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I've got a Simplicity 3212H that has a shattered rod.  This will be the 4th rebuild since 1973. This engine is the Briggs 300420 series single cylinder.  I'm considering a re-power.  I'm in the research phase. Does anyone here know what years and engines from other Simplicity or AC models will crossover and fit the engine compartment of the Simplicity 3212. I've currently got my eye on engines  that will fit a Simplicity 7112 or 7012. Does anyone know the engine compartment size of these two models? Also do you know  the original B&S model engine used in the 7112 and 7012?

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My 7112 six speed has a Kohler K301S.  When you say the size of the engine compartment, what measurements?  Bolt pattern, length, width? Any others?  I can slog out in the snow later to the barn and take some.

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First, welcome to the club.  

Any Briggs cast iron single cylinder with "rope start" will fit, including the 16HP ones.  The later ones with the ring gear starter might not fit into the older FDT frames like your 3212H.  It's a tight fit in the 7000 series frames and you need "square" tin over the bendix area to avoid interference.  Here's a pic of a 16HP Briggs with ring gear starter in my 7016H:


Some engines will require reversing the oil pan so the drain is on the correct side.  Obviously if you go with one with a ring gear starter, the S/G voltage regulator won't be needed and some re-rewiring is necessary (or some have kept the S/G).. Also if you install a Briggs, the ignition switch from your 3212H will be fine (magneto ignition).   

Also I  think any of the Kohler K series cast iron single cylinders will fit.  They have ring gear starters and battery ignition.  I think the starter is high enough to clear the frame.  Your 3212H ignition switch will have to be changed and some re-wiring is required (S/G voltage regulator issue).  

I'd do a Briggs replacement since IMO it would be easier.  But if you find a suitable Kohler, it would be fine.

Others should be along to express their thoughts.  


Edited by PhanDad
Added comments about Kohler starter clearing frame
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4 minutes ago, Jjsmachines said:

My 7112 six speed has a Kohler K301S.  When you say the size of the engine compartment, what measurements?  Bolt pattern, length, width? Any others?  I can slog out in the snow later to the barn and take some.

Great offer, but his 3212H has a FDT frame that's tighter than your 7100 series tractor.  A pic of my B-110 which has the same frame:



Note: the S/G is removed, but bracket still attached to block.


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I used a 16 HP Briggs flathead 326431 in my 65 Landlord 101 while I was rebuilding the 10 HP 243xxx. I used the oil sump off the 10 on the 16, and the brace from the top of the grille to the top of the engine did not fit properly. I think I had to leave the brace off, then replace it when I put the 10 HP back in. I would have left the 16 in the machine, but it was already bored to .030 oversize, with .009 wear in that bore. It is sitting in the floor right now, has been for a few years, waiting to see if I feel like spending the money to bore and sleeve back to standard.

The swap was bolt in simple with the change of the pan, only. It was changed to accommodate the oil filler at the bottom. The 16 HP would have had to be tapped for the filler like the 10 HP, since the 16 had a filler tube that interfered with the hood. I did not want to cut into the hood to make it work.

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5 hours ago, PhanDad said:

Any Briggs cast iron single cylinder

Includes the 240000 10HP series, the 300000 series 12 & 13HP and the 320000 series 14, 15 & 16HP engines. The 326437 has the flywheel ring gear starter & alternator but could be converted to a 326431 starter generator with your blower housing.

If  block is ok, there are three cylinder bore options. 1) There is a 0.010" oversize piston, P/N 299716, on eBay. 2)Sleeve the cylinder back to standard and use piston P/N 299688, two on eBay. 3)Members have successfully over-bored the cylinder for a standard 16HP piston, P/N 390364/792365.

Also, block with standard bore on eBay.

The 0.020" undersized connecting rod, P/N 390306 NLA, are hard to find. Probably have to use standard rod, P/N 299632, still available from B&S. If crank journal is bad, machine shop can weld and regrind journal. Or use new "Made in China" crankshaft, P/N 691797, on eBay.

Edited by Bill725
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Thanks for all of the good info. I'm looking at going with a 16 HP. My Current my 12hp is .020 under on the crank and my pistons are .030 over. I would also like to get away from the starter generator and go with a ring gear style starter. The little thing is a beast and nothing modern even comes close.   Therefore, I was looking into options to keep little red running. All of the info you guys gave me is enough info to help make a decision.

Edited by simp3212H
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