GM distributor

[Bill S]

Thinking about putting a GM distributor in a 50 Ford with a stock V8. Seen some threads about using vacuum advance and some using mechanical for the advance. Any ideas which is best?

Thanks

[ken ct]

Contact Charlie,NY on here ,he modifies them for flatheads. ken ct.

[Dale Fairfax]

Your stock distributor has a system called "Loadamatic" which is entirely vacuum operated and is widely known to be a poor concept. The GM conversions use a distributor which has a mechanical advance supplemented with vacuum. The combination is a much better system and will improve the performance of any '49-'53 Flathead. GMC Bubba, who posts here frequently, is the "go to guy" for these conversions.

[BUBBAS IGNITION]

Bill,
This week we shipped our chevrolet conversion # 704, cant believe we have done over 700 units in approx 4 years. Out of the 700 approx 20 have had vacuum advance .
Theres no doubt that the adjustable vacuum advance will give the car some additional miles per gallon , however its kinda hard to tune on the flathead.
Richard here on the barn has been very successfull working with ole Ron and getting the vacuum unit working .

The concept of having both vacuum and mechanical advance is a good idea as it keeps the advance up most of the time when the engine is running. The vac and mechanical overlap each other . SO if you have a vac can (lets say 7 degrees or 14 degrees engine) and a mechanical advance of 18 degrees engine. It would appear that we have 14 plus the 18 for advance or a total of 32 degrees.
Thats not the way it works , lets say we want 16-18 degrees of advance in the engine (based on the design of the flathead, the valve placement the exhaust flow etc) if the engine was ran wot the mechanical advance would supply 18 degrees and the vacuum would be so low that it wouldnt add anything to the number.and the engine would run properly (very well).
Now let off the throttle and lets say the mechanical advance dropped 1/2 of the 18 degrees to 9 degrees based on the lower rpm. The vacuum would increase to 9 degrees based on the increased vac and we still would have 18 degrees of advance . So in this manner would would always have what we wanted ( again based on design of the engine) as long as the engine was running.....

Thats the way it works , one goes up the other goes down ......
So got some time then use ( and tune) the vacuum.

[Ol' Ron]

Soo JIm you have 680 customers getting lozy mileage?? Actually the engine spens 90% of it's time at part throttle, so adding the vacuum advance will operat when the Power valve is closed to run a lean mixture. Bubba waz shipping his distributors with 24 degrees advance without the vac adv. This works wekk and is something MSD and Mallory do to. However the flathead is a LOW compression engine and this much advance diesn't hurt much especially if it comes in at a higher RPM like 2500.

I started converting GM distributors back in the 80's and some guys were doing it long before that. Very few of us used the vacuum canester, we felt it wasn't necessary. Back in 2002-3 I built a 296ci engine for an engineer working for P&W. I furnished a GM dist. He asked where the Vac adv was I said he didn't need it and he told my in a very polite way I waz full of sh*t. He sent the dist off to some guy in Ca. and he cinverted it to electronic and added the vac adv. The engineer began tuning the ign and carb and was getting over 20 mpg with a C4 in a 3200 lb truck.
It was about that time I realized that my racing back ground was causing these street engines to be washing their cylinder walls with un burnt gas during cruise.
We learn sumpin every day. Too soon old , to late smart I know there many barners that find tuning there engine part of the fun. My test engine is almost ready for its maden voyage, be interesting. I'm going to need drivers so in you show up you might become the daily driver.

[Richard in Florida]

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The vacuum [advance] would increase to 9 degrees based on the increased vac and we still would have 18 degrees of advance. So in this manner would would always have what we wanted (again based on design of the engine) as long as the engine was running.

Not exactly... not in all cases.

We made some data runs while monitoring the manifold vacuum and the amount of vacuum advance in real time, recorded on videotape as I drove around. With a standard adjustable vacuum canister set for 6 degrees, it was clear that all 6 degrees of vacuum advance were nearly always fully in effect.

This was true at idle, light acceleration from a stop, moderate acceleration while cruising, and steady-state cruising.

The only time the vacuum dropped out was at WOT, when it should. There were no real periods of partial vacuum to speak of.

The other benefit of vacuum advance is that it kicks in during idle because the vacuum is high then, too. The increase in advance during idle results in smoother, cooler running.

[40 Deluxe]

Richard, have you run any tests using ported vacuum instead of manifold vacuum?

[Ol' Ron]

This would be difficult to tune when running a long cam, such as the L-100 and is best left to factory engineers. Most flatheads have multiable carbs and using manifold vacuum is more accurate method of measuring load.

[George/Maine]

I have a loadomatic on my 51 mercury engine.When i timed it i hooked up vacl line and was no different at idle.
I marked 1 " and 1 1/2" just to see how much it moves.Rev up moves 1 1/2 max.
Like vac wipers they must stop,or retard when going up hill.
My problem going up hill the engine runs hotter.I,m geared to run 55 at 2000 rpms.
Now full advance with mechial advance is set at 2500prms,it would be less then full.I think Ford wanted full at 2000.
Now if at same speed and no retard from vac,would i run cooler or same temp.
If a old chevy ponts dist was used, could one be made for flathead,they were good and not big like hei.

