Primary Spring & Rate 48lbs
Secondary Spring 21lbs Rate 69lbs (primary + secondary)
Secondary engages after about 12 degrees advance

Test 5.1
10 degrees initial
some hints of pinging 2500-3000

Test 5.2
8.33 degrees initial
clean, no pinging

Test 5.3
11.66 degrees initial
more pinging, clears at about 3750

Ideal curve adjusted after this test.
2500-3000 range flattened down (curve more linear here)... the 10 deg initial curve should not have pinged as the hump at 2700 was meeting the previous ideal curve, thus the adjustment.
3500-3750 range upped. (also makes curve more linear).. the lack of ping at high rpm, when it looked like it should.

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

Changed primary to 56lbs

10 degrees initial,

Made a test run and ran out of gas...............


What I did learn from running out of gas.........

1. Having a bad sending unit sucks
2. My every 200 miles get gas rule doesn't work when doing a lot of testing(esp when the car isn't moving and your running the engine alot)
3. It's good to test close to home, coasted to 1/2 block from home and got the remains of my lawnmower gas. (about 1/3gal)
4. My electric fuel primer pump helps when you're mostly sucking air in the tank to get home.
5. The gauge actually works a little....... it reads 1/8 tank when absolutely empty, and 1/2 a needle width above 1/8 tank when there's gas in there.....

Didn't trust my ability to make it to the gas station, so I went in my truck to get some gas in my gas cans and then I went and filled the tank after dumping my gas cans into the tank. So I quit my testing for the day after that.

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

All in the name of science!

ed

thanks for the input. Already was fiddling with the idea of boosting the car after doing the EFI conversion. Wouldn't be happening during this year or next year first half.

will keep the board posted anyway.

Your guess is correct about my cam. Longer duration, stock lift for the "upgraded" marine division cam. Nasty lobe profile (I have to run it tight and I mean tight, practically zero lashed. works great above 1500-1800 rpm.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Good testing, having built distributors for a living most of my life...it is rare that someone takes the time as you have to discover the nuances of distributor curves.

One advantage I have, is I've owned various distributor machines almost my whole adult life...here is the one I use now...a 1944 Allen Synchrograph.



I've modified it to work with all types of electronic ignitions. Funny thing was that I was using an identical one for years but it was WELL used...one day, a neighbor stops by and noticed it, he wheels an almost brand new identical one over to my house that was in his basement when he bought the house 25 years ago. So he gave me a virtually brand new 1944 distributor machine!

Anyway...I always provide an Excel spreadsheet graph of the curve much like yours with all the distributors I build.

Things to keep in mind...

If you have a performance car with a stall convertor the curve is unimportant, because you will be at total timing by the convertor stall rpm.

If your springs are too light, some of your curve may already be in at idle (a huge problem with GM distributors and HEIs in particular)...So that if your distributor has 20 degrees crankshaft mechanical, but at idle the springs are so light that 5 degrees is already in...then it will only have 15 degrees usuable curve. More important, the timing can move around with changing idle speeds. Also, if the springs are too light, it is difficult for the springs to overcome friction to close the weights all the way so that setting the timing in the driveway does not always reflect whats going on in traffic at different oil temps.

Don't use grease in the distributor weight areas...only use light machine oil...the oils will evaporate out of the grease over time and friction will increase with the sludge the grease becomes...I see this all the time.

Cars with low gears can have much more aggressive curves because the load on the engine is much lighter compared to a tall geared car....in other words, a car with tall gears can benifit from a non linear curve that brings in a little timing quickly(say 10 degrees) for good low end and throttle response, and then hold off on some of the rest during mid range rpm, and bring in the total at higher rpm. (this is the typical Mopar extra long spring at work) I do this in GM distributors by grinding the weights and cam to change the leverage at different points in the curve.

This last concept is important because often a tall geared car will detonate(ping) in the midrange because of the high load on the engine. Most people just retard the timing and the pinging goes away but at the expense of good top end and great low end. I've used this concept to totally wake up otherwise lame performers. Most people just retard the timing to eliminate the ping...but then you lose the low end response and the proper total for good top end.

