K181 piston in a k161?

[kpinnc 13,717]

I seem to recall some discussion of using a K181 piston on a K161 a while back but can't find it. Has this been done before?

 

I'm trying to decide the next course of action on my K161, as it needs some love on the bore. I'm not a huge fan of aftermarket internal Kohler engine parts. 

 

Mine has scratches that aren't deep enough to hang a nail, but they won't dissappear with a hone either. 

 

Anyway, if someone has done this before, let me know. I have a donor K181 that I can steal a piston from. Of course I'll get new rings. 

 

 

[ebinmaine 70,696]

@squonk or @Achto maybe?

[ri702bill 8,962]

What year K161?? 1961 & 62 blocks were small bore versions. 1963 & later the K161 has the same bore as the K181.

 

The difference between the two is the stroke - wrist pin locations may be different.....

Edited April 16 by ri702bill

[squonk 42,513]

Yes. Stroke differences. And if those marks won't clean up, I'd be skeptical that the rings would seal well. I Save Tractors sells decent aftermarket, piston, rings and gasket sets.

[oliver2-44 10,354]

1 hour ago, kpinnc said:

 Of course I'll get new rings. 

Have you measure the bore diameter for ovalness?

What does the crank pin look like and measure?

I recall @Achto has homed some quite a bit and put 0.010 over rings in.

It's not a perfect solution, but for a show cruiser it might be worth taking a little risk. 

I'll be in the wings watching closely as I have a k161 that needs some love for a project.

[953 nut 57,854]

This handy chart should help.

[Achto 28,761]

K161 and K181 share the exact same piston with a bore of 2.938". Stroke is longer on a K181 2.75" a K161 has a stroke of 2.50"

 

I just put a K161 / K181 piston in a K141 because the small bore K141 piston & rings are NLA. So I guess my 6hp is now a 7hp. No big deal.

 

I know you said that you don't like after market parts, but I have had very good luck with this seller. Measure your bore, decide how far over you need to go. Measure your crank, see if you need to go under size. Order your appropriate parts, take them to your machinist, have them size every thing to the appropriate clearance. Have an engine that last for years.

https://www.ebay.com/itm/383629419791?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=383629419791&targetid=2299003535955&device=c&mktype=pla&googleloc=9019452&poi=&campaignid=21214315381&mkgroupid=161363866036&rlsatarget=aud-1412318123216:pla-2299003535955&abcId=9407526&merchantid=6413034&gad_source=1&gbraid=0AAAAAD_QDh_FiL253wnc17lC2HGXdbKJN&gclid=Cj0KCQjwqv2_BhC0ARIsAFb5Ac9Saqnw7Jo2IKHOE-MoiymNVUKf7sQfl7cuyFwbSAzv4ot2bbgs-pwaAqhoEALw_wcB  

 

Kohler manual.

https://resources.kohler.com/power/kohler/enginesUS/pdf/tp_2379.pdf

 

Page 1.6 has all the specs for the K model engines.

 

[kpinnc 13,717]

4 hours ago, ri702bill said:

What year K161??

 

Supposed to be 1961. This is on my 701. 

[kpinnc 13,717]

4 hours ago, ri702bill said:

What year K161?? 1961 & 62 blocks were small bore versions. 1963 & later the K161 has the same bore as the K181.

 

So theoretically my 1961 K161 should have .063 to play with on the bore if I used a standard K181 piston?

 

I verified mine does have the smaller bore. First mic checks were between 2.875 and 2.876. 

 

At least that's what the chart below says since later K161 and K181 had the same 2.938 bore... The stroke was the same on both versions of the K161. 

 

Of course this is all preliminary. I haven't looked at anything beyond the bore. 

 

@Achto Thanks for the link. I will definitely check the seller out. 

 

[ri702bill 8,962]

Yup, early small bore. The good news is that it can indeed be bored to the larger size for a perfect piston fit - if you are willing to throw some good money at it....

[WHX?? 50,698]

15 hours ago, kpinnc said:

I'm not a huge fan of aftermarket internal Kohler engine parts. 

Why is that KP? 

We've always had pretty good luck with them. Kohler parts just too $$ but I suppose if she's special. 

6 hours ago, ri702bill said:

throw some good money at it....

Not necessarily Bill... aftermarket parts and Dan has a shop that is real reasonable and great work. 

 

14 hours ago, Achto said:

small bore K141 piston & rings are NLA.

I have found them but real dicey in oversize. Just punch it out to 181 over specs. 

701 is just a trailer queen tub/puller you may be able to just do new rings. Measure and see how far out specs are. 

[Fordiesel69 267]

I will add, you can use aftermarket parts no problem if you machine the engine to the parts.  Do not machine the engine to the specs in the book and expect the china parts to work.  They simply wont. 

 

I lost all my local machine shops so im really in a bind for the future.  Im selling all my stuff that is due for machine work and keeping the virgins or stuff that has already been refreshed.  

[kpinnc 13,717]

1 hour ago, WHX?? said:

Why is that KP? 

 

Well at this point it's just guesswork. I hope to disassemble the engine over the weekend and see what is what. So long as the bore is all that needs attention? It's golden. 

 

The donor K181 came from a very old generator and has a 1 inch long, partially tapered crankshaft. The engine is unsuitable for any normal application on a Wheel Horse. I'll need to take it apart as well and verify the parts I need are in spec. If not, I'll have no choice but to go aftermarket. 

 

There is a local engine shop that I've used before as well. They do exceptional work and in the past at least the prices were good. I just take the block (valve train intact) and they bore and hone the cylinder to spec and grind the valves and seats. Makes for a plug and play reassembly.

 

Of course I'm at the beginning of this. What I find inside the K161 will determine what I do. 

Edited April 17 by kpinnc

[kpinnc 13,717]

Oh boy what a mess this has become in short order...

 

I'm not sure what the "early/ late" year was for sure, but my engine was not an early version as I previously thought. ***teachable moment*** I know better than to use calipers for precise work, but given there is a .060 difference between early bores and everything after, I figured they would be close enough to see the difference. I was wrong. My engine does have the larger STD bore but has the K161 rod and crankshaft. That tells me this engine was replaced entirely or partially if the large bore came out around 1962.  Unfortunately the crank pin mic'ed out .012 under the max wear at the engine shop this morning. My donor engine that has K181 stamped on the tins is actually also a K161 because of the same bore and (same part number) longer rod. Pics of both below. Sorry but neither was cleaned up yet. 

 

My block will be bored as well as the valves and seats ground sometime in the next week or so per the shop. I don't have a piston to start with because we're not sure yet how much it will take to get the grooves out. Hopefully .010 but possibly .020. I have until then to decide what to do so about the crank and rod options.

 

Honestly it makes sense to me to replace the crank with one from a K181 (or M8) that is in spec and go with a K181 (0.250 shorter) rod. Otherwise I'd have to grind the original crank pin to .020 under and find a decent aftermarket undersized K161 rod. 

 

I can't use the donor crank because it has a 1 inch long tapered output shaft. 

 

So- the original question about K181 pistons being used in a K161 seems to be answered. Mine already had the same size (2.938) bore in it. 

 

 

 

 

Edited 3 hours ago by kpinnc