Model B Distributor in a Model A

[JimZ]

My ‘31 coupe came to me through my dad beginning with my grandfather’s purchase of it in 1934. At some point in the past 90 years the original distributor was replaced with a model B version. As far as I can tell everything else on the engine is 1931 Model A. It runs pretty good with the timing set by ear but I would like to attempt to set it to some kind of specification to achieve its full running potential.

Can anyone give me information or identify a previous post on properly setting the timing of a Model A with a Model B distributor? Thanks!

[Patrick L.]

It'll depend on the timing cover, they are different. If you could post a pic of the timing pin boss. If it's a B cover then set it just like an A. The timing should be advanced more.

[jwmckenzie]

The Model B is timed at 19degrees BTDC.

If you have a Model A timing gear cover, the crankshaft has to be backed up 19degrees, after the pin drops in the camshaft gear.

If you have a Model B timing gear cover, rare. The pin will drop in at 19degrees BTDC.

[Jack Shaft]

Or you can use a pointer and mark TDC, then you can use a timing light.You can buy a degree scale or just use your eye,5 degrees advances is 1/4" at 500 rpm...the engine likes 1 degree of advance per 100 rpm max at 24 degrees.by rigging a tach dwell meter and using a timing light you can 'map' the advance...5 degrees at 500,10 degrees at 1000,ect..

[JimZ]

I think the cover is a Model A. I will follow your instructions. Thanks very much!

[Ruth]

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Originally Posted by Jack Shaft

Or you can use a pointer and mark TDC, then you can use a timing light.You can buy a degree scale or just use your eye,5 degrees advances is 1/4" at 500 rpm...the engine likes 1 degree of advance per 100 rpm max at 24 degrees.by rigging a tach dwell meter and using a timing light you can 'map' the advance...5 degrees at 500,10 degrees at 1000,ect..

Jack, you mention a dwell tach. Do you happen to know the dwell setting that would equal the points set at ~.020"?

Someone on Ford Barn suggested a setting but I can not find it now. I thought I would try setting my points with my dwell tach.

[bruceincam]

Originally Posted by Ruth

Jack, you mention a dwell tach. Do you happen to know the dwell setting that would equal the points set at ~.020"?

Someone on Ford Barn suggested a setting but I can not find it now. I thought I would try setting my points with my dwell tach.

The dwell for a four cylinder at 0.020" point gap should be 30 deg. or so. Low 30's should be the expectation.

[Ruth]

Originally Posted by bruceincam

The dwell for a four cylinder at 0.020" point gap should be 30 deg. or so. Low 30's should be the expectation.

Thanks Bruce. I seem to remember the other member mention he found 32° was optimal but I was not sure. Thanks for confirming that to me.

I'll write it sown this time.

[ursus]

Originally Posted by bruceincam

The dwell for a four cylinder at 0.020" point gap should be 30 deg. or so. Low 30's should be the expectation.

The OP says he has a Model B distributor. If it has the Model B cam, then the dwell should be 42-43 degrees. The stock Model A distributor cam will have less dwell, at 32-33 degrees. Many are now using the improved Model B cam and it seems that may be all that the vendors now sell.

[Ruth]

Originally Posted by ursus

The OP says he has a Model B distributor. If it has the Model B cam, then the dwell should be 42-43 degrees. The stock Model A distributor cam will have less dwell, at 32-33 degrees. Many are now using the improved Model B cam and it seems that may be all that the vendors now sell.

Well, ya see. That's where I was confused. I have a B distributor cam so I'll try 42° then check the gap. Thanks Ursus.

[JimZ]

How can you tell if you have a Model B cam without pulling it out?

[Greg Jones]

I think we are talking about the distributor cam, the thing the point open and shut against. Or at least I think we are.....

[JimZ]

You’re right, sorry.

[Charlie Stephens]

Originally Posted by JimZ

I think the cover is a Model A. I will follow your instructions. Thanks very much!

Model B cover with pin at top of elongated boss for comparison.

Charlie Stephens

[Charlie Stephens]

Originally Posted by JimZ

My ‘31 coupe came to me through my dad beginning with my grandfather’s purchase of it in 1934. At some point in the past 90 years the original distributor was replaced with a model B version. As far as I can tell everything else on the engine is 1931 Model A. It runs pretty good with the timing set by ear but I would like to attempt to set it to some kind of specification to achieve its full running potential.

Can anyone give me information or identify a previous post on properly setting the timing of a Model A with a Model B distributor? Thanks!

Another handy thing if you are looking for a condenser for the B distributer buy the best Model A condenser you can find from a place like Bratton's. Elongate the hole on the bottom and add a short wire as in the pictures.

Charlie Stephens

[JimZ]

I backed up the crank 19 deg from tdc, set timing with method using a lamp attached to hot side of points and ground. It ran terrible and with backfire upon acceleration. Reset to previous setting with #1 at tdc and it ran ok again.

Is it possible I have an auto advance breaker plate and a Model A distributor cam.

[JimZ]

Also, gap between rotor and distributor pin is .040. This sound correct? The rotor photo is positioned just prior to points opening timed with #1 at tdc. Does this look correct.

[Russ/40]

Rotor to pin should be .025" That is a "B" distributor.

[JimZ]

Any idea why my gap there is too large? Neither the rotor nor cap is burned or worn to the amount of .015. Likely poor quality aftermarket parts?

[Greg Jones]

In my experience, rotors are never ready-to-go out of the box. If you find one that is, you just got lucky. You almost always need to tweak this clearance. By this I mean you may need to judiciously bend the end of the rotor tab either up or down to adjust the clearance. Sometimes, I have had to do some slight filing on the contacts in the distributor cap to get the 0.025" (or close to it) gap consistently on all four points. Most times on new parts, I have to do both. Make sense?