Adjust your vacuum advance

Reply Subscribe

Thread Tools

Search this Thread

Dec 6, 2002 | 08:55 PM

Mike W

Thread Starter

Post Fiend

Joined: Apr 2002

Posts: 7,157

Likes: 1

From: Central Kali

Adjust your vacuum advance

I have been testing several distributors lately and almost all have too much vacuum advance. I know Crane makes an adjustable vacuum canister but I found another way to do it.

The Durospark has either a pin or a hole on the opposite side of where the vacuum canister lever attaches to the magnetic pickup assembly. I took a piece of 1/16 steel that fits the curve of the distributor and is held down by the gound screw for the pickup coil. Approx 1 1/2 by 3/4 ".

A small 1/2 by 3/8 tab with a hole is welded to the above piece. A 6-32 screw goes through the tab to a pivot on the pickup assembly. I had the one with the pin so I made a piece to fit on the pin that the 6-32 screws into.

At the other end of the 6-32 screw are two nuts with a lock washer between them. As vacuum rotates the pickup asseembly. The nuts will move towards the tab. You can set the amount of advance by changing the gap between the tab and the first nut. The second nut is to lock down the adjustment.

I have been testing this on a distributor machine but you could do it on a truck. Approx 1/4" of pickup rotation gives 10 degrees advance.

Dec 6, 2002 | 10:00 PM

Franklin2

Moderator

Joined: Jan 2001

Posts: 56,984

Likes: 2,738

From: Virginia

Adjust your vacuum advance

I tried this too on my truck awhile back when I had a 302 with a little bit too much compression. I was using the open slot that exists in the vacuum advance arm. It's hard to remember but I think I drilled an extra hole inbetween the two mounting screws for the vacuum advance. I would then put different size cotter pins in the hole. The vacuum advance arm would pull back till the open slot in the arm hit the cotter pin. It worked pretty good till about six months later I found out the vacuum advance had gone bad. I couldn't prove my little experiment caused it, but I was too chicken to try it on the new vacuum advance unit. So I just retarded the static timing a little bit.

Dec 7, 2002 | 12:04 AM

Torque1st

Posting Legend

Joined: Sep 2001

Posts: 30,255

Likes: 37

Adjust your vacuum advance

It does my old heart good to see you gents experimenting on these old distributors :-) Finding a distributor machine is hard these days.

B4 all the parts became "generic" there were different vac advance units that had differing spring rates and actuation or "pull" distances for different applications. If you get cozy with your local parts counterman at NAPA or CarQuest you might get to check out some alternate vac units sitting on the shelf all covered in dust that will fit your distributor. Other units can be modified to fit so you get that perfect spring rate, start, and finish points.

Thanks for using FTE!

[font color=red]As a Moderator I do not "Subscribe" to most topics,
please send email/pm if you need a reply -Thanks![/font]
-

Dec 7, 2002 | 01:29 PM

Post Fiend

Joined: Feb 2000

Posts: 5,130

Likes: 8

From: Brea CA

Adjust your vacuum advance

Mike, a lot of these Ford vacuum units are adjustable. Have you tried sticking an allen wrench up the nipple? It will adjust the rate but not the limit like you're doing. Just screw in more delay and you'll never hit the limit. The older Ford units that disassemble are better, you can change the rate and limit with different springs and washers. Unfortunately they don't fit the Duraspark.

Franklin, I had a similar experience after playing around with my vacuum unit. Was tweaking with the adjustment and screwed it all the way to the stop just to see how much travel there was. When it hit the stop I could tell I was torqueing on the diaphragm. Backed it off a couple of turns and everything seemed to be fine. About a month later the diaphragm ruptured, think it had something to do with me torqueing on it, maybe they're a little bit on the fragile side?

Eric, you don't have a distributor machine? Man, how do you live?

Barry

Dec 7, 2002 | 02:54 PM

Torque1st

Posting Legend

Joined: Sep 2001

Posts: 30,255

Likes: 37

Adjust your vacuum advance

I is just poor folk with no double car garage and a shade tree. My best adjustment tool is a gas hatchet. Of course some of this could change when I rebuild my basement... Two car heated garage with high door, pit/hole thru the floor and a shop below the garage :-)

But I still won't have a distributor machine. I have looked for a used unit, and on eBay, but the go for way too much money to justify for occasional use. I do have enough electronic equipment (scope, tach, v-spd drives, vac pump) to rig one up for a single use tho :-)

Thanks for using FTE!

[font color=red]As a Moderator I do not "Subscribe" to most topics,
please send email/pm if you need a reply -Thanks![/font]
-

Dec 7, 2002 | 08:35 PM

Mike W

Thread Starter

Post Fiend

Joined: Apr 2002

Posts: 7,157

Likes: 1

From: Central Kali

Adjust your vacuum advance

I got my Sun for $100. It has the roll charts for different year specs. The latest year is 1957! It was made to work off a 6v battery except for the motor drive. I put in a 6v power supply. The Durospark works ok on 6v.

I have checked a couple of the vacuum units with an allen wrench and no go.