Kohler small block rebuild tutorial

[prondzy 3,881]

So yesterday I got a chance to build my k161. I got it back from the machine shop the cost to rebore the cylinder and regrind the valves/seats was $70. 

The first thing to a quality rebuild is and I cannot stress this enough, USE A CLEAN WORKSPACE!  I cleaned the top of my stand with brake clean,  anything to remove dirt and debris. If you don't have a metal top to use, try a clean peice of cardboard, something. You just spent money to do this right Don't skip on the clean work bench. 

Here is the most of my parts I am putting in. I am building this with an aftermarket ebay kit these are not kohler oem parts. I know there are always debates about this but I have built many  k series kohlers with great results if you think you need to add your  about this do it else where this is a how to thread.

You will notice in the background of the parts I have shown two things I like to use but in no way do you have to use them 

One is high tack Gasket sealant (helps hold the gaskets in place during assembly along with helping resist oil over time) and an assembly grease (you can use SAE 30 oil and still have great results). 

Here is a shot of the valve seats and cylinder walls, I have a great local machine shop and they do quality work.

First I install each piston ring (minus the wavy oil ring spacer) one at a time. I then use the new piston to push it into the cylinder and square it up to the bore.

I use one of the cutouts in the piston as a depth gage.

Using the chart in my kohler manual I look up the end gap spec for my motor and measure the gap with a feeler gage. I measure for the biggest and smallest accepted gap from the book in this case it was .007" to .017" so I find these two feeler gages and check I want the smallest to fit (then there is enough room for expansion when hot ) and I don't want the biggest to fit otherwise the piston will be sloppy (not to worry about because if your machine shop did a quality job you will be closer to the smaller number). You can find out specifically what each gap is but it is indifferent if you are between the specs.

 Next I lap the valves. Yes the machine shop did just clean up the surfaces to match but lapping creates a microscopic "fluff" ring that will allow the valve to fully seal against the seat.

Once again these two items only cost a couple dollars and can be bought at almost any automotive store. Get a small engine size lapping tool because one for doing chevy 350 valves won't be friendly because the suction cup will be too big. When it comes to the lapping compound there is water or oil based. Personally I prefer oil because it "sticks" to the surfaces better water just seems runny, just my opinion. I apply a small amount of compound to the valve face with my finger. Then suction the lapping tool to the top of the valve.

Place the tool in between your hands and roll it back and forth with light pressure and some rapid back and forth speed. This is a sound and feel thing for those who haven't done it before, at first it will grind like sand this is a good thing. As you roll the tool back and forth it will become quieter ( the compound has pushed out of the seat) I lift the lapping tool up which should pick up the valve a little set it back down and keep rolling in my hands. each valve should only that 30 sec to 1 min it is not a lengthy process.

Wipe out the seat and the valve with a clean rag (don't want that grit in the motor later) here is what the valve faces should look like.

Notice how each valve has a dull light gray ring on its face (this is the "fluff" we just created) notice how uniform it is all around the valve. This shows good contact between the valve and the seat.

Edited March 7, 2016 by prondzy
Grammar, spelling

[prondzy 3,881]

Now for assembly this is all explained in step by step in the manual. I might do things In a little different order but it's the way I do it, like measuring the ring end gap and lapping the valves they are out of the way and these parts are ready for later.  I also should mention i have washed all the reused parts 1 day before assembly, this is so they don't rust in the two weeks they sat in my garage waiting for the block. You can wash the parts off in a parts washer , i have even washed them down with brake cleaner and rags. I am using a home made engine stand, but for this part you might need to lay the block on its side

Install the pto side crankshaft bearing this will be a tight or snug fit you might want to put the bearing in the freezer for a few minutes before install. I just use a hammer and a brass drift to walk it in.

 

First install the govenor shaft that sticks out of the brass nut on the side of the engine. I lube up the end that sticks into the block and the tab that pushes against the govenor. Then I install the govenor gear itself, don't forget the shim that you hopefully wired to the govenor gear so you didn't lose it

Next slide the throttle govenor ring into the brass nut don't forget the choke cable holder. When you tighten the brass nut the throttle ring should spin freely if not you have something out of order or too much paint on something.

