Mopar Performance race distributor mechanical advance

Posted By: Snoddas

Mopar Performance race distributor mechanical advance - 10/21/13 10:10 PM

Hi,
I have installed a old MP race ditributor part 4120942, think its from the early seventies. It have tach drive.

It seems to be looked, its have no mechanical advance. I have a new MP billet race distributor on my other car and that one you could adjust the mechanical advance with changing the slots (bigger or smaller) and lock it with a screw.

Havent disassembled the old race distributor yet but do anyone know how to adjust the mechanical advance, is it the same as the new billet race distributors (mopar performance)? Just change the size of the slots. I think its a kit for the right size, advance curve kit...

Thanks folks,

Posted By: JohnRR

Re: Mopar Performance race distributor mechanical advance - 10/21/13 10:20 PM

I don't know how to lock it , maybe be as easy as tightening a screw that I believe is under the rotor , but those old mopar race units are not adjustable like the current MP electronics distributor ...

I'll refer to Rapid Robert on how to adjust the mechanical advance on the old units , involves welding and filing , I'm sure he has his procedure on a clipboard on his computer for a quickie copy and paste because it posts it up a few times per week ...

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/22/13 06:35 AM

The new MP billet race dist have the same advance curve system as the mallory unit. Same way to adjust the mechanical advance.

Okay, I will search here again to see if Rapid Robert have post some about change the advance in the old race distributors.

The engine is dynoed with another dist. The egine want initial 15 degrees and total of 33 degrees. With this old MP dist I could choose of 15 or 33

Was surprised it even started with 33 initial. Must be the street compression... The old dist dont advance the ignition... Want initial 15 and advanced to total 33

Please help, the mechanical tach and the old gear drive distributor really does it!!

Attached picture 7896164-bild2.JPG

Posted By: Cab_Burge

Re: Mopar Performance race distributor mechanical advance - 10/22/13 07:23 AM

Quote:

Hi,
I have installed a old MP race ditributor part 4120942, think its from the early seventies. It have tach drive.

It seems to be looked, its have no mechanical advance. I have a new MP billet race distributor on my other car and that one you could adjust the mechanical advance with changing the slots (bigger or smaller) and lock it with a screw.
Havent disassembled the old race distributor yet but do anyone know how to adjust the mechanical advance, is it the same as the new billet race distributors (mopar performance)? Just change the size of the slots. I think its a kit for the right size, advance curve kit...

Thanks folks,

If it is one of the early tach. drive mopar distributors, iron case, not aluminum, it may have had the advance weights welded to make the distributor have no advance so they could use it on a crank trigger ignition. I have two of those now, they do not have the top plate in them with the pickup or reluctor wheel on the top shaft , you can see where they are welded up

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/22/13 08:17 AM

Its the aluminum one, part no 4120942.

Posted By: Cab_Burge

Re: Mopar Performance race distributor mechanical advance - 10/22/13 07:11 PM

It may have the same thing done to it, if you hold the bottom distributor shaft and try to twist the rotor and it has no movement either way it is probally locked in (welded advance)to the bottom shaft

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/22/13 09:00 PM

I only have one spring for the mechanical advance, the other was missing. It wasent locked or welded. The Slots in the advance plate is modyfied and measure 0.470 inch. I think its about 18 degrees mechanical advance.

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/22/13 09:05 PM

Is it any spring kit for these distributors?

Attached picture 7896729-bilden.JPG

Posted By: Oyvind Mopar

Re: Mopar Performance race distributor mechanical advance - 10/22/13 09:48 PM

So, if it has a slot, and is not welded, why is it locked then? I really cannot see the problem?

Posted By: Cab_Burge

Re: Mopar Performance race distributor mechanical advance - 10/22/13 09:53 PM

Quote:

Is it any spring kit for these distributors?

I use the Mr Gasket spring kit for the early GM point type distributors, works great

I have not treid using just one spring, others on here swear that is the only way to go for a hot street and strip motor

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 10/23/13 12:24 AM

Here's some info. EDIT The mr gasket light spring kit is 925B iirc. The MP kit is P2932675. the crane kit (which is no longer available new) had a plain spring a yellow spring & an orange spring & they recommended to always keep the OE light spring & sub in something instead for the heavy spring with the long loop on one end.

