Electronic distributors and tuning them.

[1 Wild R/T]

The shard of steel on the magnetic pickup.

My shop is full of steel shards... But only one set of steel feeler gauges tucked away in my tool box...

 

[Kern Dog]

I bought these brass ones in 2001 when I got the MP ignition kit.

 

[Jonas Nordstrom]

Kern, does the distance differ much when checking with the feeler gauges?

On my newly produced Mopar perf dist the distance varied a lot.
I have not checked my old original one yet...

 

[Kern Dog]

If you're asking if I noticed a variance between the 8 points of the reluctor, I have checked and haven't been able to determine that for certain. The spec in the instructions is .008 which is amazingly thin. It seems to me that I could have a few points at .012 and I'm not savvy enough to know it.
Gauges that thin are hard for me to measure with confidence. Should there just be a slight drag when pulling them through the gap? My experience with feeler gauges for lashing rocker arms/valves has been with .014 and .016 sizes and with those, I can feel more. With those, I am confident.
My Mopar Performance distributor used to sometimes develop a spread in the air gap without me touching anything. One time, I was at a local drag strip and I expected a mid 12 second ET. My 60 foot wasn't great, something in the 1.95 range due to wheelspin but just past that, it started misfiring and sputtering to an embarrassing 14.XX ET. I had no tools to investigate. It ran smooth and idled great but at WOT, it misfired. At home, I found the air gap had spread to .020. It just didn't fire under heavy cylinder pressure but ran fine at light throttle. I tightened the screw a bit more than I used to prior and it has held for many years.

Part of the reason that I want to make a change is the design of the MP unit itself. It uses small advance weights and really light springs. I can run it to 3000 rpms and aim the timing light at the balancer and see the timing mark bounce around. I'm told that this is called "Spark Scatter". Feel free to set me straight if I recall that incorrectly. It moves around at idle as well. For years, Ehrenberg has criticized this distributor specifically because of that unstable timing issue. The tiny weights just have too little mass to operate smoothly.

I've considered using a stock rebuilt 72-78 year model 440 distributor but my local NAPA stores had trouble getting them.
When I saw a member here list a new one for sale, (That he bought and never used) I figured I'd give it a chance. Looking back, I bought this one in June of last year:

 

[kiwigtx]

Your eyes are better than mine. I had to get the reading glasses to see that.
It is probably a strand from the rivet I filed down. Maybe I'll give this a quickie blast of compressed air before using it.
Thank you.

You must get all steel fragments away otherwise you can get false timing and erratic readings.

Just trying to be helpful Greg.

 

[HALIFAXHOPS]

Never did use a 6 pickup but never thought it would be different.....just thought the reluctor would be the determining factor.

The six reluctor has just one grove in it for a roll pin and obv. six points. Yes the pickups are defiantly phased. One of the reasons for the "phasing" reluctors being made really. Have a 6 PU in a 8 la it is off, in a RB it is off, etct. If it is properly matched, you will never have any phasing issues. Just one of those things people came up with. Thats why the roll pin holes are set. If actual phasing was off it would be a random amount between parts.

 

[Cranky]

I do my best to keep my stuff tucked away. I keep the weather sensitive stuff indoors but other stuff sits outside. Body panels, axles, springs and wheels are outside of the car so they sit outside. Engine parts, interior, electronics and gaskets have to be protected.
File cabinets are excellent for storing small parts rather than stuffing them in boxes and stacking them.

The stuff that sits outside of the car is usually underneath it at least and most of the time being used. I've worked on enough rear ends to know what they look like inside if they've been out of the car and sitting on the ground. Stuff around here will sweat inside if left out in the elements when the weather is cool and dry and then a warm front comes in from the south with high humidity.

I'm fortunate to have a wife that is so easygoing about my interests, it would piss off the other wives.
She never hassles me about the money I spend, the shows I attend or the way I sometimes look. I try to balance out my hobbies with giving her full attention when she needs it. I am blessed.

My girlfriend now is like that. My X used to bitch about the work clothes I wore (mostly around the house though) and well, she was also always 'needy'....

I bought these brass ones in 2001 when I got the MP ignition kit.

I got mine when I bought a 72 340 Challenger in early 74.

 

[Jonas Nordstrom]

I was curious so I checked the gaps on the old original one I just got.
Yep, the gaps are very constant and only one feeler gauge blade did fit (in this case 010).
A big difference from my newly made dist.
Old stuff wins again.

 

[GTXDAN]

Watching the thread there is one thing I see you didn't show. There has to be a washer on the shaft above the collar that holds the shaft in, to keep the endplay to a minimum. If there is to much endplay that is why the T bar is hitting the rivet on the plate. If the endplay is correct they will never contact. The alignment issue with the reluctor will effect the way it runs because the phasing will be off with the rotor. That's why there are 2 slots in the reluctor, one for big block and one for small block. This changes the phasing.
I have been experimenting with a couple of RB electronic distributors and the HEI module conversion. They seem to work pretty good. I have mocked one up with a coil and a set of plugs and wires and it will fire even turning it by hand. I use a coil with low primary resistance so I don't need the ballast resistor. Everything runs on 12v which makes it simple. I am using this coil from Summitt, only $28 and 60,000v output

 

[GTXDAN]

From going back and looking at your pictures again it looks like there is a washer on the shaft. I have one distributor that has 2 washers on it. Even with a washer and to much endplay the t bar will contact the rivet. You might need to add another washer. Another thing is that collar the pin goes through that holds the shaft in, is sometimes not drilled in the center. If you take it off mark which way is up so going back it is correct. You can try turning it over to see if this will help the endplay. Sometimes the hole is drilled offset through the shaft and the collar will only go on one way. Stick a pin punch or drill bit through it to make sure it is aligned before you drive the pin back in. Don't ask me how I know.

