welding distributor?

[tdaver]

Hi folks,

I am planning to weld the slot on my Mopar distributor to limit total advance. I have figured out how much I need to shorten the slot but I don't know if I should weld the slots near the center or near the end. Anyone?

[dave571]

Near the outside end.

[TrashedCharger]

For a brief moment, I thought that the camshaft gear indexing slot was what was being talked about. I thought that maybe somehow it limited slop between the distributor and the drive gear. Silly me... Although now, in a nonsequator way, I do wonder how much rotating play can be found between the gear and the distributor? I would assume that it should be nothing, but I wonder if having a tighter fit would eliminate any?

And yes, for the curve weight slots, the outside of the slots can be welded and filed to tune the amount that the avdance weights travel outward from cintrifigual force with increasing speed. You want to be sure to file the welds after measuring how much material you want left and blueprint your entire distributor (and clocking of the cap) if you do this.

Thinking about the tunability of the distributor makes me wonder...

I understand that using a lighter weight return spring allows the weight to travel to maximum advance sooner, but I'm wondering if a series of springs could be used to further control it?

Say, instead of using a weld to block the weight from moving outward, you use a spring that resists compression, to allow for a little more advance than where the end of the spring would allow, when squished.

This would allow for the lightweight spring to get your advance in sooner, but not total advance, just enough (wherever you wanted it) quicker and then when the weight came into contact with the second spring, it would slow the rate back down. This could be useful for someone trying to dial in the power/ torque bands of their camshaft, torque converter, etc on the same ramp of increase on a scale (think of a dyno scale).

I know that when you tune an engine, you should set all of your components to peak in HP at the same range of RPM as well as Torque... Meaning you don't want an intake that allows peak power up at 7,000 RPM on the same engine that has a camshaft that peaks at 4,800 and a torque converter that stalls at a lower RPM than can be used in a powerband.

If you could tune the curve of a spring rate in the distributor, by controlling when that weight hit the additional stiffer push spring, holding the weight back, you could get a powerband match for advance and have the climb in advance after hitting the additional springs at a slower rate to closer match the rest of your output peaks.

Think about this- The weight begins to travel out, overpowering the light spring and hits advance exactly where you want it at a given RPM. You want more advance at higher rpm, so you don't want to deny the engine that, but you don't want the distributor to give it full advance, so rather than totally cutting it off with a shorter slot, you put a spring there, so the spring can squish and the weight can go out a bit further, but not at the same rate that the lighter spring allows.

I know you could use a heavier return spring to get the weight in and less advance at whatever RPM you are trying to dial the advance to, but it doesn't get there as quick as a light spring. This is essentially why you weld/ finish file your slots, to gain a quick advance rate without letting it get higher, but if instead of welding, you tapered how quickly the advance weights could reach the end of that slot with a second spring that held it back at a certain rate. This way, you get to X rpm at Y degrees of advance, but it doesn't end, like a weld does. This would eliminate detonation at higher RPM, but slow the end of the curve down, instead of slamming it to a dead stop.

Think of it like using a rev limiter on an engine instead of a kill switch at max rpm, only instead of controlling and governing your engine's rpm's rather than killing it, you would be doing this for your advance.

I may have to rig up a distributor with a few different rates of secondary push springs to block the weight and see how it bench tests.

[dave571]

You still need to limit the total mechanical advance, to prevent damage and detonation.

Adjust the slot length as required, then work the springs to do what you just sugested.

IE, on my 330 I run 35 total timing. 24 initial, so the slots are shortened so allow 11 degrees advance.

The springs say when it comes in.

I see on a lot of rebuilt distributors there is a heavy second spring, and it acts much like you described. It limits the total advance somewhat. In reality there is no benefit to this type of setup.
Underheavy throttle, you don't want more than 34 to 36 on most mopars regardless of how high you rev it (hence most all out drag cars use a lockdown dist) and the vac advance will give you more at light cruise if that is what you are after for economy

[TrashedCharger]

All very true. I suppose I wasn't thinking about vacuum advance, which would do that at cruising. I agree that you want to limit your total advance to eliminate detonation, no matter at what rate it gets there. I'm just wondering if this would allow me to tune the actual curve of rate that it gets there. The weight of the spring controls the rate, but with it, comes a dictated curve that isn't controllable, within the same spring. I think this may allow to control the actual curve within the rate a bit more.

