So I'm digging into the 440 that I picked up last fall and finally got around to taking a look at the distributor. Just as I assumed, but hoped wasn't true - a bronze shaft was staring back at me when I pulled the rotor. These distributors were sold by Mopar Performance starting in 1999/2000 and were produced by Mallory/Accel. They are known to have a really bad advance curve and suffer from spark scatter. Ehrenberg has recommended several times in print that the only course of action is to just throw them away.

For the very few miles that I ran this engine I did feel that the curve was way off, as it would idle just fine but seemed to fall flat on its face once you got on the throttle. Is there any hope? I don't know much about this style of distributor or if it can be reasonably modified. I believe the MP spring kit is NS1, if it would even help, and I seem to recall a suggestion about adding a collar to the shaft to control the scatter. The vacuum can should be adjustable, assuming it has enough travel to slow down the advance.

I had a pre-Mallory unit in my last 440 and it worked like a charm. This car has a 1967 block and 915 heads, so I'm guessing CR is somewhere in the 9s. Cam doesn't seem much more than stock. If I can't tame this Mallory hunk of junk I'll be looking at a remanned OE unit.

Thanks

I put one in my current 440 when I built it back in 2005. I don't remember any problems but I did switch to a billet MSD at some point. The DC/Mallory was supposed to be the latest and greatest back then but I remember some bad press on them. I did buy the recurve kit and got the advance where I wanted it before swapping in the shiny new MSD.

I bought one around 2006. Installed the locking collar on the shaft and recurved it to be all in by 2500. Along with an MSD 6AL it’s been flawless for 15 years in 70 440 Cuda.

Can I ask what your rear gear ratio is? Also stall speed if you are running an auto. Thanks

The main advantage to them is their adjustability. You can narrow the advance curve easily. R/E is right about the spark scatter though. Look at a timing light at approx 3000 rpms and watch the timing jump around. You have to look at the range that it operates in and assume that the center of that is the average when setting total timing.

3.55 4 speed, 28 inch tire (275/60/15). And I run the vacuum advance at about 54 total. 34-36 on the mechanical.

I bought the Mallory because I was having a severe spark scatter problem with the distributor that was in the car at the time. The Mallory solved that. And the locking collars are a good idea on any distributor of that shaft design.

That’s about where I’d like to hit, I have 3.91s with a 3,000 stall converter and 255/60s. With the converter I might have to push closer to 3k, have read some posts saying that the Mallory units keep advancing up to 4K and that the spring kits are counterintuitive. I will have to play around a bit.

I never had the spark scatter problem with mine but the default advance curve is very extreme. I bought the mallory kit with the springs and keys to change it but never did.

I have the scatter spark problem ( +/- 2 degrees ) BUT, I think at certain point my stock dist also got the scatter spark deal.

wondering why???

the actual Firecore units are based on same Mallory setup

Nacho, my understanding is that vertical movement of the shaft is one cause of the spark scatter. The other is an issue with the weights being too light resulting in not enough spring tension to keep everything stable through the advance curve.

Posting for reference:

https://static.summitracing.com/global/images/instructions/sum-850535-1.pdf

Based on the Summit link, I'm thinking two blue springs? Advance starting from just off-idle and all in by 2,800 rpm? Again this is for a street car. My trans converter rating of 3k seems to be pretty accurate - do I want/need advance beyond 3k to work with the converter?

I have an NOS MP spring kit somewhere in a box in the basement, but I'm pretty sure this is pretty much the same thing
and if you don't like it, they won't complain if you send it back:

https://www.summitracing.com/parts/SUM-850535-1

edit, ok I see you found that...good deal.

I think the only advantage to the MP kit was a few more keys and additional springs, which they didn't give you a rate for. You don't even really need the keys, drill bits will work in a pinch:

14° = .130” or 3.3mm or #30 drill

16° = .149” or #25 drill

18° = .167” or #19 drill

20° = .184” or #13 drill

22° = .202” or #7 drill

24° = .225” or 5.7mm or #1 drill

26° = .240” or 6.1mm or B drill

28° = .260” or 6.6 mm or G drill

Same keys, but couple more of springs... colored green as far I recall. I have the MP kit and the MP branded instructions got a decal over the instructions sheet adding these on the spring list. Can't recall if the curve graphic for these is an added sheet. I have not seen my MP kit in around 8 years.

I have read about the scattering problem due the axial play of the dist shaft. Tried to save the axial play with a leather piece inserted into the driveshaft slot to add some preload. The leather absorbs oil and don't get dried like the rubber garden hose which was another of the solutions posted around the web. Aside the shaft collar of course. Didn't change the scattering.

I thought once the scattering could come from the slott being larger in thickness than the dist shaft flat end which the leather piece inserted into the slot will also help on get it somehow fixed without any angle play

My guess is that some scatter is due to the design and is unavoidable. I just don't want mine to be measurably worse - it's not like I'm going to Watkins Glen this weekend.

Anybody have input on advance curve vs converter?