[BUBBAS IGNITION]

Originally Posted by George/Maine

I have a loadomatic on my 51 mercury engine.When i timed it i hooked up vacl line and was no different at idle.
I marked 1 " and 1 1/2" just to see how much it moves.Rev up moves 1 1/2 max.
Like vac wipers they must stop,or retard when going up hill.
My problem going up hill the engine runs hotter.I,m geared to run 55 at 2000 rpms.
Now full advance with mechial advance is set at 2500prms,it would be less then full.I think Ford wanted full at 2000.
Now if at same speed and no retard from vac,would i run cooler or same temp.
If a old chevy ponts dist was used, could one be made for flathead,they were good and not big like hei.

George ,

Thats pretty typical for the loadamatic distributor. I would first try a new vacuum diaphram from Mac Van Pelt and see if that fixes the problem, assuming you are not running a radical cam and multple carbs the load amatic will fix the problem.

We do the chevrolet conversions (the chevy v8 distributor was one of the best ever made )and a typical unit is 18-24 degrees at 2500 rpm with no vacuum needed, straight mechanical.

Many of our customers have noticed the engine runs cooler with the mechanical advance.

As a Ford Barn experiment i would be more than happy to ship you one to try as a experiment ...just let me know...

[Ol' Ron]

Jim
In this case with a stock engine using an advance curve of 24 degs at 2500 RPM. THis should work quite well. I'll have better knowledge of this when the test engine is in the road. However, you'd never get away with that curve in Richards engine. His adverage cylinder compression is over 170 lbs and that's with an L-100 cam. This concerns me when running a milder cam in a big engine. Richard can record the timing on vidio at all speeds and loads including A/F and vacuum. This new system is just being put into use now, and should give us a better look of "what's happining".
Sending that guy a distributor is a great idea, keep up the giid work.

[GOW]

i've got a stock 50....i just put a petronix conversion and coil on the 50. it seems to run smoother in 3rd gear and the temp has gone down a few degrees.....I THINK !!!!!

[Cecil/WV]

I've run Pertronix on my '50 Ford for 10 years and it has always had the spark breaking down at high RPM, above road speed, until last week when it starting breaking down and affecting the normal operation. On last Wed., I installed another distributor with point and condensor and it runs well.

Last week, with the Pertronix, letting the spark jump from a wire to the head bolt, the higher the RPM, the closer the wire had to be to the head until it was against the head, however, the spark was still a crisp, blue spark, it just wouldn't jump as far.

[Bill S]

Thanks Guys for all the input.

[Richard in Florida]

Originally Posted by 40 Deluxe

Richard, have you run any tests using ported vacuum instead of manifold vacuum?

No, all of our tests were done with manifold vacuum.

[40grit]

I know I am resurrecting an old thread but just put the first 50 miles on a sbc distributor in my 51 Merc engine. I got the distributor from Charlie NY because I really wanted to run a vacuum advance unit. The unit arrived quickly and more importantly works great. The advance curve appears to be "right on". My personal opinion is the vacuum advance is well worth the effort in promoting better mileage and a cooler running flathead. Thanks Charlie.

I am a happy camper.

John L

[Wily Kyote]

A real car guy's mission: Correct one of motordoms longest standing errors...

1) Bribe the missus into just one more favor. "Can I buy an old car, Hon. Can I? You can go ahead and get the new carpet you've wanted... Pleeeeeaaase...."

2) Borrow all that your banker will loan on the ranch.

3) Search 'Old Cars for Sale' ads for weeks... maybe months.

4) Buy an 49-53 Ford or Merc.

5) Polish. Tune. Cruise with the locals. Tune some more.

6) Install a modified used-to-be SBC distributor.

Jeepers, what lengths some guys will go to, to mount a SBC distrbutor up front where it belongs.

[Charlie ny]

Bill,
There is a bunch of technical reasons...can vs no can. In simple terms the
vac can seems to make the motor run smoother....in a test for my own edification
I tried one of each that I build in my fairly warm street 8BA....I'll go with the vac
can. My curve is 20 degrees mechanical with 5 degrees initial and an off the shelf
can from Carquest. I found I could run more initial with the can than without. When
I pull a long hill ( my test hill ) I get a nano second ping when my motor starts to
work with the can. Without the can the ping is light but persistant with the same
initial setting....and that's my story.
Charlie ny

[Ol' Ron]

Satire is great. But the truth here is: the original Ford Load-A-Matic, even in perfect operating condition. Does not work as well as the distributor it replaced. The fact that the GM distributer eliminates these problems, is benifical to the owners of these cars.

Now, not to date myself, but back in the 50's they modified Studabacker distributors Units??

[Charlie ny]

Ron,
Speaking of Studebakers....there was a '37 Ford barn find coupe with a 239
under the hood on the GREEN field. That particular 239 was a late 50's Studey ohv V8 with 2 2's. I thought a sbc looked at home under a Ford hood...that Studey was even
more perfect.........$22000 I don't think so. Of course nothing looks as good as a
Flathead under the hood.
Charlie ny