mech advance or vacuum advance?

LX XLR8R · 02-04-2002, 11:58 AM

swaping to car..combo is in sig..im learning as i go

...so what is better and why?what are the advantages of using a MSD mechanical advance as oposed to an 85 distrubter?

and what is the diffrence between points and elctronic?i am carbed illiterate..im too young(23) to know that stuff..i grew up with EFI

Coupe Devil · 02-04-2002, 01:21 PM

You and I are in the same boat. I am soon to be 23 and also grew up with EFI. I did a 300 6 cyl to 302 swap in a truck I had and went carb but nothing performance just stock replacement stuff. The drag motor is carbed and my guru here suggested I go vacuum adavance know because of my level of knowledge, affordability, and ease of work. I am going to use a MSD 6AL box. Good thin about that is it can be used with either distrubutor. I got a 85 dist at the parts store for $85 with cap rotor and base. Not to bad a price I think. I would suggest the vacuum advance due to availibilty and ease of operation. I understand wanting optimum performance but I dont want to buy parts that wont benefit me yet if I dont have to.

Brad

red82gt · 02-04-2002, 05:19 PM

Vacuum is better for a street car, when cruising at part throttle the timing doesn't advance so you'll get better fuel economy and at part throttle acceleration the curve will advance faster from the change in vacuum, whereas a mechanical advance is controlled by the engine rpm.

For a drag car that doesn't need fuel economy, driveability or part throttle response and spends most of it's time at full advance (3000+ RPM) then mechanical is the way to go.

If you do go with vacuum advance, find someone who knows how to re-curve distributors, it's becoming a lost art but it makes a big difference.

BTW I'm only 24 and since the mustang mags don't talk much about carb tuning (except for some full blown race motors) I've learned a lot from HOT ROD and from other books about tuning carbs.

PKRWUD · 02-06-2002, 01:30 AM

I have never seen a distributor that had vacuum advance, and did not also have mechanical advance. If you are asking if you should just use mechanical advance as opposed to using both, it depends on what you want to use the engine for. If you are building an everyday driver, I would recommend using both. If you are building a weekend only racer, i'd just use mechanical.

Take care,
-Chris

David Fulford · 02-06-2002, 12:42 PM

Is there an exact science or science at all for changing the springs that are in the MSD distributors for altering the mechanical advance. I just stuck the distributor(MSD8582)in as it came. I have several other springs and what not. Would I really get any noticeable performance gains from messing with it a bit?

PKRWUD · 02-06-2002, 02:53 PM

Yeah, there is a science to it, actually. The lighter springs allow the full advance to be acheived earlier, whereas the heavier springs put the full advance off until a much higher rpm. When you want the advance to reach full depends on everything else, like your gears, your other engine mods, etc.

Take care,
-Chris

David Fulford · 02-06-2002, 03:13 PM

Makes sense. Thanks! I guess I will play with it a bit and see what happens. Although knowing me I'll screw something up. Later.

02-04-2002, 11:58 AM	#1
LX XLR8R Dirk Diggler Join Date: Feb 1999 Location: SLOATSBURG, NY Posts: 1,931	mech advance or vacuum advance? swaping to car..combo is in sig..im learning as i go ...so what is better and why?what are the advantages of using a MSD mechanical advance as oposed to an 85 distrubter? and what is the diffrence between points and elctronic?i am carbed illiterate..im too young(23) to know that stuff..i grew up with EFI __________________ 95 undecided cubes, AFR 185s,undecided cam, undecided intake, and a 150 hit 89 "turbonotch" 2.3T You might want to hold on..i saw this on a cartoon once

02-04-2002, 01:21 PM	#2
Coupe Devil Moderator Join Date: Mar 2001 Location: Myrtle Beach SC Posts: 1,643	You and I are in the same boat. I am soon to be 23 and also grew up with EFI. I did a 300 6 cyl to 302 swap in a truck I had and went carb but nothing performance just stock replacement stuff. The drag motor is carbed and my guru here suggested I go vacuum adavance know because of my level of knowledge, affordability, and ease of work. I am going to use a MSD 6AL box. Good thin about that is it can be used with either distrubutor. I got a 85 dist at the parts store for $85 with cap rotor and base. Not to bad a price I think. I would suggest the vacuum advance due to availibilty and ease of operation. I understand wanting optimum performance but I dont want to buy parts that wont benefit me yet if I dont have to. Brad __________________ 1990 GT, 347, TFS TW Heads, TFS Cam, TFS Track heat, Twin turbos, FMIC, T5. Built Ford Tough Moderator

02-04-2002, 05:19 PM	#3
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,514	Vacuum is better for a street car, when cruising at part throttle the timing doesn't advance so you'll get better fuel economy and at part throttle acceleration the curve will advance faster from the change in vacuum, whereas a mechanical advance is controlled by the engine rpm. For a drag car that doesn't need fuel economy, driveability or part throttle response and spends most of it's time at full advance (3000+ RPM) then mechanical is the way to go. If you do go with vacuum advance, find someone who knows how to re-curve distributors, it's becoming a lost art but it makes a big difference. BTW I'm only 24 and since the mustang mags don't talk much about carb tuning (except for some full blown race motors) I've learned a lot from HOT ROD and from other books about tuning carbs. __________________ 393W: AFR 205's, hydraulic roller, TKO600.

02-06-2002, 01:30 AM	#4
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	I have never seen a distributor that had vacuum advance, and did not also have mechanical advance. If you are asking if you should just use mechanical advance as opposed to using both, it depends on what you want to use the engine for. If you are building an everyday driver, I would recommend using both. If you are building a weekend only racer, i'd just use mechanical. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

02-06-2002, 12:42 PM	#5
David Fulford Registered Member Join Date: Oct 2000 Location: Charlotte NC Posts: 193	Is there an exact science or science at all for changing the springs that are in the MSD distributors for altering the mechanical advance. I just stuck the distributor(MSD8582)in as it came. I have several other springs and what not. Would I really get any noticeable performance gains from messing with it a bit? __________________ 1969 fast back; yellow; weld wheels; 302 roller with GT-40 heads; 3:55 gears; 5spd T-5; MSD 6AL; E-303; flows; Hedman headers; Holley 600;Weiand Accelerator;1.6 rockers

02-06-2002, 02:53 PM	#6
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Yeah, there is a science to it, actually. The lighter springs allow the full advance to be acheived earlier, whereas the heavier springs put the full advance off until a much higher rpm. When you want the advance to reach full depends on everything else, like your gears, your other engine mods, etc. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

02-06-2002, 03:13 PM	#7
David Fulford Registered Member Join Date: Oct 2000 Location: Charlotte NC Posts: 193	Makes sense. Thanks! I guess I will play with it a bit and see what happens. Although knowing me I'll screw something up. Later. __________________ 1969 fast back; yellow; weld wheels; 302 roller with GT-40 heads; 3:55 gears; 5spd T-5; MSD 6AL; E-303; flows; Hedman headers; Holley 600;Weiand Accelerator;1.6 rockers

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