at 1200rpms timing is set at 10degs, bring rpms up to 2500rpms mech adv is all in at 25degs,as soon as i increase rpms above 3000rpms the vac timing pulls timing back to 10degs. i know i can limit the amount of timing taken out by restricting the amount of travel of the magnetic pickup plate. i have 20lbs vac at port fitting on carb but that is only holding throttle open in park. the vac canster is adjusted all the way back to slow it as much as i can. i cant drive on the road here and the track is over 100miles away. any help please

This list of vacuum advance units might help you get where you want to be.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Terry,

If this is a race only car, why do you run vacuum advance at all?

Lou

_________________
Home of Slant6-powered fun machines since 1988

A good first step would be to get the mechanical advance working. Just disconnect and plug the vacuum line while you work out the mechanical advance. Race cars don't need vacuum advance (like Lou said) but it would help fuel mileage a bit on the drive to the track.

A good basic start would be like this:

Disconnect vacuum line,
Set the total timing to 30 degrees as 3000 rpm with a dial back timing light.

This might give you lots of advance at idle, but that can be O.K. for a race car. If you have problems with too much advance at idle, then you must recurve.

As for getting the vacuum advance working, you should have the vacuum line connected to PORTED vacuum, not manifold vacuum. Where is the connection?

_________________
1980 Aspen 225 super six

sorry for the confusion, this is something i am trying for my race car, 2yrs ago i built a 0.080 over 318 valve 8.9/1 comp. 556 lift/306dur cam, with a 4-71 blower and two 600 cfm holleys, the problem is off the line through second, car runs great, 1.57et 60fts,7.42et 1/8 mile, but when i hit third the car seem to go super lean (burnt plugs and head gaskets) i have made great improvements ,the last weekend never had any signs of detination but the cam bearing spun and hurt the rockers and push rod. while i had everything apart cleaned up back together and running know i what to build a distributor that will have mechanical adv to 25deg total , which i have but retard the timming around 5degs when boost comes on.i have modified a 440bb pickup coil plate to fit a slantsix distributor, it works but it pull out to much timing and at to low an rpm. the motor idles at 1200 with 10degs at 2500rpms the mech is all in at 25degs, now with vac line hooked up at 3000rpm 20lbs vac it pulls timing back to 10degs. i was just wondering has anyone tried this and does anyone have any ideas on how i can slow the vacum can so it will pull timing back at a higher rpm. the amount of timing doesnt seem to be a problem all i have to do is restrict the amount of travel in the puckup coil plate. were this is a full tube chassis car the only place i can drive it is at the track so any tip or ideas would be appreciate.