Attached picture 7896906-advancecurves.jpg

Attached picture 7896906-advancecurves.jpg

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/23/13 11:08 AM

Thanks but what do point x and point y means and singel and double spring. I have one spring installed right now, that gave my full advance directly. Its that a singel spring set up or what do singel spring means...

I will look in my msd distributor (which the engine was dynoed with) which parameters I will look at but I think I need full mechanical advance 18 degrees and kick in fully at about 2500 rpm.
What springs do I need?

Also the slots measured 0.470" have seen a table here that stated 15 degrees x 2 for that slot size, correct?

I want 18 degrees advance, should I aim for 0.390" slot size (advance plate). In a mopar muscle magazine article I read 0.370" was 20 degrees in advance plate.

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 10/23/13 02:39 PM

Point X is when the advance starts and point Y is when the advance is maxed out. Single/double means (1) spring or (2) springs of the OE light springs that come (1) to a dist. Reportedly the slot length/adv amount chart ain't dead on so file em slightly less than the chart because if you go too far it means another trip to the welder & yes you will have to be in & out of there several times till you get it dead on. I would find the initial your eng wants with the "vac gauge method" then shorten the slots to get 35 (SB) or 36-38(BB) total (both initial and total set with vac adv capped) then work with the springs then plug in/adj the vac adv. EDIT I see that race unit has no vac adv so that's 1 less subsystem to tune. After setting initial and total I'd mix/match springs till you get just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day no matter what RPM that makes the slots max out at. You want the curve to start (point x) several hundred RPM above your idle speed in drive

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/23/13 08:28 PM

Thanks! Did they come new with only one spring installed? shouldnt both weight have a spring (stock setup).

Attached picture 7897862-bild1.JPG

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 10/23/13 08:35 PM

Quote:

Thanks! Did they come new with only one spring installed? shouldnt both weight have a spring (stock setup).

I've never owned nor worked on one of the race units but I would think that they came with 2 springs but no worry, just set your initial correctly along with your idle speed & go from there.

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/23/13 08:56 PM

Yes, for the moment I only have one spring and installed the distributor on 15 initial pointing at # 1 terminal at distributor. What happened was that the total timing was still 15 degrees.

Turn the distributor to initial 33 which I want the total to be. The total was 33. It dont advance the mechanical or more correct, it go total mechanical direct.

I will buy a springs and install one spring to each weight (two springs). I hope it then not directly go the maximum mechanical total advance.

Hope you guys understand me, I'm swedish

Posted By: JohnRR

Re: Mopar Performance race distributor mechanical advance - 10/23/13 09:02 PM

Are you able to move the rotor back and forth by hand if you hold the shaft that keys into the oil pump drive ? If so then it's doing what it is supposed to do with 1 light spring and those 2 weights ... go right to max advance at idle.

That distributor is called a RACE distributor for a reason. If you want it to act like a street distributor then you'll need to put in springs similar to a street distributor.

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/23/13 09:18 PM

Yes I can, the mechanical advance work and I understand the total kicks in directly. I will put in one more spring and test and tune. I drive it to the races and want it to cruise in some way, even if it spit and roar.

Thanks fellows!

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 10/23/13 10:37 PM

Quote:

Hope you guys understand me, I'm swedish

Almost perfectly & your attitude is better than most. What double R said, get some heav(ier) springs in there so you can drive it then go to work on tuning it. Somewhere between 10-20 initial (depending on the cam etc) & 36 total & 2 springs would be a good start. Just me for a DD I'd find one with vac adv

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/24/13 06:15 AM

Will pick up a new spring kit tomorrow. Dont know what brand but as I was told they are for recurve the mopar distributors.

On dyno the engine worked out best with initial 15 and total 33 degrees. That it was I aim for...

Thanks again!

Posted By: 3ddart

Re: Mopar Performance race distributor mechanical advance - 10/24/13 02:18 PM

here is a list giving distributor slot lengths for different degrees of timing. i had to weld my slots up on my hemi with the race distributor as if i set the initial to where it would idle the total was 45ish and if i set total at 38 it would die at idle. welded them up and demeled and filed them to get 14 degrees initial and all was fine then. Dave

Attached picture 7898756-distributorslotlenghths.jpg

Attached picture 7898756-distributorslotlenghths.jpg

Posted By: 1969gtx

Re: Mopar Performance race distributor mechanical advance - 10/24/13 07:16 PM

If you only have one sping the advance will go max limit at a low rpm maybe cranking rpm. You need to add a sping then see if it has advance.

