Another distributor question

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Backally

Backally

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Bear with me guys, I'm trying to figure out what distributor would work for me and don't know much about them. I got a 70 340, need a distributor that I can adjust the mechanical advance. Looking at various aftermarket models but I have seen two different Mopar units mentioned on this website, one has the slots you have to weld and grind, which I have now and am not comfy tackling. The other seems to have a screw/tab arrangement. Are these distributors interchangeable? If if I wanted the screw/tab one, are they on small blocks and what years do they come on? Napa or O'Reilly or someone carry them?
 

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You won't find the screw/tab style in any factory car or at Napa, etc. That's a MP ignition conversion distributor. You might be able to find one for sale that someone has removed.
 
By the way, maybe you know, that's a VERY long advance. "15" is distributor degrees, IE 30 "at the crank" So you could only run about 6* initial with that top hat.
 
you can also use the limiter plate from FBO systems(i have them and it works well w/ the oem style distributor)
 
I copied that picture from someone else's post, but mine has the same "15". So I really need to go a different direction.
Thanks all, appreciate the info
 
I forgot to mention that I run an Accel "look alike" dist, looks just like a stock Mopar, takes stock cap, rotor, etc, but has an adjustable advance.
 
sense your not comfortable welding the slots on yours, you could do what I do....I very carefully drill and tap, to install #6-32 allen head set screws about 3/8 of an inch long, in each end of the top hat, to act as a stop for the weights, and then it's adjustable.
 
fanofpetty said:
sense your not comfortable welding the slots on yours, you could do what I do....I very carefully drill and tap, to install #6-32 allen head set screws about 3/8 of an inch long, in each end of the top hat, to act as a stop for the weights, and then it's adjustable.
Click to expand...

Can you post a photo or two of how you did this? I was thinking of the same thing
 
I don't have any photo's ( It's already in my car) but it's simply a matter of just drilling and tapping a very small hole in each end of the top hat.
 
http://www.forabodiesonly.com/mopar/showthread.php?t=198096&page=2

attachment.php


Check that whole thread out
 
and there you go...."Crackedback" has graciously come up with a pic. for you. The only thing wrong with this pic. is the standard allen head bolt. If you use that, the head of the bolt will likely hit the pick-up mounting plate, and won't allow the dizzy to spin, so it's better to use an allen head set screw, and just make sure it does not stick out to far. I'v modified a few dizzys like this....
 
fanofpetty said:
and there you go...."Crackedback" has graciously come up with a pic. for you. The only thing wrong with this pic. is the standard allen head bolt. If you use that, the head of the bolt will likely hit the pick-up mounting plate, and won't allow the dizzy to spin, so it's better to use an allen head set screw, and just make sure it does not stick out to far. I'v modified a few dizzys like this....
Click to expand...

Hope you don't mind, trying to help out.

Yes, the allen head interfered from what was said in that thread.

The allen set screw is a great idea. :cheers:
 
no not at all crackedback...glad you provided a photo. I think it was a big help for everyone here. I never saw that thread before.... and I thought I was the only guy to do this....LOL!
 
Backally said:
Bear with me guys, I'm trying to figure out what distributor would work for me and don't know much about them. I got a 70 340, need a distributor that I can adjust the mechanical advance. Looking at various aftermarket models but I have seen two different Mopar units mentioned on this website, one has the slots you have to weld and grind, which I have now and am not comfy tackling. The other seems to have a screw/tab arrangement. Are these distributors interchangeable? If if I wanted the screw/tab one, are they on small blocks and what years do they come on? Napa or O'Reilly or someone carry them?
Click to expand...

The second picture shows the guts of the distributor I bought last summer from Mopar, distributor only. It is Mallory based and online you can get the Mallory advance kit, which has stops to set the mechanical advance. This unit also cured the problems I would have with original mopar distributors, where the vacuum advance plate would wobble ( discussed at FBO ignition).

Ken
 
I like the idea, it's a very good one. Much better than welding and filing. Did you use a self-locking set screw?

One thing I thought about was drilling a hole in the housing, so you could adjust advance without having to disassemble the distributor. Pop a plug in to seal it up.

You find any of those $500 bridgeports lately... :) They are so expensive out here.
 
ken5124 said:
The second picture shows the guts of the distributor I bought last summer from Mopar, distributor only. It is Mallory based and online you can get the Mallory advance kit, which has stops to set the mechanical advance. This unit also cured the problems I would have with original mopar distributors, where the vacuum advance plate would wobble ( discussed at FBO ignition).

Ken
Click to expand...

The mallory kit is nice, you can set mechanical advance using drill bits as spacers. The spacing to degree amount has been posted.

I'm still trying to source springs so I can do them myself for fewer $.

I dislike the MP vac advance plate. It's a PIA for sure.
 
While iv been doing this same thing,iv welded and cut my slots.i read somewhere in an article tha a slot of .350 long will give the reccomended advance of 32 dagrees with a 10 degree initial..can anyone verify slot length for the advance desired.Tey seem to be pretty short.Iv seen some pretty good milling machine deals in the bay area,found one for 450..its not a brigeport tho..its a Sharp..but i can live with that.once again thanks for the help...J
 

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though it is an expensive alternative. i like my MSD pro billet dizzy. I ordered up a few limiter bushing for $30. They allow me to to run 22* initial and 36* total. or 26* initial and 36* total. it sure woke my car up.
 
I found this chart "somewhere." These are dist. degrees, not crank degrees

Modifying advance slots
degrees / slot size
6.............. .340
7................355
8................375
9................390
10...............405
11.5 ...........420
12...............435
13...............445
14...............460
15...............475
16...............490
17...............505
18...............520
 
crackedback said:
I like the idea, it's a very good one. Much better than welding and filing. Did you use a self-locking set screw?

One thing I thought about was drilling a hole in the housing, so you could adjust advance without having to disassemble the distributor. Pop a plug in to seal it up.

You find any of those $500 bridgeports lately... :) They are so expensive out here.
Click to expand...
Crackedback,the screws that mount the pick-up plate, actually line up pretty well, and you can access the stops by removing one of these screws , or by removing the vacume advance canister. I
just used a dab of thread locker once I got the advance to where I needed it. I'll keep my eyes open for a bridgeport...sometimes they pop up cheap.
 
So ideally if im using a new 9.5 cannister double that and subtract from 36 divide that so ruffly .375 ought to do the trick..now can i set up a degree wheel and turn the dist by hand and it should tell me what im advancing in degrees!!!correct or not...j
 
Forget vacuum, it "adds on" last. An engine can use considerably more advance--some up to 50-55 and more in some cases, under light load and "cruise" at highway speed.

1--Find out what your engine likes for initial

2--Find out what it wants for full power WOT

3--Subtract the two---that is CRANK degrees of mechanical advance

4--Divide by 2 to get DIST degrees, and refer to the chart. That is the length of your slots.

This whole dist/ crank thing comes from all the books and shop manuals. Just about every "spec" book I've ever read specifies distributor degrees
 
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