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Or Seth, either one
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Discussion Starter #1
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?
 

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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?
 

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Or Seth, either one
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Discussion Starter #4
...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
 

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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.
 

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Or Seth, either one
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Discussion Starter #6 (Edited)
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.
 

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Cantard
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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.
 

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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.:D Shit I should shut up.:)grn:)sphss:)devil
 

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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.
 

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Or Seth, either one
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Discussion Starter #16 (Edited)
Lock it............you'll be doing your engine a favor!! ;)
I was afraid this would come up. :)

As much as I want to stay away from the "how why and when" of vacuum advance (really just looking for a solid answer to the question), I still have to (regrettably) ask...

Why?


I realize this opens a large debate. Probably good reading to have in the archives here. But still, if anyone knows the answer to the original question, please let me know
:D
 

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Or Seth, either one
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Discussion Starter #17
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.:D Shit I should shut up.:)grn:)sphss:)devil
No reason to apologize. Maybe I should use those smiley things more often.
 

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steelcomp was here
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My understanding of vac advance is that at part throttle cruising or no throttle (idle) the vac will advance the timing beyond where it would normally run, mainly for better emissions. Why do you want this in a boat? It really has no performance purpose. If it's a jet, lock your dist at the full amount of advance you're going to run and be done with it. If it's a prop, run as much initial timing as you can and have the rest in by 2500 rpm.
 

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On many performance cars I like to adjust the vaccum pot so it doesn't add any advance around 10"hg. SOme differ of course. When you get under 10"Hg you are usually under quite a load and do not want any additional advance over and above what the dist gives you.

On boats, you are usually under too much of a load at cruise rpm to use vacuum advance. IE: lots of timing and load are no good !

Vacuum advance is for better light or super light load - ie: cruise on 4 wheels on a highway - for fuel economy during cruise as is leaner A/F ratios.

High vacuum and very little cylinder fill takes a while to combust. Thus the extra timing needed. You only get high vaccum, again, when cruising on wheels.

That's the generics.

When you remove/disconnect the vaccum advance mechanism make sure you make that part of the distributor not able to move and add/subtract timing on it's own.
 
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