Autolite dual point ignition

[avantey]

Where can I find information on setting the timing on a dual point distributor? My 1931 Hupp model L has a positive ground, dual point Autolite distributor in it. I have many Hupp Service Bulletins, owner's manual, MOTORS issues 1948 and 1964 but none cover this.

While firing it up for the first time in three years I mistakenly loosened and moved the secondary plate as I tried to adjust the secondary points gap. I returned it to approximately the previous position (by the visible dirt/oil ring from the plate edge) and the car eventually fired right up. It seems to idle OK but a little rough when I revved it up a little. I could not drive it to get a real road condition check as it is off the road for now.

How do I know the position of the 2 plate is correct? I think the theory is to open the second points with an overlap to the first points to prolong the spark duration. Is that correct? Where is the spec and how do you check it? With a dwell meter or a scope or ?

Also the primary points gap did not seem to adjust readily to the adjuster cam screw. Full motion in either direction barely seemed to change the gap which looks a little too small. It checks at .014-.015 when the spec says .019-.022. I had both lock down screws loose but it barely moved the gap.

I am also about to send this engine out for rebuild so I would be reinstalling the distributor in the spring and need to know for that too.

Thanks for the help,

Bill

[avantey]

I just went to the garage and checked the distributor. The data plate has two fields- one is stamped "GH4008C", the right side is "6K". Does this help?

Any leads on this would be appreciated. I have never dealt with a dual point before, my Avanti is supposed to be but my father replaced the distributor with a single point shortly after he got it. Too much trouble to keep timed apparently!

Thank you in advance-

[jrbartlett]

You need to say how many cylinders your car has, and how many lobes are on the distributor shaft. In some cars -- my '35 Auburn is one -- one set of points fires half the cylinders, and the other set fires the remaining cylinders. It's an 8-cylinder car with 4 distributor cam lobes.

I assume the purpose is to reduce wear/burning/pitting on the contact faces.

I've replaced the points several times without worrying about the timing, since I had no easy way to check the second set of cylinders. One time I took the distributor out and had the relative timing between the two sets of points set precisely on a Sun distributor tester. An old timer was familiar with such systems. But I noticed no difference in how the car ran compared to all the times I just replaced the points without worrying about it.

At one time I fitted electronic ignition to the distributor, with an eight-lobe sleeve that fit over the original shaft. Again, I could tell no difference in how the engine ran. The ignition burned out after only two years, and I couldn't get replacement parts, so I went back to points and have been happy with them since.

Someone else can weigh in on how to set points when both operate simultaneously. I suspect they should open at precisely the same time -- unless you have dual spark plugs. On my Locomobile -- 6 cylinders with 12 spark plugs and dual distributors -- one side fires slightly later than the other.

[avantey]

Thank you James. It is a straight 8 engine. The dist is a 4 lobe cam, CCW rotation with about 240 degrees between point sets (in the direction of rotation).

I had not thought about the idea of four cylinders for each point set. Somewhere in my limited knowledge I had heard dual points ran in timed tandem for every cylinder. It sounds similar to your Auburn.

Thank you!

[startergenrebuilder]

According to my books:

"Synchronizing: Moveable points open 45 degress after stationary."

The best way to set it up without a sychronizing tool is to have it run on a Sun Machine. I can do this for you, but you might know of someone closer just to get it set up. I sychronize them after rebuilding them. Let me know if I can help you at all.

Jason

Advanced Electrical Rebuilders

www.aerrebuild.com

[avantey]

Thanks Jason- is that a generic set up for all dual points? V8 and straight 8? I am confused a little now. The car is running great right now but the secondary points are not 45 degrees after stationary. As I stated they are about 240 after stationary in rotation.

45 would make sense on an 8 lobe cam since that is the lobe separation. But they would be physically very close in the dist body wouldn't they? Now 225 is 180 plus 45 and I only eyeballed the angle but that would give the physical spacing needed and meet the 45 degree criteria.

I guess I need to crank the car and see if they open sequentially or in timed unison. James' theory makes some sense to me with the straight 8 and a four lobe if matched to the firing order.

This is getting interesting! I am learning (AGAIN) on this forum!

Thanks-

[avantey]

Jason- I just looked at your website. Well done and you seem to have expertise here. Can you explain the 45 degree set up any better? And the sequential vs in timed tandem to extend the dwell and spark duration?

I am really just trying to learn now! Or to my original quest- where can I read up on this?

Thanks again-

[startergenrebuilder]

The 45 degree is not a generic setting for all dual point distributors. I have a '36 Packard V12 distributor in the shop now that has a 33 1/2, 26 1/2, 33 1/2, etc. degree interval. They use to offer a synchronizing guage for each particular distributor, but they have long disappeared. Other than the data, I don't believe I have any good reading material for you.

Jason

Advanced Electrical Rebuilders

www.aerrebuild.com

[1937-44]

According to my Motor's manual as I understand it:

With the spark fully advanced, crank the engine until #8 piston is coming up on it's compression stroke. Stationary points break when the line about 2 1/4 inches before the 1-8DC mark on the flywheel lines up with the center line of the peep hole in the flywheel housing. Loosen the adjustable breaker arm plate screws and turn the adjusting screw until the adjustable set of points open.

[Owen_Dyneto]

For an 8 cylinder engine with a 4-lobe distributor cam, each set firing 4 cylinders, this may give you some ideas on how to synchronize the points in the absence of a Sun machine.

PackardClub.org • View topic - Synchronizing NorthEast dual points

Edited November 18, 2011 by Owen_Dyneto (see edit history)

[Friartuck]

Bill,

I believe the intent behind the dual point arrangement was to allow more time for the coils to reach maximum field strength (called saturation). It was believed that dividing the 8 cylinders up into two banks of four accomplished that. On my model L Lincoln, they used one set for the left bank of cylinders and the second ignition set for the other on their V-8. Again for Lincoln, there are timing marks on the flywheel for each set (R1 and R2). Using a simple Ohm meter-continuity tester, when the flywheel passes the respective mark is when the points are supposed to open (this is also called a static method). Look for marks on your flywheel to see if that is how Hupp did their timing (and possibly the valve timing as well). Let us know the results.

Chris W.

Edited November 18, 2011 by Friartuck
typo (see edit history)