I have also seen some people having a hard second spring on one of the weights, with a lighter one on the other. You are right in that it doesn't do much for the distributor. The weights are only going to go out and fight the pull of the strongest spring resistance. It changes the entire curve of the advance.

I'm just wondering if I could somehow make use of a lighter spring's quicker gain in advance to whatever rpm I wanted, then taper it off towards the end of the curve, before reaching peak advance. I could also adjust the second spring rate. So, basically, it would go through two circuits of curve rates on the same curve. The first portion would be quick, while the second portion would be a bit slower. I think that this would further help in preventing detonation, while still allowing a fast rate of advance climb at the beginning, where you want it, which is what I'm going for.

All of this, of course, governed by the length of the slot for total advance, as you were saying. Both of the slots and weights would have two springs. One light spring that was pulling the weight back and another spring that the weight would come into contact with at a later rpm.

This would also allow your distributor to give more initial advance at lower RPM if desired, while still maintaining a controlled longer curve without the use of a vacuum advance. Making your distributor the source for initial timing and not so much the clocking of the distributor on the engine. This would also make it way easier on your engine at startup, if you tuned the weights to go out a little at idle and then hit the second set of springs, giving the startup circuit less advance for ease of starting (very beneficial on a high compression engine that also uses a ton of initial advance like your car), but jumping up to a par advance curve while running and making full use of the higher octane fuel's combustion cycle.

I think I'm going to experement with this, because I have acess to a Sun distributor machine and I could blueprint and dial it in and have my numbers to see if it would or could benifit without risking an engine.

[dgc333]

Trashedcharger,
The stock distributor curve and some of the springs provided in the MP spring kit for the MP distributors provide for a dual stage advance.

One light spring is used in conjunction with a stiffer spring that has an oblong hook on one end. As the rpm increase the lighter spring controls the rate until the space in the heavier spring whith the post on the advance weight. The rate then slows down.

Back to the orignal question. You want to weld up the slots to the outside. If you do it on the inside then you preload the springs more and the advance will not start to a higher rpm. You want the advance to start to come in 2-300 rpm above ideal to prevent erratic idle.

[BigBlockDude]

Originally Posted by TrashedCharger

If you could tune the curve of a spring rate in the distributor, by controlling when that weight hit the additional stiffer push spring, holding the weight back, you could get a powerband match for advance and have the climb in advance after hitting the additional springs at a slower rate to closer match the rest of your output peaks.

Have you looked at factory distributors?

[TrashedCharger]

I've blueprinted several of them on a Sun machine, so I should hope so. I was unaware that Mopar made a secondary spring with an ovaled retainer that engaged at the end of the curve. I'll have to look into those. That sounds like it would do the same thing that I am after. Thank you for answering my question constructively, dgc333.

[dave571]

Depending on how much time you spend, you can remove weigh fromt he weights as aditional fine tuning.

Yes it does work to have different springs on the different weights. The weights and springs work collectively for and against each other.

[aarracer]

Welding NOT required!

ALL the tuning you will ever need for a naturally aspirated, mopar engines advance curve, can be done with spring changes ONLY! All the other stuff is basically a waste of time. You can dial in your initial, total and rate of advance with JUST SPRING selection. If you TAKE the TIME to try, it works excellent!

Cheers

AARRACER

[dgc333]

Originally Posted by aarracer

Welding NOT required!

ALL the tuning you will ever need for a naturally aspirated, mopar engines advance curve, can be done with spring changes ONLY! All the other stuff is basically a waste of time. You can dial in your initial, total and rate of advance with JUST SPRING selection. If you TAKE the TIME to try, it works excellent!

Boy, I have never heard anything further from the truth than that statement!!!!!!

A bone stock engine you may be able to dial in the distributor with a spring change but that is certainly not true if the engine has been modified.

A general rule of thumb is the more duration the cam has the more initial timing is required for a clean idle and off idle throttle response. The more efficient the heads are the less total timing is required.

For Example: Take a stock distributor that has around 25 degrees or so of advance in the mechanism and has a factory 10 degrees BTDC initial requirement and you wind up right at the desired 35 degrees of total advance that is the rule of thumb for a sb open chamber head. Put in a cam with more duration and you initial timing requirement can easily go to 20 degrees BTDC, set the timing at that and you now have 45 degrees total way more to the point of possible damage to the engine. Sure you could put in springs that limits the timing to 35 total at the max rpm the engine will see. But, the rate at which the timing comes in will be way slower than what the typical 2500 rpm the engine wants for maximum performance.