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/24/13 09:42 PM

Did you measure the final size of the Slots. Did it in some way ended up like the size/degree as the tabel? Do you know what spring you use. I assume you use Two springs. But was they light or heavy.
Yes 1969gtx, it advance directly with one spring especislly when the point where the spring is mountrd was bend towards the spring.

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 10/25/13 01:44 AM

Quote:

when the point where the spring is mountrd was bend towards the spring.

Could be someone used a non Mopar spring & likely bent that so the spring they used (probably a shorter one) would work

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/25/13 08:56 AM

Today I will pickup the spring kit and do some test and tune.
I checked my MSD pro billet ditributor and it had the big black bushing (18 degrees mechanical advance) and one heavy silver spring and one light silver spring (not fast or slow curve just in the middle).

This is what I will try to copy on the old MP tach drive distributor. Probably need to shortened the slots on the advance plate...

Thanks for all help guys!

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/26/13 12:27 PM

I got two springs for ford but they worked, maybe kind of light also but will do some more test and tune. Now it dont get all mechanical advance directly. Unfortunatly its advance about 30 degrees...

I will modify this part to get the correct mechanical advance. What is this parts name, advance plate?

And mine is marked AC.

Have seen marking on others here on internet as 11R and 15L but that assume is the degreesX2 of mechanical advance but what is the R and L, right and left? If, should R plates be used for smallblock (rotating direction clockwise) distributors and L ones for bigblocks (counter clockwise) dists.

Cheers!

Attached picture 7901164-plate.JPG

Posted By: Cab_Burge

Re: Mopar Performance race distributor mechanical advance - 10/26/13 06:21 PM

Your right on the factory markings on the numbers and letters, right is clockwise and left is the other way

The numbers are the amount of distributor degrees advance, not crankshaft degrees, so if it is marked 12 it ends up having 24 degrees advance at the crankshaft

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 10/29/13 08:49 AM

I tig-welded the slots a bit and machined them to about 0.390 inch. Now I am bang on target on the total (and initial) timing. Maybe do some more testing and tuning on when it kick in. Have maybe some Mopar OEM springs waiting.

By the way the tall-tale on the mechanical tachometers is a really kool feature!

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 10/29/13 02:44 PM

You're almost there

. I'd mix & match springs so the mech advance starts a couple of hundred RPM above your idle speed in drive which is what the eng will see stoplight to stoplight & then with just enough tension so you are just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day.

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 11/05/13 07:25 AM

A friend of mine borrow me this spare distributor parts.

The two weights (Part #1889284) I think is for small block distributors?

The green spring which have the big loop on one side must be the heavy OEM spring.

The first from left must be the light OEM spring?

The other two short coil springs looks like mr. gasket 925B or Mopar performance recurve kit??

The broken/bend spring I dont even know if its a spring for a distributor.

Thanks!

Attached picture 7912716-bild.JPG

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 11/05/13 02:46 PM

Quote:

The two weights (Part #1889284) I think is for small block distributors? pretty sure & I will check

The green spring which have the big loop on one side must be the heavy OEM spring. correct

The first from left must be the light OEM spring?
appears to be yes
The other two short coil springs looks like mr. gasket 925B or Mopar performance recurve kit?? looks like em

The broken/bend spring I dont even know if its a spring for a distributor. I agree

Thanks!

Posted By: Snoddas

Re: Mopar Performance race distributor mechanical advance - 11/07/13 07:55 AM

Haha Possible full score on the spring and weight test.

As I mention shortened the slots in the advance plate about 0,04" gave me 18 degrees mechanical advance.

Will now test and tune springs. I'm quite happy about the ford advance kit springs I have installed but will try two light mopar OEM springs. You couldent be too happy have ford part on a mopar...

Stay cool!

Posted By: RapidRobert

Re: Mopar Performance race distributor mechanical advance - 11/07/13 06:13 PM

Quote:

Will now test and tune springs. You couldent be too happy have ford part on a mopar.

(1) Mix & match the springs till you are just under the pinging point at WOT up thru the gears. (2) since the springs are small (& generic) & hidden we'll let you slide on the furd parts (this time)