 

[GTXDAN]

Here is my home made distributor run machine with the HEI converted dist mounted on it. I just clamp it in a vise to use it. 2 wires going to a battery and she fires away. You can see the HEI module mounted underneath. This works really well and you can hardly see it on the car. I put a connector in the wiring to the distributor so if you have to remove it you can just unplug it.

Next thing I am working on is adding a degree wheel to the shaft so when it is running I can see what the advance is doing. With a timing light with a tach built in you can see the speed when the advance starts coming in and when it stops.
Here's what it looks like inside. In the top of the distributor you see the pin that locates the plate inside of it. This is out of a 74 RB #3755518.

 

[kiwigtx]

I was curious so I checked the gaps on the old original one I just got.
Yep, the gaps are very constant and only one feeler gauge blade did fit (in this case 010).
A big difference from my newly made dist.
Old stuff wins again.

View attachment 1641347

A major variance in the reluctor feeler gauge measurements might suggest a worn bearing on the shaft.

 

[Kern Dog]

The notch is there in post number7, third picture from the bottom.

I missed it when I had the reluctor wheel off. With it in place, I really can’t see it.

I do like how Halifax Hops mentioned that the LA series has the roll pin in line with a terminal and the B/RB is offset.

 

[Jonas Nordstrom]

A major variance in the reluctor feeler gauge measurements might suggest a worn bearing on the shaft.

True. But in this case it was a brand new Dist that varied, while the old used one was spot on.

 

[Kern Dog]

I started this topic expecting to cover my experience with modifying the new distributor with the FBO advance limiter plates....

They haven't arrived yet.

The kit I bought included the distributor, ECM, ballast resistor and wiring. The instructions stated that the distributors already have a narrower advance curve and different springs than stock but I wanted to have this FBO plate to get it all right where I want it.

 

[HALIFAXHOPS]

True. But in this case it was a brand new Dist that varied, while the old used one was spot on.

Only way that can happen is the upper dist shaft is bent. One reason to check the gap on all the points. Been doing these for a long time seen alot.

 

[Charlie71rt]

I read that sometimes people have problems running vacuum advance with timing like we use 12-16 base 34-36 mech advance 48-50 with vacuum because the rotor to cap terminal is out of phase. The factory base of TDC the phase problem would not show up. I bought one of RE reluctors with multiple slots it came with good instructions except it doesn’t say when you use a timing light through a hole in the cap where and when the rotor should be in relation to the cap terminal, at base, cruise, mechanical all in and and total with vacuum, see post # 48 Bee1971. Can anyone expand on this.

 

[Bee1971]

Simple - Disconnect vacuum advance hose - Check it with the timing light through the hole at different RPMs thru the mechanical advance - It should bee damn close dead on and same thru all RPMs under mechanical advance with the #1 cylinder

Then hook up your vacuum advance hose to full manifold vacuum and do the same - Remember Big Block Distributors have Counter Clockwise direction

As long as it’s near or close to the vicinity of #1 - The problem occurs when or if the rotor would drift or say approach halfway between #1 and #2 cylinder under vacuum advance

Click on this link for a better explanation

rotorphasing

 

[Randy Wilson]

The 8 LA distributors I showed were all OEM as far as I knew. I pulled them from wrecking yards and parts cars I bought. They all seemed to have only one roll pin in them.
The two RE distributors I posted have two roll pins each, filling both grooves. The reluctor does slip up and down slightly on the one I had apart today.
I respect Ehrenberg and enjoyed reading his tech but I've also seen him stubbornly stick to some things that have been disproven. One of his claims was that one shouldn't use the later FMJR disc brake knuckle/spindle for fear of it over angling the upper ball joints leaking to failures. These have been used for years with zero reported failures yet he stands by his warning.
He is a strong proponent of using vacuum advance for street cars. He dislikes the coil over front suspensions for street cars. I don't know enough about ignition systems to dispute anything he says. I've seen the stock points and electronic systems run a long time in my cars and others so I'd need to see some accounts of problems others have had to get me to consider other systems.
For now, I'm going to try the FBO advance limiter plates like these:

View attachment 1640683

I agree with his ideas on vacuum advance, vacuum advance in its current form came about to enhance fuel economy and ring wash. It is not supposed to be part of the mechanical advance mechanism of a distributor. It’s like the overdrive gear in our modern automatic transmissions. It naturally find its way into that gear but the minute you nail down the throttle it disappears like was never there.

 

[Randy Wilson]

The 8 LA distributors I showed were all OEM as far as I knew. I pulled them from wrecking yards and parts cars I bought. They all seemed to have only one roll pin in them.
The two RE distributors I posted have two roll pins each, filling both grooves. The reluctor does slip up and down slightly on the one I had apart today.
I respect Ehrenberg and enjoyed reading his tech but I've also seen him stubbornly stick to some things that have been disproven. One of his claims was that one shouldn't use the later FMJR disc brake knuckle/spindle for fear of it over angling the upper ball joints leaking to failures. These have been used for years with zero reported failures yet he stands by his warning.
He is a strong proponent of using vacuum advance for street cars. He dislikes the coil over front suspensions for street cars. I don't know enough about ignition systems to dispute anything he says. I've seen the stock points and electronic systems run a long time in my cars and others so I'd need to see some accounts of problems others have had to get me to consider other systems.
For now, I'm going to try the FBO advance limiter plates like these:

View attachment 1640683

I agree with his assessment on vac advance. Vacuum advance, in its current form, was designed to increase fuel economy and reduce ring wash. It is not supposed to be part of the distributors, mechanical advanced curve. Think of an overdrive gear in our modern automatic transmissions. In normal driving it finds its way into that gear. But when you mash down the throttle, overdrive disappears like it was never there.