The only way to get maximum performance is to dial in the initial, the total in the distributor and the rate at which it comes in. If this was not true then virtually every aftermarket distributor (including the Mopar Performance units) would not have invested in a way of adjusting amount of mechanical advance via stops or bushings as well as offering various rate springs.

[pishta]

Mallory did it easy with its dual point distributor with the cam key and hop out spring chart. Cam key changed the slot length and the spring selection let you map your advance rate from a linear (2 of the same springs) to a hop out (light + heavy) You just could not have a slow then fast rate by design. My Mopar 2 piece billet monster mechanical E-distributor has 4 index holes for total advance and has springs for advance rate, and that cool tan cap.....

[aarracer]

Cheers

wrong screw

not in my performance one though

[dave571]

You can adjust the length of slots on an mp distributor.

It has a lock plate, that you release with a torx screw. Then set to the length you want and tighten up again.

I don't see how you can limit total advance with a spring change, other than to use a spring that is so stiff it doesn't move at all. Which would work very similiarly to welding up the slots.

This is a silly debate realy. Even if it can be argued that the slots don't need to be welded, it can't be argued that doing so is in someway incorrect.

[dgc333]

Originally Posted by aarracer

First 333

dgc333 "NOT TRUE "

dgc333 "QUOTE"- "If this was not true then virtually every aftermarket distributor (including the Mopar Performance units) would not have invested in a way of adjusting amount of mechanical advance via stops or bushings as well as offering various rate springs.

"Well you got this part right EXCEPT the MOPAR Performance part, lol." And I would sooner run the mp units than "every other aftermarket
distributor!"

You must not be paying attention to what Mopar Performance sells. There distributors are built by Mallory and do have an adjustable mechanical advance. The picture below is of the MP Billet distributor I am using in my 360. The button head cap screw below the pick-up mounting plate at 3:00 allows you to slide a stop back and forth to set the amount of mechanical advance. The vacuum advance distributors have the same arrangement for adjustment. They have been this way since around 2000.

Originally Posted by aarracer

-this discussion is for a MOPAR DISTRIBUTOR- NOT EVERY AFTERMARKET distributor - keep on subject - don't try to change it and discredit true information with ill informed diatribe!

You sir are the ill informed, see picture above.

Originally Posted by aarracer

YOU have to understand the Mopar distributor DOES NOT have any adjustable bushings OR STOPS (ask Ma Mopar , you WILL get the correct facts). And SECONDLY YOU have to HAVE done the work to prove YOUR ill informed statements. I have discussed this in depth with MOPAR and have built performance distributors from stock units for many years and run them on distributor machines, dyno's, street, and many many tracks, oval and drag!

I agree with you on a factory distributor and that is why folks interested in dialing in their advance curve using a stock distributor weld the slots or use other means to limit the timing.

Originally Posted by aarracer

Apparently You HAVE NOT! The only way to get maximum performance is to dial in the maximum recommended total in the distributor and the rate at which it comes in (WITH SPRINGS). MP says total in by 2000 rpm for performance units, by 1200 rpm for race units and the initial is inconsequential and WILL settle were it may! It will NOT make a LINEAR comparison from total down to initial (due to rpm change/drop)! OOPS, I guess you were actually WRONG TWICE LOL!

Go read any text on dialing in a distributor, it's a three or four step process depending on whether you have a vacuum advance;
Step one is to find the initial timing the engine likes by adjusting for max vacuum.
Step two, Then look at the mechanical advance in the distributor added to the initial you just determined., if it's more or less than the typical recommendation for the engine then adjust accordingly (high a high performance cam it will almost always require limiting the advance). Further fine tuning is accomplished on a dyno or the race track.
Step three, select springs to have the timing all in in the mid 2000's. Again the exact number is going to require dyno/track time and for a street car so seat time to make sure you have no part throttle detonation. If you have an MP distributor and the tuning kit it's easy, just look at the charts and pick the springs for the curve you want.
Step four, is to set up the vacuum advance. This is going to be done by seat time. You want around 50 degrees total at light load cruising with no part throttle tip in detonation.

