new beginnings for 2016 – project 81 · ©2016 by zack peterson and podium finish, llc – 9...

©2016 by Zack Peterson and Podium Finish, LLC – www.antiquetractorpullguide.com 1

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The final pull of the year proved the Massey Harris 101 Senior had potential to run with other 6 & 8mph tractors. With some minor details on the 101 to attend to as the 2016 season kicks off, a new idea soon formed. In the past several years there has been a trend in pulling toward lighter tractors. The 101 Senior is set up to run 4000-5000# classes, and some pulls in the area have classes as light as 2500#. The new idea is something others have done – build a little brother to your power house tractor. Some Podium Newsletter readers may recall the Massey Harris Mustang project that was completed several years ago. The Mustang was the final incarnation of the small chassis Massey Harris tractors. The first versions was the model 81 built between 1941-1946, the second was the model 20 from ’46-’48 and the third was the model 22 from ’48-’53. The Mustang was built from 1953-1956 and was most similar to the 22 with the F140 Continental four cylinder flathead engine. The 22 and Mustang had the later flat bar style front grille similar to the 33 and 44 tractors. The 81 and 20 had the triangular shaped bar grille like the earlier 101 Junior and 101 Senior tractors. Thus, for a light weight pulling tractor, the model 81 would be the ideal little brother to the 101 Senior of the same era. With regards to the Mustang, it would be built much differently now than it was 5 years ago with the advances in lightweight hubs, wheels and engine builds. In fact, at the time the tractor was only really suited for a 3000# class since it was too heavy for 2500# and way outclassed at 3500#. Still a fun tractor to drive and pull, it was a tough decision to sell it in 2012 to help fund the B427 powered Massey 101 Senior build. There are some regrets about that sale, however the great Gary Baker once told me, “Don’t worry about selling a tractor, there are lots more out there and you can just build another one…better.” With that in mind, the possible 81 build started to intrigue.

New Beginnings for 2016 – Project 81


Project 81 (cont)

One of the problems with the Mustang is that it was relatively heavy in comparison to other makes – the Allis CA, Fords, and Case VAC notably. The 2500# class is currently ruled by little AC’s, which have skyrocketed in popularity since the D14 and D15 engine can be retrofitted so easily. Shoot, even I jumped on that bandwagon with the D12 and was ready to roll until an engine knock sidelined that project. It may be revisited, but opportunities elsewhere presented themselves in the latter part of 2015 that were too exciting to ignore.The first interesting thing that happened is that I have a friend who pulled a Massey 22 in another state. I had helped him with parts and advice to fit a B427 Continental engine into a 44. So excited about the B427, he decided he would concentrate on that build and park the 22 since it had developed a funny noise. Upon further inspection, one of the buttons that retained a piston pin had come loose and scored the cylinder wall. The engine would have to come apart, be rebored and put back together. Since he had lost interest in the tractor, he offered the engine to me. The good news is….drum roll….it’s a stroker engine. It is an F162 engine from a model 30 (same block) that has been bored and stroked to 205 cubic inches.

1946 model 81

The next step was to locate a tractor to put it in. After keeping an eye out, an 81 came up for sale not far away. In a partial trade for a large Conoco sign, the Massey Harris 81 was brought home. It’s a perfect candidate to build into a puller – a lousy repaint with a goofy parade seat that runs and drives.


Project 81 (cont)

Here is one good thing about using an 81 tractor instead of a 22 or Mustang for a light class – the 81 was built lighter. Yes, it has the same engine, frame and transmission, however the axle housings, brake assemblies and front pedestal are all built lighter duty. The factory weight is about 250# lighter than a 22. In starting with a lighter tractor to begin with, I soon realized the potential of a 2500# beast could easily be a reality. Furthermore, these tractors were also built in a standard tread version with short axle housings. Some may recall this trick on the Massey 101 Senior –standard axle housings with custom hubs to lose some serious weight. In thinking about this, I began to keep an eye out and ran across a Massey Harris 20 standard that is a parts tractor.

MH 20 standard

To verify the beginning weight, the 81 was taken to the scale. It weighed just over 2500# the way it sat, with fenders, platform extensions, pto, and funky home built seat assembly. Also, the split was 800# on the front axle, which means about 32% of the weight was up front. This is light for the front end and the tractor will need a diet in order to pull properly.


Project 81 (cont)

So to quickly summarize, this is the basic formula for this build:

Stroker engine (205 cubes)Stock gearingShort axle housingsCustom 9 bolt hubs (CAP Bros Motorsports)Custom 38” wheels (CAP Bros Motorsports)Either 12.4-38 or 13.6-38 tires depending on weight

MH 81 rear showing the platform & seat

And with a clear game plan, the disassembly work began. First the seat assembly, platform, fenders were removed, which collectively weigh about 150#. Next, the tractor was disassembled down to the major components. The 20 parts tractor had the axle housing removed and swapped for the long 81 row crop axles.