Last...vacuum advance...its purpose is only to increase timing at part throttle higher rpm cruise for fuel economy. I always set mine up so that it takes a fair amount of vacuum to initiate the canister. When cruising the freeway at steady state, the vacuum is very high and will pull in the timing. What you don't want, is for the timing to initiate on light loads like long hills or climbing thru the mountains...destroying your piston rings with light load or inaudable detonation. The gain in fuel economy from vacuum advance at light loads is negligable, and the risk is high.

An engine can still develop many inches of vacuum while climbing a hill...so as an example, lets say your climbing a hill at 2500 rpm and your total timing is all the way in at that rpm of say 32 degrees (and you don't normally have any pinging and are happy with your setup)...now its a hot day and your engine and underhood are 15 degrees warmer than normal...on this hill, you are developing 8"'s of vacuum, if your canister doesn't start pulling timing until 12 inches...then no problem. But what if your canister pulls 7 degrees at 8 inches...all of a sudden you have 39 degrees timing climbing this hill...not a problem with just you in the car in normal temps...but today you've got a trunk full of picknic stuff and four people in the car and it becomes a pinging nightmare as your block starts ringing(the pinging noise) and piston rings start bitching at you...

Typically, you want about 45 degrees going down the freeway for max economy...because the engine is lean(slow burning mixture) and the compression is artificially low(throotle blades limiting cylinder filling).

So to set up your curve you take the mechanical advance at your freeway cruise speed, and then set the vacuum advance to make up the difference to get around 45 degrees, and set the tension of the canister to not pull in the timing until a vacuum reading that is not much lower than your cruise vacuum...say 15"s if you cruise at 20"s.

I could go on for hours...but I haven't got hours...

Gearhead

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"

Lots of good info here.

Soon, the Megasquirt II unit will come out as an add-on to the existing Megasquirt board, which I have on two of my cars. This will allow full timing map programming. Having screwed around with several dists to get a good curve, I'm excited.

Lou

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Home of Slant6-powered fun machines since 1988

I have this problem now, 9R governor, standard springs, initial at 6* BTDC, 2.45 rear gear and 4 speed. The engine really loves about 10* - 12* BTDC but pings to much to drive that way. What would you suggest as a fix?

You can up the preload on the primary spring, but a stiffer primary spring should help..... that's what I've been finding out...

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

Well once I get started on something I'm rather stubborn....

Wish I had a distributor machine, it would make life easier on the distributor adjusting, but you still have to discover what advance curve the engine wants......

Now test series 6........

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

Primary Spring 56lbs
Secondary Spring same as Test5 21lbs (77lbs when it engages)

Test 6.1
10 degrees initial
no ping

Test 6.2
11 degrees initial
no ping

Test 6.3
12 degrees initial
hints of pinging 2500-3000


Ideal Curve raised slightly to match 11 degree test 2500-3300.





I'm going to try a 61lb primary to try to raise my initial timing to 12.5 degrees. Also looks like I can delay the engagement of the secondary spring a little to let the higher (3500+) part of the curve rise more steeply.

BTW, at 10degrees I had the vacuum hooked up for a freeway run, no pinging with vacuum at that point.

Onto test series 7...............

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

Primary 61 lbs
Secondary 21 lbs (82 total) engagement delayed to 22 degrees (10btdc)


Test 7.0
10 degrees initial
no test, looked at the curve and decided to up the preload and delay secondary engagement some more

Secondary now engagement now at 26 degrees (10btdc) with more preload

The 7.1 curve did what I expected, slight delay in start, and didn't flatten out as much up top (look at distance between 7.0 & 7.1 at top )..


Test 7.1
10 degrees initial
no ping

Test 7.2
12 degrees initial
some hints, but it was hard to tell

Test 7.3
14 degrees initial
yep, it's pinging



I think something strange is going on down bottom though............

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

I'll try to explain this a succinctly as possible....

Facts: (i'm really really sure)
1. As the weights move out, there's also a sideways movement that rotates the cam/reluctor piece
2. You can rotate the cam/reluctor piece to move the weights out
3. To some degree each spring sees both weights because of the interlinked nature of the setup.