Install the screw that keeps the govenor from walking off the shaft, don't forget the small copper washer that sits under the Phillips head 

Lube up the valve tappet shafts and slide them into the block. Some motors can have different height tappets like an exhaust and intake . Then lube the faces of the tappets where the camshaft lobes will be riding. Lube the camshaft rod and slide it in from the flywheel side of the block, through the camshaft and the shim on the pto side that you remembered to wire to the cam. 

On the flywheel side tap the camshaft rod so it is indented past the surface of the block.

 

This was an earlier kohler so the timing marks are a little different than a newer k series small blck. There was a small dot on the camshaft gear that is now closest to the block I took a paint pen and marked the groove that the dot was located at by highlighting the teeth on each side of the groove. I then took my paint pen and marked the timing mark on the crankshaft.

When you install the crank these marks must line up otherwise you engine won't run or run well. It can be a little tricky to understand at first but you'll get it. This is what you want to see

Now that the crankshaft is installed properly, the bearing plate is next. Install the bearing into the plate if it isn't already stuck in it. It can be difficult to do this bearing plate shim part but I have found if you take two bolts 1/4-20 size and cut off the heads they make great alignment pins. 

The thick gray gasket always goes on first. Make sure you take your time to make sure the orientation is correct. The kohler manual says to add two to three of the other shims then measure.

I always add three if not put them all in right away either way it's your decision, in the end you just need to stay within specs .

I installed 3 and took a measurement and was within spec a little on the tighter side but still in spec, that is okay.

So once you have installed your shims put two of the bearing plate bolts in and torque to spec to compress the shims.

You then need to measure the gap betwwen the crankshaft and the crank bearings.

If the gap is split between both crank bearings you can give a GENTLE persuasion with a soft deadblow hammer to the crankshaft (careful on the threaded end and use caution) 

 I measured the maximum no fit, and the minimum it fit. So it is good to go.

Remove the two locating pins you made and install the other bearing plate bolts and tighten to spec. If you do not have enough space or too much you must add or remove the manilla shims accordingly . Then install the crankshaft seals you can buy special drivers for this or if you are comfortable and patient you can walk them in by gently tapping them with a small punch or brass drift. The key is to have them square in the bore when you are finished. The kohler manual tells you proper depth for the seals.

I will have to finish writing the rest of this tomorrow. 

 

 

Edited March 7, 2016 by prondzy
Grammar, spelling

[WHX?? 49,146]

Great thread Mike with excellent pics... I don't know how I missed it, mods this needs to go to someplace special for reference, I'll just shut up now so I don't ruin it!

[BOB ELLISON 2,981]

YES please continue with any and all rebuilds. I have a 1977 B80 I want to rebuild the engine and fix it up to cut grass

I got a lot of information from this. I want to start with the k181 8 hp and maybe try a k341 that I have extra for the c160.

there is no knowledge like old knowledge , Not saying your old but these old kohlers are not todays engines.

I would rather have a old kohlers then a new one any day . Thank you PRONDZY

   

[WNYPCRepair 1,921]

6 hours ago, WHX6 said:

Great thread Mike with excellent pics... I don't know how I missed it, mods this needs to go to someplace special for reference, I'll just shut up now so I don't ruin it!

Yeah, this should definitely be pinned

 

[prondzy 3,881]

Wow things have gotten busy here at home but I have managed to find some more time to finish writing this thread. 

Next install the rings on the piston starting with the wavy oil ring then the two thin oil rings one above and below the wavy ring. These rings are easier to put on the piston, you have to take your time and walk them into the groove. Once you have them installed offset the ring gaps of the oil rings. I place the wavy ring gap above the piston wrist pin hole, and one of the thin rings to the left and the other to the right about 1/2" from the wavy ring gap.

It is hard to see in this picture but I will show it in a later picrure. Now walk on the 2nd ring and the top ring. Use the diagram that comes with your piston for directional install of the rings.  Most all of the rings have some sort of notch in them like the one below.

 

Place the connecting rod in a vise wrapped in a towel, mark the orientation of the rod and cap with a marker.

After you have marked the cap remove it, and slide the wrist pin through the piston and the connecting rod and install the two clips that retain the wrist pin into the piston.

