I'm of the impression that the Chrysler electronic distributors have both vacuum AND mechanical advance. Is this correct?

In that case, are the stock weights acceptable for finding a good advance curve for a stock slant, so I could just adjust the vacuum advance? If yes, what increment should I go by when adjusting it (full turn, half turn, quarter turn)?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Some of them do, yes, and those are the ones you want to use in most cases. The ones without vacuum advance are for use with Lean Burn.
The flyweights themselves are fine; the centrifugal advance curve gets dialled in by changing the springs and the lengths of the flyweight slots in the governor plate.
Some of the vacuum advances are adjustable, yes, but the vacuum and centrifugal advances serve different functions, and there's usually little to be gained by just randomly tweaking it this way or that way. Much better to map-out the existing vacuum and centrifugal curves, spend some time thinking about what you want to achieve/change, and go about it systematically.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

And that's where I get lost completely. I wish there was a guide somewhere that I could go off of, but everything I've found still breaks it down to trial and error. Not such a bad deal if vacuum's all you're adjusting, but when it comes to taking apart the distributor and swapping out weights and springs, that makes it a great deal more involving.

Then again, the more involved I get with my engine, the better I'll know it...

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Remember, you can't adjust how much vacuum advance you get: That is a constant. You can adjust when it comes in by turning the screw inside the can where the hose connects. For example, a stock advance can may come on at 10 inches of vacuum giving you 8 degrees of advance. You can adjust the can to start pulling at 20 inches of vacuum, still giving you 8 degrees of advance. Take an afternoon and play around with the distributer. Heck, it took me days before I got mine where I wanted it (yes, I was good at R@Ring the distributer). DusterIdiot is good with distributer recurving...see if you can contact him and get some info on the best curve for an A body. Mine is set up for a heavy (3700lb) car and may not work best for you.

just an odd ball ? has anyone used the mopar timing curve adjustment kit part # p5153446 I see it is now listed in the new performance book. In the book it has this description "kit contains six different primary springs three different secondary springs and 2 degree key set, allowing you to adjust timing to your performance needs" can anyone tell me if this is worth it at $27.00 or just a waist of money

The only other alternative besides trial and error is tuning a programable timing computer on a steady-state dyno. That is also trial and error, but you don't have to disassemble anything to change the curve. Of course, this approach is pretty expensive compared to swapping springs on a test and tune night at the dragstrip.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

You can, actually. You can reduce it by twisting wire around the pull rod at its shoulder, or increase it by grinding the shoulder. Also, there are a bunch of different vacuum advance units available, each with its own total amount of advance and initial calibration.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeh,

I got so addicted to working with the Emsvitil style graphs from an old thread that I bought a Sun distributor machine, a group of good used distributors, and the selection of vacuum cans that were in a thread a while ago.

It saves a lot of work, I think, setting up six or eight distributors in a matrix of tests, plotting each using the Sun, installing one in the vehicle, running it and making notes from the vacuum , tach and adjustable timing light in the vehicle, then swapping in another distributor and repeating.

Yes, the Sun was several hundred dollars but it saves me time and lets you me up distributors outside of a vehicle. Plus it is darn cheap self instruction on spark and performance for me. It took the intellectual down to the practical. Kinda like Dyke's Instruction set on spark advance from 1904! You would be surprised how fast you can swap distributors in and out of a vehicle once you get a stack to work with and a tad of experience doing it!
rock
'64d100

Well, it's not really quite purely random trial and error, more like educated/thoughtful trial-and-change-and-retrial. But, no, there's no spec you can follow along the lines of "Use such-and-such a spring, lengthen the slot to such-and-such a length, and that's the best setting", because the optimal curve is going to differ from engine to engine and vehicle to vehicle. Don't know what your budget looks like, but you may want to buy another distributor to work with. I bought a couple of these and Doctor Dodge analysed them and found them to be set up with pretty good curves right out of the box. Also see this thread for discussion and pics.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

My distributor machine was the car..........

And you do get pretty good at R&Ring the distributor.

Here's the thread rock was talking about:

http://www.slantsix.org/forum/viewtopic.php?t=13264

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

roadrunner, the mopar 5153446 kit is for the new mallory/mopar distributors with adjustable mechanical advance.{i have one of the new distributors in a crate 380. the kit makes setting the advance curve easy.}the keys are used to set/measure mechanical advance distance in the slots, which are adjustable. you could use the advance springs, but thats about it for 27 bucks. most guys just remove the original stock heavy/thick distributor advance spring and put one of the mopar p2932675 quick advance springs in its place. with your original stock light/thin spring and a 2932675 spring it gets your mechanical advance all in between 2000 and 2200 rpm which is good for street driven cars. if both mopar light springs are installed the advance is all in by 1500 rpm which is too early for street cars. the p2932675 spring kit is about 5 bucks for 2 springs. ron

I was going to get the kit you recommend but mopar does not stock them and the stock they now have is back ordered and it does not look like they are going to be getting anymore in anytime soon I was thinking about using kit # p4007968 for just 2 springs but my cost is $37.50and it lists for $47.00 so I was thinking about the kit for the mallory and new dist. cuz my cost is only $22.00

Go to the wrecking yard and gut the springs out of a few distributors.
Or I can sell you a few 'points type' distributors... cheap.
DD

Now kids...dont try this at home....

After spending an afternoon with Doug recurving distributors in the pits in LV and reading Eds meticul;ous research on his car I dove into the slant pile and came up with a number of spring sets.

I tried a few and was pleasantly surprised to find the stock 65 Prestolite cast iron dist gave me the best result.....transplanted to a 75 EI setup. I am able to run 10 static advance ....start the curve up quickly and be all done by about 2500 rpm (my torque peak) .

I used DIs recipe for the vacuum advance.

The result was astonishing...the car woke right up and got nasty.

This took one afternoon and got me very close to optimum. Could it be better?....of course. But 1 afternoon for 90% result with scrounged parts sounds like a bargain to me.

The trick is to start a process of trying and learning.....get some materials to work with and learn by reading. Start with Eds post!

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Yeah....Im the one who destroyed this rare, vintage automobile.....