K161 Rebuild

[oliver2-44 11,184]

I have a K161 at a machine shop being bored and cylinder ground.

It will go in a 1961 red, or yellow tractor.

The engine was not from either one of the tractors and has correct crankshaft end length and engine pan mounting  bolt pattern for them (so spec number doesn't matter tractor wise).

 Early spec # K161's have a 2 7/8 2.875 design bore.  Later spec # K171 have a 2-15/16 2 2.938 design bore.

It has the early design bore 2-7/8)

Machine shop bought a 0.020 over K181 piston. So 2.9537. While they should have bought a "k181 standard bore 2-15/16 2.938

Since he bought a .020 over k181 piston he would have to take 0.083 out (0.0415 out per side) 

If he had bought a standard size K181 piston 2.9375 he would have had to take 0.0625 off ( 0.3125 of per side)

 

So I guess the question is can an early k161 be bored 0.083ths (0.020 over k181) or should I have them buy another piston that is standard k181 size and bore engine 0.063 over?

I have a K181 to be rebuilt  in the future, which is father down my priorities.  So not using the 0.020 over piston on this engine would not be a total loss.

Its at a good machine shop that rebuilds a lot of old things, (two gray hair 60+ guys and two 30 something guys. So I do trust them. 

It appears someone got messed up on the early and later k161 and didn't measure the actual bore before they ordered the piston. 

 

Now I just realized I need to check with them that they bought the right rod for it.

 

@Achto

@kpinnc

@ri702bill

@richmondred01

 

 

Edited 4 hours ago by oliver2-44

[squonk 45,268]

I'd have them put the right piston in and save the other for the other engine. 

[Achto 30,706]

1 hour ago, oliver2-44 said:

So I guess the question is can an early k161 be bored 0.083ths (0.020 over k181) 

 

To answer this question - yes it can with no issues. The later K161 & K181 are the same bore, just different strokes. But this only leaves one more rebuild for this engine .030 over. Personally I would have them order a Standard piston.

 

The K141 in my 633 is now a 7hp instead of a 6hp because of the cylinder size change and hard to get small bore parts.

 

1 hour ago, oliver2-44 said:

It appears someone got messed up on the early and later k161 and didn't measure the actual bore before they ordered the piston. 

 

Not good practice.  Mistakes happen I guess.

Edited 2 hours ago by Achto

[ri702bill 11,116]

1 hour ago, oliver2-44 said:

they should have bought a "k181 standard bore 2-15/16 2.938

Yes. As mentioned, this allows one more overbore - if caught in time...

Be careful with the undersizing of the crank journal. Sizing options are pretty limited to .010 under as I recall...

[rmaynard 16,834]

I had an early K161 (701) without ACR. I had it bored to fit a standard K181 piston, plus I changed the camshaft to a K181 with ACR. Easy start now with room to rebore several times.

[pfrederi 19,701]

Leaving enough for another overhaul....yeah  The engine got through 60 plus years.  overhaul should last nearly that long  (how hard are you going to work it??)