Then again if your goal is max performance at the drag strip and don't care about less than WOT performance just set the max. Many folks even lock out the distributor so there is no advance. But if you want all around great performing engine that has great off idle throttle response, mid range performance, WOT performance and gets the best possible economy then this is what you have to do.

Originally Posted by aarracer

And while cam and head changes may effect performance there is NO BEARING on advance mechanism operation other than the requirement to modify it for best performance in local conditions!

More duration a cam has the more over lap it has this over lap creates an exhaust diluted mixture at low rpm's ( the lope you feel/hear in a performance cam). This mixture does not burn as fast as one that is less diluted. To get maximum power you need to have all the mixture burning and maximum pressure in the cylinder around 20 degrees ATDC. To get this with a diluted mixture you need to start the combustion process earlier. This is the reason a bigger cam demands more initial timing and smaller ones less.

At the other end of the rpm range the cylinder and port shape impact how well the cylinder fills and how well it's mixed. High swirl type heads and closed chamber heads with quench all improve the mixing and allow for a faster burn. Just like at low rpm's slower burn requires more timing faster burn less timing. This is the reason BB open chamber heads like 36-38 degrees of timing, SB Open Chamber heads like 35-36 and closed chamber magnum heads like 32-33 degrees.

Originally Posted by aarracer

I just talked to the tech line to see if I was still getting it right after all these years and they STILL SAY THE SAME!!! YES!

good luck with YOUR theories, but you should NOT MISINFORM others, before at least reading what MP has to say on this!.

AARRACER

I have no idea what you asked the MP tech line or what they said but if they really under stood the theory behind a 4 stroke internal combustion engine and what different changes make they would have told you much the same as I did.

As far as mis-informing folks I will leave that to you.

[charger_dan]

Originally Posted by aarracer

. . . and the initial is inconsequential and WILL settle were it may!
AARRACER

this passage applies only to race motors, right?
why wouldn't MP address the setting of initial advance?
as we all know, initial is a major factor in operability
(whether in staging lanes, or on the street).
not trying to be a smart-ass; just curious.

[dave571]

If you don't care about your intial setup then yes, you don't need to weld anything. Set the total, and use the springs to decide where it comes in.

Not the best aproach, but it works. Commonly done.

BETTER to set initial higher, as it will improve drivability/throttle response and idle quality.

As seen with my own example of 24 intial and 35 total.
With the cam I have, it runs extremely poorly if the intial is around 16 or less.

Generally, more initial is always better, as long as it will start. Nice crisp idle and throttle response.

I have curved several with the torx screw/plate as seen in the pic below.
Very nice to work with, and much faster than welding

[TK]

Well, I find the stock 24+ degrees of advance isn't good for anything with any overlap to speak of, unless it has crazy compression.
I have also found, that the Mopar books, aren't always 100% either, because of certain liabilities, or something.......
Before I found this site, I drilled my slots out longer, and put little bolts in there to limit the advance.
The picture above looks way more appealing.

[dgc333]

If you use the Mopar Performance distributor there is a kit with springs and spacers. The spacers are marked in 2 degree increments. Decide what you want for advance in the distributor pick the spacer for that amount of advance, loosen the screws, put the spacer in, slide the stop up against the spacer, tighten the screws and you are done. For the curve you pick the chart that matches the curve you and select the colored springs indicated, install them and you are done. To me it's is well worth the dollars compared to welding slots.

If you are going to go the weld the slot route take an old rotor and glue a 39 cent drug store protractor to it with the zero point over the shaft center on the rotor. Tape a piece of wire to the body of the distributor as a pointer and you can check your progress with out reinstalling the distributor and checking it with a timing light. Just remember that timing is expressed in crank degrees and cam/distributor degrees will be half so if you want 20 degrees of timing you will need to measure 10 degrees on the protractor.

FWIW, back in the early 70's when in college I was the lab instructor for an ASE Engine Certification prep class. We had a Sun distributor machine in the lab. We all were playing with distributors back then too. Mig welders were scarce so brass brazing rod was used to reduce the slot length in the distibutor back then, easier to file than a weld.

[kick_the_reverb]

Sorry aarracer,
It looks like you have outdated info - as others pointed out - it has been a few years since MP changed "their" distributor. The ones that are being sold are made by Mallory and have easily adjustable mechnical advance.
And, btw, don't trust everything the MP techline tells you. It might have been good in the past...I'm not sure that's the case now.