I measure valve lash next, small block kohlers use solid tappets so the valve lash must be set by grinding off material from the valve stems. I first check to see what lash I do have and then take the valve to the grinding wheel. When I have the gap close to spec I hand sand them in my tile with 600 grit sand paper.

 Then re check your lash with the camshaft lobe on the base circle of the cam this means that the tappet is in its lowest position. For those who don't feel comfortable doing this you can pay the machine shop to set this lash for you (they do have better grinders).

So here is a picture showing the orientation of the ring end gaps for reference the piston wrist pin holes are in the 12 and 6 o'clock potions in the picture. This spacing of the rings makes it that much harder for the oil to "blow by".

Heavily coat the cylinder wall connecting rod and crankshaft journal with clean SAE 30 oil. I usually use my fingers to apply it, then pour clean oil on the piston and the rings 

apply some oil to your ring compressor and squeeze the rings down on your piston 

You need to have the compressor tight enough to get the rings into the cylinder but loose enough for it to slide out of the compressor into the bore. Once again this style works just fine I have built enough engines that I have invested in a nicer ring compressor set.

Line up your piston in the bore, note the orientation of the mark you made with the rod and the cap this will need to line up in a little bit. The other crucial thing is the location of the hole in the rod cap. THE HOLE MUST FACE THE CAMSHAFT SIDE OF THE BLOCK! if you do not do this your rod will fail. This is because of the rotation of the crankshaft and oil lubricating the crank journal. I turn the crankshaft so the rod journal is at its lowest point so the connecting rod doesn't smack into it in the next step.

Using the handle of a deadblow or a wooden handled hammer make one firm and swift downward tap to put the piston into the block.  If you don't get it in the first time make sure everything is lubricated and in the right positionand try again. You want to get it in one tap otherwise you run the chance of breaking a ring.

Note the hole in the rod cap and it's relationship to the camshaft side of the block. Tighten the rod cap down to the spec in the kohler manual. There are two specs stated for some of the rods the first is a cap style which I used and looks like regular bolts holding the cap on, the other is posi-locked studs which the connecting rod has two studs sticking out of it and you 

 

The internals are pretty much done at this point. Install the valves you need your springs, valve keepers and retainer rings.

Feed the spring and retainer into the block spring first the push it up toward the valve guide and over the tappet. Slide your valve into the seat, and using your valve spring compressor, compress the valve spring and retainer together

When you have enough room, place the keepers on the stem. TIP: a small telescoping magnet, patience and a little axle grease goes a long way.

When you have both valves installed properly turn the crank over by hand, so each valve has opened once or twice, you now know that the engine turns, and if the keepers arent on all the way they usually have fallen off by now and you will know.

Install one of your breather gaskets (I apply gasket sealant on these gaskets) and then the breather plate and reed. NOTE the oil drain back hole is at the bottom. Place the rubber spacer, then the other gasket and the final cover with the nut, snug it down if you over tighten the nut you will bend the outer breather cover and oil will seep out.

 

Lube up the points rod and place it in the block hole. Add your points (most all kits come with new points)

Set the gap at .20" when the points rod is in the block the farthest it will go in during a hand rotation of the crankshaft.

Bolt on your points cover, don't forget your gasket, and grommet, this can wait till the engine is on the tractor and wired, but mine will sit in the shelf for a couple weeks.

Put on your head gasket, and head, torque to spec using a torque wrench, and install your spark plug. I personally do not use the spark plug that comes with the kit, I throw it out and buy a quality Champion spark plug,  in the case of a small block kohler a J8C.

Bolt on your engine tins and your almost done

 I still need to clean and rebuild the carb, after I do this tomorrow I will attach the govenor arm and set the governor.

 

Edited March 19, 2016 by prondzy
Grammar, spelling

[WHX?? 49,146]

On ‎3‎/‎19‎/‎2016 at 10:19 PM, prondzy said:

find some more time to finish writing this thread. 

Take your time Mike, we all know how time consuming doing a write up like this can be!

 

Couple of questions Mike, I notice you use some type of grease for an assembly lube, this is to protect during first start up I presume?

 

Also you don't paint until assembly is complete?

