autolite/prestolite dual point distributor

[lewtot184]

a friend gave me an old autolite dual point distributor out of a '59 383 tall deck. i've been messing with the thing for a few weeks trying to refurbish it and get it running. all the bushings, shaft and essentials were very good but needed a very serious clean-up and new wiring. i'm ready to run it but i found something that might be a no go. i'm thinking the points might be 90 degrees out of phase compared to a single point. i looked at all the old engine manuals i have and they show the cap plug wire sequence the same for all big block distributors. i can always do the "bubba" move the wires around on the cap thing but would much prefer to use OEM orientation.

so, the questions are: is the plug wire orientation different on the dual point? were there some later changes in point orientation thru the years? does anybody have a picture of a mid to late '60s point orientation? this distributor had an uninsulated copper wire pop riveted to the bottom plate; what is it? (possible internal ground, and what does it connect too?)

i haven't messed with prestolites in decades but don't remember having any kind of plug wire orientation or any other issues. any help appreciated.

 

[MWbirdLOVER70]

Halifax on here has a wealth of knowledge on distributors and related on here. Maybe he’ll chime in

 

[R/T Boy 67]

You can put the number one wire on any terminal you want, by moving the drive gear. If the rotor to drive tang on the early distributor has the same orientation as the original distributor for your engine, then install the drive gear as per service manual.

 

[lewtot184]

as of now this is what i think is going to have to happen. first i need to connect the copper wire at the bottom plate to the upper plate for good grounding of the upper plate. secondly i think i'll change the orientation of the intermediate shaft to allow the distributor vacuum advance to move toward the rear of the engine rather than changing cap orientation. i've got several good intermediate shafts so i'll set one up to do this.

one of the problems i'm running into is the distributor has a 9 degree plate and used a short heavy limiter spring and a vacuum advance with a light spring and a lot of degrees in it. after looking thru some old specs this distributor used 7 degrees initial timing and with 7-9 degrees centrifugal (per specs) total timing was only 21-25 degrees. the vacuum advance with the light spring and 26 crankshaft degrees made up close to 50 degrees at high vacuum. down side is throttle the engine and vacuum drops and there's too little advance. anyhow, all that has to change in the opposite direction. i need 18-20 initial with the cam i have and limit some of that 26 degrees vacuum which i've already done. looking back at some of the old prestolite early to mid '60s distributors they really had total timing issues if one is using factory specs. i have a '65 service manual had from what i can read it looks like the old 383 and 426's only had 28 degrees of total timing at close to 5000rpm. no wonder they weren't balls of fire!

 

[RJRENTON]

a friend gave me an old autolite dual point distributor out of a '59 383 tall deck. i've been messing with the thing for a few weeks trying to refurbish it and get it running. all the bushings, shaft and essentials were very good but needed a very serious clean-up and new wiring. i'm ready to run it but i found something that might be a no go. i'm thinking the points might be 90 degrees out of phase compared to a single point. i looked at all the old engine manuals i have and they show the cap plug wire sequence the same for all big block distributors. i can always do the "bubba" move the wires around on the cap thing but would much prefer to use OEM orientation.

so, the questions are: is the plug wire orientation different on the dual point? were there some later changes in point orientation thru the years? does anybody have a picture of a mid to late '60s point orientation? this distributor had an uninsulated copper wire pop riveted to the bottom plate; what is it? (possible internal ground, and what does it connect too?)

i haven't messed with prestolites in decades but don't remember having any kind of plug wire orientation or any other issues. any help appreciated.

The distributor cap layout is different and NOT interchangeable with a std Mopar cap. The rotors are also significantly different and NOT interchangeable. The engine's firing order is the same....just put the wires in the correct CCW rotation order: 1-8-4-3-6-5-7-2 as b4. The small flexible wire provides a ground for the breaker plate as the Prestolite design uses a ball bearing to allow the breaker plate to rotate CONCENTRICTLY about the shaft centerline, in response to the vacuum advance and the current does not go thru the bearing assembly. A superb design......just my opinion of course.....
BOB RENTON

 

[4vnut]

On a dual point i have the bare copper ground wire connects to the primary breaker point connection terminal. Just replaced mine with a new one. Soldered it to the bottom plate rivet.

 

[lewtot184]

i've got a ground wire made and need to stick it on. i mocked everything up on a spare engine i have on the the stand. it looks like i need to back the intermediate gear up 2 teeth and the everything lines up. a major problem i had was the vacuum advance hitting the heater hoses before i could get the rotor lined up with #1 on the cap.

i did some research with old motor manuals and service manuals and came up with a common scenario with the old autolite /prestolites. prior to the smog era they all had low centrifugal advance degrees in them and the only one i could find with something more than 7-9 degrees was a '65 383 (9-11 degrees). looks like '68 and later could have had 35 or more degrees in the distributor allowing for everything to be located in what is a more conventional location. i need at least 18 degrees initial and would rather have 20 but the distributor can't be made to rotate far enough with what i have. anyhow, moving the intermediate shaft 2 teeth is about a 40 degree swing and everything looks very doable. back in the day i used the super stock distributors and there isn't any vacuum advance interference and i also used them in a '68 b-body with no heater hose issues.

 

[R413]

That bare wire is a ground for the breaker plate.

the old distributors have a different clocking of the blade that goes into the drive gear. It is one post off on the cap.

as said you can make any post #1 and then follow the firing order from there.

 

[lewtot184]

That bare wire is a ground for the breaker plate.

the old distributors have a different clocking of the blade that goes into the drive gear. It is one post off on the cap.

as said you can make any post #1 and then follow the firing order from there.

Yep. I kinda put this on the back burner. I put the distributor in a couple of weeks ago and couldn't get the engine to start. Anyhow I had the little ground wire in wrong so I'll be getting back to this next week.