Tech info wanted; Lean Burn Dist

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Bill Dedman

Bill Dedman

bill dedman
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I am having a hard time getting information about the timing of the two pickups in the Lean Burn distributors osed by Mopar in the late '70s. One of those pickups was retarded with regard to the location of the other. I just need to know how much.

There is probably something like 4, 5 or 6 degrees of retard built into this distributor, but it's so old, nobody has any info on it. It was retarded for starting.

Does anybody have the factory specs for the magnetic pickup offset in these slant six distrinutors (crank degrees,)???

Thanks for any information!:cheers:
 
Have you thought about a factory service manual for a particular year?
 
I want to say Dave, member "KitCarlson" knows this
 
Man, I can't find that specific information either.
Although I did find almost the same question when you asked it in 2012 when Kit recommended a method to find out but you didn't have a distributor yet to test with.

If you have one now you could do what I did for limiting max timing and print out a small degree wheel to attach to the rotor tower, an hei or Pertronics ECU and a coil and battery.
Fire a timing light on the degree wheel with one pickup and then the other and the difference between fires on the wheel will tell you what you want to know.

Kit could find out real quick if he has a lean burn distributor.
 
Bill, the info you want is somewhere on dot org, but that site is giving me fits, right now.
If you have the distributor, just put it in the car, connect either pickup, start engine. Check timing with a light, shut off engine, swap pickup connectors, restart, and check the timing again. That will tell you the amount of offset, and which pickup, is advanced, and which is retarded.
 
Charrlie_S said:
Bill, the info you want is somewhere on dot org, but that site is giving me fits, right now.
If you have the distributor, just put it in the car, connect either pickup, start engine. Check timing with a light, shut off engine, swap pickup connectors, restart, and check the timing again. That will tell you the amount of offset, and which pickup, is advanced, and which is retarded.
Click to expand...

Charrlie,

I guess that is what I am going to have to do, but, you have to understand that I am really
L-A-Z-Y!!!!!:pale:

I was just ryring to avoid the physical effort... When you get my age, you'll understand...:cheers:
 
What do you mean by WHEN? We're close, I'm 73. If you can wait till next week, I could probably do it for you. I think I have a dual pickup dist. My wife just got out of the hospital, so I have a little more time. I have to fix what I think is a vacuum leak on the engine first. I replaced the 2 bbl manifold with a 4 bbl, and it is running very lean at idle.
 
Charrlie_S said:
What do you mean by WHEN? We're close, I'm 73. .
Click to expand...

I'm 76... That's three whole years!!!! Over a thousand days!

It's a long @%$#^&*^$@!!! time! If you don't think three years is a long time, try holding your breath for three years... :violent1:

Thank you for the nice offer to test the retard amount for me. I can wait... Been waiting for 6 1/2 years;another week or two won't make much difference...:coffee2:
 
I think this info is in the mopar action tech archives (Rick Ehrenberg sells them on cd now, but I don't have access to mine at the moment).

That may be an avenue to check. I thought for the life of me that the pickups were independently adjustable, but I don't know why it's a struggle to find out. AutoZone stocks both distributor and the dual pickups.
 
jos51700 said:
I think this info is in the mopar action tech archives (Rick Ehrenberg sells them on cd now, but I don't have access to mine at the moment).

That may be an avenue to check. I thought for the life of me that the pickups were independently adjustable, but I don't know why it's a struggle to find out. AutoZone stocks both distributor and the dual pickups.
Click to expand...

The pickups in my lean-burn distributor and NOT adjustable, but it's a 6-cylinder distributor; the V-8 units may be different.

Thanks for the Mopar ACTION tip.:cheers:
 
Charrlie_S said:
The pickups are individually adjustable for air gap. They are not adjustable for offset
Click to expand...

Charrlie,Thanks for that information. According to the info sent by the next poster (Dave?) the air gap is different for the start and run pickups; .008" for the start (stronger signal at 008") and .012" for the run pickup. It also said that the connector was larger in size, for the start pickup. Handy information RE: the difference. That seems like a pretty wide window (difference) The article alluded to a retard of 4-10 degrees, so, I guess I''ll just have to bite the bullet and look at it with a timing light, for good information...

I'm getting there, but it's s-l-o-w....
 
madmax/6 said:
My lean burn dist has only 1 pickup.
Click to expand...

The lean burn system was the very first computer-controlled engine managment system Ma Mopar used, so they made constant changes to it in the enterest of improving it. So, some distributors only had only one pickup, while others had two. Some lean Burn distributors had mechanical advance mechanisms and a vacuum diaphragm, whike others had a locked-down plate and no diaphragm. Mine has two pickups a locked plate and no vacuum advance. It has the two ickups out-of-sync with each other, and they were used one-at-a-time; the "retarded" one was used for starting, and the other one was used for general running.

I want to use the more advanced pickup for stall-starting and off-the-line grunt, and switch over to the second pickup for the rest of the trip down the strip.

That sould give me 22-24 degrees of advance for stall-starting and switch back to 18 degrees, once underway (maybe 60-80 feet from the starting line.)

Anyway, it's just an experiment, but, that's the plan for now...
 
I learned something new.My dist is 1 pickup with no advance.I use a msd controller in the car,dail it back for starting and shutting car off.I dial it to 28 for my runs na and 26 with Nos.Sure makes timeing changes easy.
 
madmax/6 said:
I learned something new.My dist is 1 pickup with no advance.I use a msd controller in the car,dail it back for starting and shutting car off.I dial it to 28 for my runs na and 26 with Nos.Sure makes timeing changes easy.
Click to expand...

Mark.

Is your race car operational now?

Bill
 
Bill, I did the research today. here are my findings. From what I found I think a poor mans timing retard can be made using a lean burn distributor. This is the setup I used and I mounted the degree wheel on the shaft so pictures could be taken.
 

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Depending on which direction and which pickup you use first, you get either 30 degrees (dist degrees) or 15 degrees (dist degrees). Thats means you could lock your timing at 36 degrees using the second pickup selected then switch to the other pickup to start the car. the distributor I used is a small block lean burn from the late 70's.
 
You could, thru a relay, wire it up so the switching happens automatically when the starter is engaged. Correct me if I am wrong, Is 30 degrees dist timing = 15 degrees crank timing. If this is correct, you would have 36 total and 21 for easy starting.
 
Something you need to check is the rotor phasing. Remember, "when that thing" was being used, it was not a "direct" relationship like the non lean burn. The run trigger went through an electronic control, which delayed the spark in order to control the advance.........electronically.

I bet one of those pickups "is not" phased that is.
 
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