Ran

P.S. - I was prepared to get my remanufactured distributor modified, but I lucked out on one with 20 degrees of advance, which fits me for now (16 initial, 36 total). There are a lot of those out there, and they might work for mild performance applications.

[63Fury]

Originally Posted by dgc333

If you are going to go the weld the slot route take an old rotor and glue a 39 cent drug store protractor to it with the zero point over the shaft center on the rotor. Tape a piece of wire to the body of the distributor as a pointer and you can check your progress with out reinstalling the distributor and checking it with a timing light. Just remember that timing is expressed in crank degrees and cam/distributor degrees will be half so if you want 20 degrees of timing you will need to measure 10 degrees on the protractor.

That is what I did. My stock distributor had 14 degrees of advance so thats 28 degrees on the crank. My cam has a crap load of duration so initial timimng needed to be around 18 BTDC and I'm running ported and polished 906 heads so my total needs to be all in around 35 degrees... so lets see 35-18=17 devide by 2 and that gives me 8.5 degrees of advance on the distributor. I welded up the outer edge of the slot and filed it untill I had the 8.5 (actually I went 9). When I first tried to start the engine it was at 8 BTDC and she would not start, I bumped it up to 12 & tried, it hit but would not run, she then finally fired and ran at 16. I let it warm up and I set total advance at 35 and the intial is at 17. It starts good and has no pinging at WOT....Works for me

[aarracer]

Cheers

wrong screw

Not adjustable on my stock single point, dual point, stock electronic, and Mopar Performance electronic though! eh

OK throw in that (I think)lovely FULLY ADJUSTABLE MOPAR PERFORMANCE RACE UNIT (it has more adjustment than an MSD piece) - not in a street distributor thread ? eh.
Are you going to weld it lol!
I'm quite aware who have followed this threads initiator's previous engine threads so why throw this stuff in? eh

[dgc333]

aarracer, you really should take some input for other folks that have had experience with these MP distributors. The one you have may be a unit that was manufactured prior to MP making the change over to the Mallory guts. If you purchased it recently I would send it back and get one with a more current manufacture date.

The picture below is from the instructions that come with the tuning kit. You can clearly see the button head screw is there to adjust the stops so you can adjust the amount of mechincal advance.

[dave571]

Originally Posted by aarracer

That's an indexing slot that has NOTHING to do with max or min timing!
It is used to index the plate and magnetic trigger to the reluctor ONLY!
And by the way I have a brand new performance distibutor and for YOUR information IT DOES NOT have the indexing slot!

It's been polite so far but this is absolute bunk.

The slot length is the mechanical advance amount, as seen in the pic. No if's and's or but's.

It has absolutely no bearing on indexing/phasing the reluctor the pickup.
On a vac advance dist the indexing is done by bending the vac advance arm. On a non vac unit, you need to fasten the upper pickup plate to the lower pickup plate where you need it to be, to index/phase it.

I curve distributors professionally
http://www.davesmopar.com/serv04.htm
http://www.4secondsflat.com/Mopar_Distributor_Tech.html

I have curved several of the mp units with the adjustable slot length, and limited the mechanical advance with the adjuster slot. That's what it's for.

Clearly your understanding of distributor operation is flawed.

[pishta]

This is all above my pay grade.....I had the key system at one time, I think it was an Accel.

[aarracer]

cheers

Sorry wrong screw

Will there be welding on that Mopar Race Distributor?

[TrashedCharger]

Flipping INT3RN3T!!111... Misunderstandings are so plentiful online over little things!

I would go with the longer slot and limiter screw. This way if you didn't like it, it would be easily adjusted, without the need to completely disassemble the distributor and break out the heat.

I think you could limit your total advance with any slightly heavier spring that had an ovaled mounting loop, long enough to let the weight get where you wanted it to or close and have the spring limit it there. This would help with slowing the curve down a bit. It just comes in at the end, like a dual rate spring only a little bit more on an extreme end.

[rumblefish360]

Has anyone worked with the MoPar spring package? The new package. It comes with a bunch of springs, not just 2.

I think this is for the stock distributors. I'm not sure.

[TrashedCharger]

It's probably set up like a strip kit, so you can pick your poison from the batch but how many springs are in the kit?

[rumblefish360]

P5153446, contains 6 springs
For distribs shipped after 9/20/04

(Hummm, better dig out my recipts on the last one I picked up.)