Thread:

How do I tune an adjustable vacuum advance

My HEI distributer has an adjustable vacuum advance canister that allows me to adjust when it starts advancing (I guess, more accurately, retarding). I lost the instructions and can't seem so get any solid info searching the internet.

I seem to remember something about making sure it is set so that it's fully advanced 1-2 inches of vacuum less than idle vacuum, to insure it's consistently fully advanced at idle.

Is this correct? Anything else?

I seem to be x-tra full of hot air latley so...If you must run a vac adv, how bout make the diaphram stiff so it takes alot of vac. to move the rectifier or what ever . Then shoot it for you total # which is a whole nother thread I was going to say start with 35*. I would think if that was set loosly you'd let off the gas and you'd be at 50*. My just my 02. Figured you guys could use a good laugph. lol btw what was this going in again? max r's ect?

stick an allen in the vacume hole, trial and error

Originally Posted by H20MOFO

...btw what was this going in again? max r's ect?

18' flat v-drive, 396 BBC, it's only turning 4700-5000, I think it has 18 gears, and I'm turning a 12x14 3 blade

I think most would say lock the vac deal out. Having said that I had V-drive, with an olds that would beat the piss outta ya at 4500 r's, and it ran fine with a stock vac adv hei. couldn't help much with timing, I would think your concern should be your total #'s , and like HD, I mean Sanger guy said, try it out of the box check some #'s turn it 1 way well you get it. On an Hei is the vac port on the carb suposed to come from above, or below the throttle blades, I think above and I f'd that up once on a street motor.

Originally Posted by H20MOFO

I think most would say lock the vac deal out. Having said that I had V-drive, with an olds that would beat the piss outta ya at 4500 r's, and it ran fine with a stock vac adv hei. couldn't help much with timing, I would think your concern should be your total #'s , and like HD, I mean Sanger guy said, try it out of the box check some #'s turn it 1 way well you get it. On an Hei is the vac port on the carb suposed to come from above, or below the throttle blades, I think above and I f'd that up once on a street motor.

This is a dangerous crowd to start any conversation about the where why and hows of vacuum advance. I've done quite a bit of research and am confident once it's all dialed in I'll be happy with it.

?

Originally Posted by Budweiser

This is a dangerous crowd to start any conversation about the where why and hows of vacuum advance. I've done quite a bit of research and am confident once it's all dialed in I'll be happy with it.

I am pretty sure that the adjustment is just to set the rpm the advance starts. You also have the mech advance. Best way is to run the boat with a light on it. Rev it up till it stops advancing, see where your at and advance or retard as necessary. Most of the aftermarket distributors start you out at about 10-12 deg to get you into the 34-38 degree total. Its one of those things were your going to have to put on the light and see whats happening.

Sorry,I guess? was it cause I was messin with HD cause that's fun. Seriously ,I'll stop, or shut up or? Btw both you and 2 sav need to adopt your so-cal names. Shit I should shut up.

I can't blame it on that yet.

Vac advance and performance aren't usually mentioned in the same sentence. I am however confident that some one can prove me wrong. lol
Edit. fwiw I'm outta this thread, wasn't trying to piss any one off.

It's cool H2o, I'm used to it, thot i was under cover over here

My bad