Now look at the picture below:
The pink and yellow are the actually curves, the other 2 curves are what I think the curves should be. I looks like there is a delay in the advance, then it catches up and falls on the curve (more delay on yellow which has more preload)

Surmises: (I'm partially sure)
1. I think that with asymmetric springs (either different rates/preloads or different engagement points) the weight with the least resistance (preload & rate) tries to advance the cam. The weight with the most resistance holds it back. With a greater difference in preload/rate, there is more binding of the mechanism. Thus the advance mechanism sticks closed until it finally can overcome the sideways friction. (yellow curve bows more than pink curve).
2. The stickiness of the mechanism is more likely at the lower end due the geometries of the weights and pins.

Anyone else ever see this??????

I think in my effort to get to 12.5 degrees initial timing, I'm to stiff on one side, and thus the bowing

Test of surmises
Surmise 1. It actually looks like I don't need a 2-step curve, so I'll split the load into 2 springs of about 30lbs each. and see if the bow goes away.
Surmise 2. I can't test this, but if someone has multiple cam/reluctors available, I'd be curious if longer slotted cams have the slot grow out towards the outside, the inside, or both ways. If it's to the inside, or both ways it would be possible to test if a asymmetric preload has more of an effect on the cam/reluctor that starts closer to the center.

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

hey ed

IIRC, Slant six dan told me that american dists had a linear slotted dist govnor. Down here in argentina we have a slanted slot govnor that helps out big time to "straigthen" the curve, as it's slotted to the outter side (right) of the govnor on each "arm". This way, when the weights starts to move, the leftmost wall contacting the weight's pin actually reduces friction and facilitates the motion instead of producing drag like the regular nonslanted slot.

here goes a pic:



recurved

original thing.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Out of about 10 that I have seen (in person) various years and advance amounts ( all labeled 9, 11 or 15 ), they have all been straight slots.

Sounds like you need to have parts shipped in from argentina.

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1980 Aspen 225 super six

Hi Guys:

Friction is a killer in distributors, especially for the weights to return to "zero" with lighter springs.

Most of my experience is with GM distributors, but I've built at least 50 Mopars over the years. I like certain things about them alot, but some things not so much. I have much more lee-way to curve a GM because of the cam/weight interface design (point style usually converted with Pertronics...I hate the HEI distributors), you can tailor the curve by changing the leverage the weights apply to the cam by grinding...thus getting a wide range of ability to tailor the curve linear or non-linear.

That said, to answer Kesteb's question, the only way I know to get a non-linear curve with Chrysler is the way the factory did it with springs that have an extra long "hook', so that the spring doesn't have an affect until the weights have moved out some amount which can be tailored by bending the spring.

Here is a pic:



You must be careful though, because using this method will leave you only one spring to close the weights back at idle...so it is a fine balance between how light a spring to get the first few degrees quick, and still overcome friction on the way back.

Another solution might just be to run more initial (I run 17-18 degrees) and then have a stiff linear curve that doesn't start to engage until you are out of your pinging range of rpm.

emsvitil...keep up the good work...I wish I had more time to help, but its going to take all my time to keep my own threads going.

Go around to some old garages that are still going, or even old machine shops, especially in small towns, often you can find perfectly good distributor machines covered in dust in the corner of a shop and get them for $100 bucks...well worth having in your garage. I've bought four over the years and paid $100 twice for different Allen machines, got a pretty thrashed for parts only Sun machine for free...and of course, my nice neighbor just gave me my best one last year.

I've past on a few, one off brand but really nice one...but the guy wanted $500, typically swap meet guys think they have a treasure. Some of my friends have done just what I suggested and found machines themselves.

If you ever do decide to buy one, don't worry about whether it can do electronic...it is super easy to make electronics distributors work...just use a 12v wall wart power supply and the factory ignition box. I have a wrecking yard Mopar box mounted on my machine that I use for all reluctor type distributors except HEI's because they have the module built in. Pertronics types, just hook 12v to the red wire, and the black to where the points would normally connect to the machine.

Many of the machines have built in vacuum pumps, but if the diaphram is bad (usually) I just use the trigger type you get at the parts store...

Later

Gearhead

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"