Mopar Performance RB distributors...Modifying for LESS advance?

[Kern Dog]

I recently replaced the reluctor and pickup in my MP distributor. Looking inside it appears that it is similar to others I have seen from Mallory. I bought it in 2002 as part of an electronic conversion kit.
I wrote in another thread about how I am having detonation problems with a 493 in my Charger. I have been advised that tuningwhat I already have may provide some help.
last year I tried a new ignition box from Rev-N-Nator. It looks similar to the factory ECU with a few minor changes. Due to its design, the ignition timing has to be reduced to avoid detonation. I have my initial timing set to 17 and the advance is limited to around 30/31. By reducing the timing to the point of no knocking, I was out of the sweet spot for a decent idle. I pulled the box and installed a chrome one. NOW I'm thinking of using the REV ECU if I can figure out how to modify the distributor.
The MP distributor has 2 screws in a gold plate that are visible once the reluctor and pickup are removed. Is it fair to say that if the slots are filed oversize, it will allow more adjustment?
If I am wrong, can anyone offer advice on how to modify this distributor?

 

[Funship32]

I don't know if this will help or not, but perhaps it will. My understanding is that Ma Mopar stopped making their own distributors several years ago and sub-contracted to Mr. Gasket (think of Accel and Mallory) to make them. So that is probably why it looks like a Mallory distributor on the inside. Also my understanding also is that while the unit itself is better built than the OEM stuff, the advance rate on these units is crazy fast as it is more like a race advance than a street/strip advance. So you either have detonation OR you have to back off the timing to the point where performance and driveability suffer. Sound familar? In theory you should be able to get a tuning kit for a Mallory distributor and adjust the curve rate as needed. Mopar Action had a super nice writeup about fine tuning the distributor in their Feb 2013 addition. I'd highly recommend you pick up a back copy. Hope that helps!

 

[RJS]

I just went though this with my MP Distributor.
You need the no longer sold kit P/N P5153446
The internals are from Mallory on these distributors.
After ordering that P/N at Sumitt, Mega,and a few other places and having it cancelled due to no stock I found one at YearOne.
There is a Mallory kit that would work too but the MP kit is more complete.
Ron

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I just went though this with my MP Distributor.
You need the no longer sold kit P/N P5153446
The internals are from Mallory on these distributors.
After ordering that P/N at Sumitt, Mega,and a few other places and having it cancelled due to no stock I found one at YearOne.
There is a Mallory kit that would work too but the MP kit is more complete.
Ron

https://www.yearone.com/Product/1966-74-a-b-e-body/p5153446

 

[snakeoil24]

If i remember correctly their is a replacment reluctor that improves the scatter issue. Also reduces misfires a great deal.

 

[Kern Dog]

I'm taking the car to a show tomorrow, 90 miles away. Maybe I can dig into it sunday to get a better look.
When I had the distributor apart a few weeks ago, the screws that allow the adjstment looked to be at the far end of their travel. It was because of this that I hoped I could file the slots further, allowing more adjustment. I am considering using the Rev-n-nator ECU that I bought last year. That spark box requires less timing and if I back mine off anymore, idle quality suffers. I want to stay with a reasonably tolerable idle and NOT rattle like a golf ball in a coffee can.
I'll admit the curve rate is really fast. Watching it with the light, it starts advancing right off of fast idle. There may be some additional gains by tuning that rate down a little.

 

[RJS]

Did you read my post????
The distributor is extremely tunable.

 

[Kern Dog]

Did you read my post????
The distributor is extremely tunable.

Hey!
Yes I read it, and thank you. I appreciate the info.
I'm not against spending some money to get things right. I was just curious if the adjustment slots could be slotted longer to reduce the amount of advance. I would certainly need the kit that you mentioned when I go to tune the rate of advance. If the kit you mention has a plate with longer slots than my distributor has, then I apologize. I didn't mean to piss on your advice!

 

[Garys1969RR]

My thinking is to reduce the AMOUNT of advance in the distributor. To around 16 to 18 degrees of advance at the crankshaft. This allows you to use 18 to 20 degrees of initial advance, and the centrifugal advance moves it to around 36 or 38 total. My 451 likes alot of initial advance with the 509 MP cam. Yours may like that too. Have you tried increasing jet size 2 steps all around? That should help with your pinging problem.

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On a stock distributor you weld up the slots to reduce the amount of advance, or find some other way to limit the travel. I just used a heavy advance spring that I stretched a little, to keep the weights from closing down all the way. Works real good.

 

[Meep-Meep]

Band-aiding a high compression engine by lowering the advance is not the best way to go about the problem but I understand you gotta do what you gotta do. Gary is correct, that to reduce the total advance in the distributor, you want to shorten the slot so the weights don't fly out as far. And add a heavier spring to slow the rate.

 

[kiwigtx]

If it helps anyone out... about 6 years ago I had to lengthen the slots in my advance plate just to get a decent amount of mechanical advance. The slots have to be ground out carefully so as not to damage the travel of the pins. This was on a distributor sold new to me supposedly as a MP unit from a large retailer in USA.....I suspect after looking at it, that the country of manufacture has a red flag. I have since replaced that distributor with a new USA made unit, and it works fine.