ZA engine design

bcny

Member
Tell me I wasn't dreaming. Some time around 1977 I worked on a tractor, I think a ZAU,
the construction of the engine was different.
I remember bolt on cylinders. Blind bored (not not bored through). The valves were overhead
in the sense they were entirely above the piston. But they were horizontal. Activated by a long rocker
arm that reached down to the cam? And the head was like a flat head, just a cover, but 90 degrees from most engines.
Can't remember much about the manifolds. Can anyone straighten me out. Was this a good engine-economical,long lasting?
Want insight.

Thanks!
 
ZA/ZB same design as ZT or RT dating back to 1937. All same 3 5/8 bore but different stroke. My research found to be a German design. One promotion was it could be rebuilt sitting on a milk stool.
 
The engine uses walking beam valve rockers. This design was produced by the Duesenberg Brothers for use
in racing cars and in airplanes during the 19-teens. I saw one on display at the Indianapolis 500 museum.
They also designed engines for the Maytag cars, and also for speed boats. They got contracts from the US government to build licensed copies of the Bugatti aircraft engines in WWI. When they started business, they were located in
St. Paul, MN. I don't know if they helped Minneapolis Moline, but maybe.
 
If you'd like I can send you some pictures of a cut-a=way engine I built out of scrap parts in 1990. Send me an email, I haven't mastered putting pictures on here yet
 
Just go to bottom and choose files then add. Will appear as Jpg -- etc and you can preview before submitting. I believe is Mercedes design.
 
Something like these TOO small pics?
The Duesenberg patents.
GB, can you corroborate my thinking for the Z engines having 140 less parts than a regular I-head engine?
Less parts yes but is my memory on this junk?
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This post was edited by Duey C on 05/26/2021 at 10:08 pm.
 
Wow, with your replies, looking at the AGCO parts books and a few YouTube videos,
I got to say it was as weird as I remember. The crankshaft has plain center bearing and rear bearing,
but the front was a ball bearing? Or did they have some models with plain front bearing also? Look at that unique rear main bearing carrier!

I opened the parts book for 445 tractor's engine. A massive redesign from flat head to OHV. Push rods, no more giant rocker arms. Still bolt on cylinder jugs.
There is a good set of YouTube videos on rebuilding the 445 prototype machine.

If you could, some comments on the effectiveness of this design. Did they hold up well?
 
Compared to a later 206 MM ohv would be few parts less like 8 lifters 8 pushrods and 1 head. MM had similar motor with hydraulic
lifters in OEA motor. Used mainly in NTX.
 
I Think of those as pretty robust engines. I have seen two still would run with .019 clearance in the rod bearings. (I didn't them it long.) I think I have 5 of them sitting here.

The front roller bearing in the 206 was kept until MM re-designed the 206 into an overhead valve engine in the latter part of the '50s. Then the front main was the same size as the center main.

There were at least 3 versions of that L-Head engine:

The RE which (I think) had ball bearings front and rear and just a floating sleeve feeding oil to the rod bearings. Used in the ZT tractors. 185 cubic inches.

The EE engine which used the front roller bearing and an insert rear bearing with no connection at the center of the crank. Oil to the rods was fed to the rear main bearing and distribuited through the crankshaft passages. 165 cubic inches.

The 206 engine which had the roller bearing at front and a plain center and rear main bearing. 206 cubic inches.

All three engines used the same bore, but rods were different lengths and piston deck heights were different.

After that the 206 was re-designed with overhead valves and all insert bearings on the crankshaft. There were als a similar overhead valve engines that had 165 and 220 cubic inch displacement. The 165 was in the 335 tractor and the 220 was in the U302 and some military and industrial applications.
 
I've used my MM JetStar III for 33 years. It is a 1964 model. Very durable tractor in my opinion.
My torque amplifier slips in low range. And the disc brakes are not very effective.
The first thing I had to do was replace all the rusted tubes connecting the cylinder blocks and the heads.
They were just tin tubes to start with. The replacements were stainless steel and have worked well. It
was a job that required parts to be separated and put back together. I did it with a chain hoist under an
oak tree with a piece of plywood laying across the loader arms. I think the tubes and O-rings were less than
a dollar a set, but I worked pretty hard to replace them. Why didn't they feel the need to do it right the first time?
cvphoto89862.jpg
 
Also this same design was built in a V configuration for the UNI TRACTOR. The 206 is a very dependable engine and one of the best starting engines around.
MMDEL

This post was edited by MMDEL on 05/28/2021 at 04:21 pm.
 
Well, in a way they did it right.

Who would expect you to still want to use the tractor 50+ years later? It took over 40 years for them to give trouble.
 

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