[prondzy 3,881]

WHX6, Yespecially the assembly lube is for startup this is a very critical point for all these new clean parts to be rubbing together. Clean motor oil can be used I just feel this light weight grease will stand up better at initial start up.

 

I would have painted the block and Tins before assembly after the machine shop but this motor went on the 702 I posted in Real Patina thread.

[grine_22 145]

Nice thread, enjoyed reading it. 

[JPWH 6,092]

Great detailed explanations.

Thank you for taking the time to post this build.

Now I think I can build my k181 for my 854.

[Coadster32 793]

Great threa, and thanks for taking the time to do this. Points set at .020...not .200  (typo I'm sure)

[Mike'sHorseBarn 3,014]

I suggest this thread be pinned to the top of the Engines section. I had a hard time finding it a second time lol

Edited February 23, 2018 by Mike'sHorseBarn

[Mike'sHorseBarn 3,014]

I'm an idiot. Found it in the reference section!

[stevasaurus 22,856]

@Mike'sHorseBarn   Welcome to the Reference Section Mike...this is something that @formariz and I spent some time fixing a couple of years ago.  Now that you found it, if you read any threads that you think should be pinned again...let me know.  This should be the 1st place to look for fantastic threads. 

[Mike'sHorseBarn 3,014]

Thanks Steve!

[The Gman 476]

[kwalshy 230]

First off, I love this thread.  Thank you for sharing your photos, explanation and more important....the time to post all of this.

 

I just got my Kohler K series 10hp block back from the machine shop after a bore over, valve seats recut and new valve guides installed.

I decided to read this post again before reassembly and after reading this thread again I thought about the valve tappets. 

 

The reason I ask is because I forgot to designate which tappet came from what valve during disassembly and now during reassembly I'm hesitant....

I measured the valve tappets with my micrometer and I have the following 2.768" and 2.756", so they are not the same length.

so which one goes where?  or doesn't it matter?

I don't want to move any further in my rebuild until I know what to do....yes I'm a first timer at a rebuild like this....shame on me for not keeping track with the tappet to valve relationship....

 

Any help here would be greatly appreciated.

 

Thank you

[oldredrider 2,549]

The 10hp tappets can go in either location as they are adjustable. Only on the small block (8hp and smaller) does it matter.

[kwalshy 230]

Thank you!

[ol~horses 4]

fascinating!

 

ol~horses

[LengerichKA88 1,883]

@prondzy Thank you for taking the time to do this, helps us “Redhorns” (don’t wanna cuss and say “G*€$N”) who are just starting out get an idea of what’s ahead. 

[Burnerman 758]

Great write up! Just 1 thing I think I missed was the valve adjustment. Do the valve ends get ground down on the smaller Kohlers to achieve proper valve lash?

[Pullstart 63,081]

@prondzy I was looking through this as a refresher...

 

have you ever done valve guides yourself?  It looks like Norman at isavetractors suggests a grade 8 bolt turned down to fit in the guide for driving it out and in... but I don’t know if this is a slide hammer job or a hydraulic press job?

[prondzy 3,881]

7 hours ago, pullstart said:

@prondzy I was looking through this as a refresher...

 

have you ever done valve guides yourself?  It looks like Norman at isavetractors suggests a grade 8 bolt turned down to fit in the guide for driving it out and in... but I don’t know if this is a slide hammer job or a hydraulic press job?

No Kev, if i need guides they are only a couple bucks each, installed/removed by the machine shop.

[Gregor 4,847]

This thread is invaluable to me. I read the whole thing. Some parts several times. My wife hollered dinner is ready a 1/2 hour ago. Oh well. I am in the process of rebuilding my K161 right now. There is some great info here. The only thing I didn't do was remove the cam. The lobes looked perfect, the weights for the ACR moved freely, and the governor looks good as far as I can tell. I am familiar enough with motors to understand the workings of the crank, rod, piston, valves and the like. Governors and ACR weights scare me a bit.  They just don't have them in Lawnboys and small block Chevys. After measuring everything, I decided not to bore the block or grind the crank. They seem to be fine. I have no particular plans for the motor at this time. When completed and running, it will probably go on a shelf and just be pretty. It won't have to work hard. Thank You so much for your effort.