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MM Uni Tractor V4 Distributor cap


 
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Bozrae1617
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PostPosted: Wed Jan 12, 2022 6:17 am    Post subject: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

Trying to find the correct distributor cap for an MM Uni tractor with the V4 206 engine. The original distributor cap was lost and while another Delco cap will fit, the firing order on the distributor cam lobes for the points are not spaced an equal 90 degrees all the way around. A normal distributor cap has the plug wire outlets spaced at an even 90 degrees apart. This was discovered when setting the valve lash. The pointer on the distributor only lined up correctly with the replacement cap in 2 locations when the piston was on top dead center during compression stroke. The only way I can see this working correctly is with a special distributor cap. Attached are some pictures taken from the MM service manual showing the distributor cam rotation angles and the part #s for the distributor. If anyone may have the correct cap or any additional information, please let me know.
Thanks, Steve
The MM distributor part# is: 10B1989 and the Delco-Remy # is: 1111559


 
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wore out
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PostPosted: Wed Jan 12, 2022 10:02 am    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

[quote="CVPost-Bozrae1617"]

Odd-fire Wisconsin V-4 engines solve the problem you are seeing by using a rotor with a WIDE outer tip along with a "normal" distributor cap.

I suspect that may be what MM did?



Wisconsin rotor, won't fit yours, though, as it is for a Prestolite distributor, so far I haven't found a similar Delco.
 
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T.R.K.
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PostPosted: Wed Jan 12, 2022 5:30 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

The Distribuitor cap was the same Delco cap as for the ZA, ZB, U, 445, etc. The 'real' issue is do you still have the rotor button? I had to re-use the old one when I got my Uniharvestor running back in 2001. The rotor button has a curved wing on it so some part of the wing is close to the post in the cap when it does the odd-fire thing. (Kinda like 'wore out's picture, but a Delco style button.)

I recall that NAPA had a Delco rotor button with a wing for some kind of Allis Chalmers tractor back then, the wing went the opposite way off the rotor button.

You probably already know this, but the Distribuitor in those V engines has to be exactly timed to the cams. No 180 degrees off and it'll still run stuff.
 
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Bozrae1617
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PostPosted: Thu Jan 13, 2022 5:03 am    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

Thanks for the replies. I didn't realize the rotor may be somehow compensating for the odd firing sequence. I don't yet understand how that would work, but maybe if I seen the correct rotor it would make sense. The Uni is not at my house, but I will check it out in a day or two to see what rotor it has on because I don't recall what it looks like.
A little history on the machine; I'm part owner with a friend, we purchased it about 10 years ago and harvested a few acres of corn each year with it. It was running when we got it, although to me it didn't seem like it ran 100% correctly, but I've never heard another one running so maybe it was normal. It seemed to make adequate power for what it needed to do. About 3 years ago it developed a miss in the engine while harvesting with it. New plugs, wires and distributor cap where put on the machine. Don't know if the rotor was replaced, I wasn't there at that time. It didn't fix the miss firing cylinder however. What it ended up being was a broken exhaust valve spring. That head was pulled off and and valve job was done. The odd firing rotation was discovered when setting valve lash.
 
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T.R.K.
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PostPosted: Thu Jan 13, 2022 6:17 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

Its been over 20 years since I had mine running. As I recall, even when everything is running right they don't sound like an in-line four cylinder MM. The v-4 does sound best however when it is at governed throttle/fast idle or whatever you want to call it. the extra throttle shaft in the manifold just slows it down some, kinda like some of the MM power unit governors.
 
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Al nickel
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PostPosted: Fri Jan 14, 2022 8:23 am    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

I do not understand how a 4 cylinder engine can run properly with distributer contacts not exactly 90 degrees apart
Can someone explain this ???
 
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wore out
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PostPosted: Fri Jan 14, 2022 9:15 am    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

CVPost-Al nickel wrote:
(quoted from post at 09:23:33 01/14/22) I do not understand how a 4 cylinder engine can run properly with distributer contacts not exactly 90 degrees apart
Can someone explain this ???


It is a V-4-engine, the combination of the arrangement of the crankshaft "throws" and the degrees of the "V" of the block cause the various pistons to reach TDC at uneven intervals, the camshaft is "ground" to make the valves cycle accordingly, and the lobes in the distributor are unevenly spaced so each cylinder fires in a corresponding manner.
 
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Tramway Guy
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PostPosted: Fri Jan 14, 2022 8:09 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

And to make things even more frustrating, there is NO electronic ignition kit from Pertonix that works on an Odd-fire V4 engine. You are limited to points only.
 
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Tramway Guy
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PostPosted: Fri Jan 14, 2022 8:14 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

The crankshaft is made with only two throws at 180 degrees apart, and both crank journals are shared by a cylinder on each bank. Its like two John Deere engines at 90 degrees off.

To have an even-fire V4, you need to have a crankshaft with four separate rod journals.
 
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molinegb
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PostPosted: Sun Jan 16, 2022 5:20 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

MM made a V4 for Uni's. It used Z blocks and pistons. Later used overhead. 445/Jetstar blocks heads. Both were 206 cubes. Not many here. Have seen few in SK.
 
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Bozrae1617
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PostPosted: Mon Jan 17, 2022 3:57 am    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

Was able to get over to the UNI this weekend and see what rotor it had on it. It looks to be just your standard rotor. Not sure how long that one has been on there. I understand now how a rotor similar to the
one in the picture that 'wore out' posted will work. Just need to find a Delco version of that or try to modify an existing rotor. The UNI we have is the valve in head version, with heads like the 445 etc.
Here is a picture of what is currently on the UNI. Thanks for all your help and comments everyone.

 
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Tramway Guy
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PostPosted: Mon Jan 17, 2022 2:41 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

Maybe you could find an 8-cylinder distributor that would fit mechanically. Then just use the appropriate terminals for the odd-fire engine. Ground the unused terminals, maybe?

The body and cap would necessarily be larger, but it might work.
 
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Tramway Guy
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PostPosted: Mon Jan 17, 2022 2:48 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

Scratch that idea. Youve got a 60 degree and 120 degree mixed in with the 90s. More like a V12 distributor. It has 12 terminals at 30 degrees apart. Probably harder to find than a special Delco rotor.
 
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Tramway Guy
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PostPosted: Mon Jan 17, 2022 3:11 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

The Buick v-6 odd-fire engine used a rotor similar to the auto lite
one you showed in the photo. Had a trailing clip at the end.
Maybe this one?

 
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wore out
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PostPosted: Mon Jan 17, 2022 3:27 pm    Post subject: Re: MM Uni Tractor V4 Distributor cap Reply to specific post Reply with quote

I looked at some older Ag and Industrial ignition info and the only thing I could come up in Delco with was the rotor shown below. It is only extended in one direction, and I don't know if it would work for your engine.

I have a distributor machine and have cut holes with a hole saw in spare caps and run a distributor on the machine, you can then see where the rotor tip is in relation to the cap terminals when the points fire the coil.

As a last resort if you can't solve this locally, I would be willing to do that for you and possibly modify the rotor as needed.




ONE place to buy the Deloc rotor

 
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