The Stovebolt Site Forums The Shop Area The Electrical Bay Dual Point Distributor

Never had the opportunity to work on a vehicle with a dual point distributor. Have a 1953 one ton Chevrolet with the 235 six that has a later dual point MSD distributor in to.

What's the best way to set the dwell? One set at a time by insulating one set off? If so, what is the best dwell angle to shoot for?

Dual points are double trouble! Unless you're racing, it's just too much trouble to run a dual point distributor. How many lobes are on the cam? Some 6-cylinder dual point systems are also dual coil, with only 3 cam lobes, and 3 cylinders run off each set of points. If that's the case, there will be an oddball distributor cap with two coil wire towers, and a dual-plane rotor.

The more common setup is a leading/lagging point system where one set of points closes before the other, and the second set of points opens a little later. That allows you to have a longer overall dwell setting than is possible with single points. Start by setting both points to the same gap, maybe .020" for instance, and see what the total dwell angle is when measured at the coil side of the distributor with the engine running.

A 6 cylinder distributor fires a spark plug every 60 degrees, and normal dwell is 66% of the total available, or a maximum of 39.5-40 degrees. A dual point setup might allow 45-48 degrees of total dwell without getting the point gap so close the primary induction causes a flashover. Start by putting a piece of paper between one set of points and adjusting the other set to 35 degrees, for instance. Then isolate the points you just set, and adjust the second set just like the first. Then run them both together and check total dwell. Increase or decrease individual dwell settings until you get the overall dwell you want.

The leading point will start the current flowing in the primary winding, and the lagging point will break it. The spark will happen when the lagging point breaks. Have fun!
Jerry

I have a couple of GMC's with dual points, but they were conversions. I make sure I keep plenty of lube on the cam so the rubbing blocks so they say put. I also have a 56 Ford with a Holley dual point. Its even worse because the distributor on a Y-Block is on the back of the engine. I used to set them at a dealership that had a Sun distributor machine. The dealership closed and they had an auction while I was in Europe visiting my wife's family. I wish I could have bought the machine.

It came in this way,so I guess it stays this way. It isn't mine to change. I'll see if I can set the dwell better, or least the air gap.

This has the single coil, and one set leads the other.

My next question was going to be how much overall dwell with both points working so I could shoot for that.

Thanks. I really can't see the advantage of this type point set up on a daily driver truck.

Cren, my grand dad had a 64 F... with the 292 Y-block. It was a pain in the rear to work with the distributor.

I've got a Sun distributor tester that's in need of a cleanup and general overhaul. The item that fails on them pretty regularly is the Xenon flash tube that illuminates the rotating arrow every time the points break. I use a delay-flash Snap-On timing light to locate the arrow instead of the internal flash tube, since the only employee Sun had who could build the flash tubes properly died back in the 1970's!
Jerry

I got married in a 56 Ford. https://plus.google.com/photos/1081...1431006034&oid=108197707187186692269

I now have 4 of them, but I have a dozen GMCs.

Hey Crenwelge, I got married the first time in a 53 Ford 2 door hardtop. The second time in a 68 Chevy Impala and the third time in a 2000 GMC. Maybe this one will work.......
BTW, so as not to get off topic. That point cam lube in the little capsule, my Grandpa said you take that to calm your nerves before installing a new set of points.