Will Delco-Remy centrifugal advance springs work in a MP distributor?

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Also normal mopar springs work in it also but way easier to use the kit so your not taking it in and out constantly. You can see it is at full advance also right now. Also just FYI the vacuum advance will not adjust total vac advance but when the vacuum will activate it.
 
Thanks so much, guys. I had no idea it was a Mallory YH! I ordered the springs and stick kit from Summit. So how do the sticks work?
 
Will do, halifaxhops. I've read the Mallory YH instruction manual. If it is possible, I'd like to adjust the timing curve of my LA engine, that probably has too high a compression ratio and open-chamber "J" heads, to run decently on 91 octane.
 
Alrighty then! That Summit instruction sheet was very helpful, scatpackbee. I've got my Mopar distributor wrench ready, hillbilly timing tape on the damper, and am going to call halifaxhops today for his advice.
 
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Adjustable Vacuum Advance | For A Bodies Only Mopar Forum
 
It was great talking to you on the landline yesterday, Ray. The Mallory spring kit from Summit is supposed to arrive today. Also, I've got to go to the hardware store and buy a No. 20 Torx screwdriver. Those centrifugal advance bolts are larger than Torx 15 but smaller than a Torx 25, so I figure they must be a #20, which is a bit of an unusual size, in my experience.

My vacuum advance canister is marked "8.5", which means it gives a total of 17 degrees of advance at the crank, right?

OMG, I think that until now maybe I have been running a total advance of 28 degrees centrifugal (centrifugal advance bolts all the way to the left end of their slots), 17 degrees of vacuum and 10 initial, for a total of 55!!

But it didn't look like that much with a timing light on the damper; honest!

So do you agree or disagree with the following: say I want to limit total advance to 32 degrees. That means I need to lose 23 degrees of total advance somewhere, and the only place to get rid of it is the centrifugal advance slots, so I need to eliminate about 3/4 of my centrifugal advance.

Of course my mentor halifaxhops said to get rid of only about 1/3 of it, so I'm going to try that first and see how it works.
 
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Total advance without vacuum advance is around 34-36 (or whatever your favorite number is) for most of our Mopar engines. At light throttle, low load, the vacuum advance provides up to 15-20 degrees in addition. It is not unusual to cruise at 50-55 degrees total.
 
Bill Crowell said:
It was great talking to you on the landline yesterday, Ray. The Mallory spring kit from Summit is supposed to arrive today. Also, I've got to go to the hardware store and buy a No. 20 Torx screwdriver. Those centrifugal advance bolts are larger than Torx 15 but smaller than a Torx 25, so I figure they must be a #20, which is a bit of an unusual size, in my experience.

My vacuum advance canister is marked "8.5", which means it gives a total of 17 degrees of advance at the crank, right?

OMG, I think that until now maybe I have been running a total advance of 28 degrees centrifugal (centrifugal advance bolts all the way to the left end of their slots), 17 degrees of vacuum and 10 initial, for a total of 55!!

But it didn't look like that much with a timing light on the damper; honest!

So do you agree or disagree with the following: say I want to limit total advance to 32 degrees. That means I need to lose 23 degrees of total advance somewhere, and the only place to get rid of it is the centrifugal advance slots, so I need to eliminate about 3/4 of my centrifugal advance.

Of course my mentor halifaxhops said to get rid of only about 1/3 of it, so I'm going to try that first and see how it works.
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Start there bill and adjust the vac can to start pulling around 10 INHG.
 
I have the exact same MP Performance distributor and the factory mechanical advance setting was way too long at something like around 30 degrees. With the factory mechanical advance setting, factory advance springs and my initial set at 5 degrees BTDC, my engine pinged at the slightest throttle opening.

I reduced the mechanical advance to 19 degrees and set the initial timing at 16 for a total of 35 degrees mechanical, plus around 15 degrees from my vacuum advance for a total of 50-51 degrees advance at cruise.

That’s where I found my ‘69 340 ran pretty strong with no pinging.

I read an article by Rick Ehrenburg questioning Mallory’s reasoning on such a long mechanical advance.
 
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Status update and bump-up on this Mallory YH distributor thread.

I've got the centrifugal advance slots set at about halfway, with one black and one blue spring. The detonation is all gone now, running on common 91 octane gas with ethanol! I'm very happy about that.

But this engine has a fairly large cam and compression, so it seems to want a lot of advance. I got the best idle with about 30 degrees of static timing cranked in! (I backed it off to about 12 degrees for test purposes, though.)

The problem is that right now the power is very modest, and I've got to set the curb idle up so high in order to keep it running that it's not idling through the idle circuit, so the idle mixture screws don't do too much. So obviously I need to advance the static timing so I can back off on the curb idle, get the carb mixture screws working and then make some more test runs.

halifaxhops told me to adjust the advance slots, and I surely don't want to disrespect my mentor in any way, but what do the rest of you guys think? Should I try static timing first, or go ahead and give it more static and more centrifugal right away? Please let me know what you think.
 
Bill Crowell said:
Status update and bump-up on this Mallory YH distributor thread.

I've got the centrifugal advance slots set at about halfway, with one black and one blue spring. The detonation is all gone now, running on common 91 octane gas with ethanol! I'm very happy about that.

But this engine has a fairly large cam and compression, so it seems to want a lot of advance. I got the best idle with about 30 degrees of static timing cranked in! (I backed it off to about 12 degrees for test purposes, though.)