Standard axle on the left, row crop on the right.


Project 81 (cont)

This view shows the comparison between standard and row crop axle housings.

Mock up of the short 20 standard axle housing on the 81 rear end.


Project 81 (cont)

The 81 WheelsAs with the other Massey Harris pulling tractors in the stable, the 81 will get the CAP Bros Motorsports rim centers. This time it will be taken a step further though, where Pete Petznick is now able to build an entire lightweight rim assembly. He calls it the “ultra light” rim, where a light gauge band is welded into the center of the rim to remove weight, and then his 5 spoke rim center is added to form the whole assembly. The result is a lightweight rim that is somewhere between aluminum and traditional stock rims. For the 81 running a 2500# and 3000# class, a 12x38 rim is all that is required for 12.4-38 or 13.6-38 tires. That being said, a stock 12x38 flat based rim without a center weighs around 90#. That means welding in a CAP Bros 24# wheel center would make it a 114# assembly. In using lighter gauge metal in the rim assembly, the completed ultra light rim assembly with the center in it weighs an astonishing 75# each. This saves almost 80# total in rim weight for a tractor where every pound is critical.

CAP Bros Motorsports ultra

light weight 12x38 rim assembly. Notice weld beads

for flat base where lighter

gauge material has been added. To find out more,

contact Pete Petznick at www.capbrosmotorsports.com

or 816-308-8879


Project 81 (cont)

The 81 Axles & HubsThe standard tread axles that will be used in this build are a smaller version of the same design used on the 101 Senior. They are tapered with a keyway and a retaining nut. To build a set of hubs, Pete at CAP Bros Motorsports was again the contact. Pete can make hubs of any design and for this tractor we may try something completely new – a tube axle with 9 bolt hub plate. Stay tuned…

MH 20 standard tread tapered axle with keyway

CAP Bros Motorsports tube axles with 9 bolt hubs


Project 81 (cont)

The quick & dirtySince this is a pulling tractor and not a concourse restoration, this project will get a fast track to looking good similar to the 101 Senior. Except for the rear end and engine, all other parts will go to powder coating to make them look good. Now that the transmission and axle housings are clean, the next step is metal fabrication for the hitch, wheelie bars and weight brackets. All components are to be properly fitted before being sent out for powder coating.

Cleaned transmission case and axle housing. The next

step is fabrication.


Monster MM UB

This year marks the 3rd anniversary of the Minneapolis Moline UB blowing out a frost plug at the Father’s Day pull. The tractor has been sidelined since then and recently my we have gotten more serious about building an engine for it. The tractor currently has a high compression 403 engine in it that has good power. In fact, the engine still runs and sounds great, it’s just the frost plug between the cylinder heads that needs to be fixed. Unfortunately, one cylinder head has to be removed to repair it. After seeing the success of a big build MM U at pulls like Tunica and even in our area, the research began to piece together a monster to compete in the fast classes. The build will use the basic components shown below.

Crankcase – MM M670Crankshaft – MM G (6”), stroked to 7.5”Cylinder jugs – HD800 (5.312”) bored to 5.5”Connecting rods – billet, 12” c-cCylinder Heads – 10A4229

For those not familiar with the HD800 engine, it was a large six cylinder irrigation pump engine. In doing the math, it makes this 4 cylinder beast 713 cubic inches. Recently, we began to round up the parts for this build.

HD800 irrigation pump engine. 5-5/16” bore x 6” stroke, 250hp

MM UB ready for an upgrade


Monster MM UB

Below are pictures of some of these Minneapolis Moline components. The interesting fact about MM is they cast cylinders in pairs that were similar on four and six cylinder engines. Although the HD800 blocks need a bit of machining to fit properly on the 336 crankcase from the M670 tractor, the fact that these can be pieced together to make big cubic inches is pretty neat. More details on this build will be shown in the coming months.

HD800 cylinder block. Notice the bore size compared to the Pepsi can.

The 10A4229 cylinder head. These were used on later engines and are easily identified by the square ports. Early heads had round ports.

Crankcase from an M670

tractor, originally a 336 cubic in engine.


Coming up…

• Tire Cutting

• Learning The Hard Way

• Quincy Tractor Pull

• And more…

I want to hear from you! If you have

feedback, requests or information you

would like featured, please send an email to:

[email protected].

Next Newsletter available soon!

MH 101 Senior at Quincy, WA

new beginnings for 2016 – project 81 · ©2016 by zack peterson and podium finish, llc – 9...

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