Open Modified Tecumseh Motorsports

racerx427

Member
Looking to make my Motorsports H50 into a open modified. The stock stroke is 2.500", I'm lookin to get a 2.702" piston to make 14.335 cubes. I know the crank journal will need to be ground down and piston cut, to exactly what I don't know. What Piston and Rod will work to make this?
 
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95 shaw

Premium User
The deck height is very close to that of a 5 hp flathead briggs. So piston and rod combo will be the same.
I built a 3 inch stroker into a 6hp tecumseh block. Used the same rod and piston family as the one I built in a briggs block. Cut the top of the piston for proper popup. Of course, I used commonly available briggs crankshaft and made a spacer shim to put tecumseh cam drive gear on.
 

HardRock

Member
I had good luck stroking the techumseh cranks, 2.6 - 2.7” stroke (since the journal was getting cut anyway to the Briggs size) and the using available pistons(for the Briggs)
The H50 stock bore is a .060 over compared to the Briggs IIRC

only issues with the H50 was breaking lifters, but that was before I found out there were billet lifters available.
 

95 shaw

Premium User
I would use the 4.425 rod and .640 ch piston with 2.5 inch stroke. You will need to cut piston for popup.

Calculations based on 5hp briggs using these numbers. You can confirm your deck height with careful use of a tape measure.


Your mileage may vary.
 
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