The problem is that right now the power is very modest, and I've got to set the curb idle up so high in order to keep it running that it's not idling through the idle circuit, so the idle mixture screws don't do too much. So obviously I need to advance the static timing so I can back off on the curb idle, get the carb mixture screws working and then make some more test runs.

halifaxhops told me to adjust the advance slots, and I surely don't want to disrespect my mentor in any way, but what do the rest of you guys think? Should I try static timing first, or go ahead and give it more static and more centrifugal right away? Please let me know what you think.
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Not sure what half the slot is in degrees but I think you have way too much mechanical advance. I have a Mallory YH on the test bench right now, and the springs never do what the papers say they should do, and the adjustment sticks are off too.

I don’t want to go back and see exactly what you are tuning on, but you should be at 18-20 degrees initial if you have a small block. That means you only need 10-11 degrees mechanical. That ain’t much. And I would use the stiffest springs you can find and see if you can keep the curve advancing to at least 3500.

The other option (which is near impossible unless you get some custom springs or make something work) is to open the mechanical advance all they way up, set the initial to 20 and get enough spring on it that it advances all the way to max RPM. Set the total at as close to peak torque as you can and send it. But you have to keep an eye on the plugs and make sure you don’t run into detonation. This is the correct way to do it, especially if you have an ignition system that retards with RPM, and most do.

For a big block the process is the same, but the total will as a rule be higher.

Any time you can get the curve to advance to max RPM you will make more power. The issue is getting that done.
 
yellow rose said:
The other option (which is near impossible unless you get some custom springs or make something work) is to open the mechanical advance all they way up, set the initial to 20 and get enough spring on it that it advances all the way to max RPM. Set the total at as close to peak torque as you can and send it. But you have to keep an eye on the plugs and make sure you don’t run into detonation. This is the correct way to do it, especially if you have an ignition system that retards with RPM, and most do.
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This is more or less what I did on my big-block with a lot of cam. One super-light spring, one heavy spring with loop. Cranks at about 16 degrees, but as soon as it fires, goes to 27 degrees (the super-light spring stretches until the other pin hits the loop on the heavy one). Advance is gradual on the heavy spring thereafter.

I measured 35@4000 rpm and don't want to stand close to the engine revving it any higher. The 11/22 distributor tower I got from Hops will keep it from going over 38 mechanical under any circumstances (which as YR says, will be less due to ignition retard with RPM anyway).

Plus vacuum advance for street use (manifold vac, it doesn't advance at idle with only 8" vacuum and my QFT 950 doesn't have a nipple anyway). I think it's a max 18 degree can, don't remember but it's adjustable.
 
I need a spring kit for mine also. Its the original electronic distributor out of a 1975 chrysler new yorker. Anyone know a part number and where to buy it?
Thanks!
 
You have to watch which MR.G. Kit they are like the MP springs goes full fast!
 
yellow rose said:
and the springs never do what the papers say they should do
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A big problem with the papers is that there is a big assumption made. In fact its a ridiculous assumtion.

The reality is that the spring force changes whenever the advance is adjusted.
When we reduce the advance available, it reduces the tension on the spring.
So the retaining force on the weight is less than it when more advance is allowed.

Graphs and more discussion this post
Distributor springs

That, and the lack of compensation for the exponential increase in centriple force are two of the disadvantages of the YH-YT advance design, especially with big cams.
 
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I think I was getting the detonation because the really wimpy springs that came with my distributor gave me maximum centrifugal advance too soon. I've been trying heavier springs, but so far I haven't got very much MoPower, so today I'm going to try 2 blue springs, with the centrifugal advance slots set at maximum, to see whether I get my MoPower or detonation.
 
Mattax said:
See the link above.
Or this one might be easier to understand

As far as what the timing should be, see this post.
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At this point, Mattax, I am definitely attending the school of "trial and error" engineering!

You know what they say about an infinite number of monkeys and an infinite number of typewriters: Eventually they make it to the drag strip.

If that school of engineering was good enough for old Henry Ford (it was), I guess it will have to be good enough for me. As a side benefit, I sure am getting good at removing the distributor, making changes, and re-installing it.
 
Two silver (light) springs and the full 28 degrees of centrifugal seems to be the hot ticket! Static timing of 13 degrees BTDC with the vacuum advance connected, and it would probably like more. No detonation and the MoPower is good, but the secondary air door on my Thermoquad isn't opening as early as I would like it to, and I am wondering if that is because I need more advance or because I need to adjust the carb.

BUT HEY! Isn't that over 40 degrees of total advance? I thought you were supposed to use a max of only about 34. Yet it seems to run well this way.
 
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Bill Crowell said:
Two silver (light) springs and the full 28 degrees of centrifugal seems to be the hot ticket! Static timing of 13 degrees BTDC with the vacuum advance connected, and it would probably like more. No detonation and the MoPower is good, but the secondary air door on my Thermoquad isn't opening as early as I would like it to, and I am wondering if that is because I need more advance or because I need to adjust the carb.
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Something I’ve found that I’ve never caught with a timing light is that when the springs get too light, the advance mechanism will do weird things. Like advance a bit...maybe 2 or 3 degrees and then retard 4 or 5 and then start to advance again.

I do not understand why this is, or even how it happens. Certainly advance weight shape and mass have something to do with it, but it’s certainly above my education level to sort it out and possibly correct it.

Interestingly enough, when I replace the light springs with something else I get an all most identical curve without the advance/retard/advance situation.

The next time it happens I’ll take a video of it. Someday, when I have time to actually screw around with it, and if I have spare weights for that particular advance mechanism I’ll make changes to the weights to see what happens.

Or, maybe I’ll find a book that explains it.
 
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