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Engine block question

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I want to repower a Simplicity 3310V with a Harbor Freight 420 13 HP motor.  Originally the 3310 came with Briggs model 243431 10 HP cast iron engine.  I also have a 3112H which came with the Briggs model 300421 12 HP.  I have the 300421 but the 3310 came with no motor. 

I thought I heard that all of these early engine blocks were the same.  I need to know how much to raise the Predator engine to align with the 3310 drive shaft so here is the question:  Is the distance from the bottom of the block to the middle of the crank shaft on the Briggs 243431 the same as on the Briggs 300421?

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Grandpa was a carpenter and he always told me, "Measure twice, cut once."  So I measured again, more carefully this time, and came up with 15/16.  Don't want to over work that fiberglass disk.

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50 minutes ago, BLT said:

The Briggs centerline dimension bottom of pan to C/S center is 6.139 + or - .012 inches.

So the tolerable range is between 6.127 to 6.151.  I measured 6.5" to the top of the crank (Briggs 300421) at the flywheel end.  The crank stub is 3/4".  Half of 3/4 is .375 so 6.5 minus .375 is 6.125.  I'm low by .002".  I did the same thing with the Predator motor  and came up with a difference of 7/8" (first measure) and 15/16" (second measure).  In light of my under specification outcome, the second measure of 15/16" is probably justified.

Now the question is, how much variation will that fiber glass coupler stand?

Edited by wwbragg

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