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jebbear

K-181 Rebuild Issue

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Having decided to rebuild my K-181S engine as part of the restoration of my 856 Wheel Horse, just got the block back from the local machine shop. Something didn't quite seem exactly right (seemed a little loose) when I fitted the new connecting rod (.010 undersized) to my original crank which they were to grind for this new rod. Decided to verify their work with a piece of plastiguage and the result I got was approx. .004 clearance. If I am reading the manual right, this should only be .001 to .002 with a max wear limit of .0025. Looking for some advice from you seasoned veterans if I have an issue or am I misinterpreting something. I have not yet even re-contacted the machine shop concerning this hoping you guys can give me a little expert advice as to how to handle. Just a background, I took the parts to the shop initially for them to check what I needed. They told me to order a .010 undersize rod and a .020 oversize piston which I did from the bakt4kids guy on ebay. They then proceeded with the machine work. I saw another post on here where someone had issues with machine shops and just wondered how it was handled and if I have any options. As I stated, I did not speak to the shop yet and hopefully if I truly have an issue they will do the right thing. If I am off base and over analyzing, just tell me so and I will sleep a little better! Thanks.

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Take it to the shop and have them recheck it. Also make sure the rod cap is going on the correct way. Personally, if the shop did any grinding and boring I'd have them fit everything and after you assemble it I would have them inspect it. If there's a warranty issue later you'll have better luck if they signed off on how things looked before the engine is first fired.

 

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The shop I took my block & crank to wanted the rod before he did any grinding on the crank.

He was ok with boring the block for an oversized piston before I had the piston.

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2 hours ago, jebbear said:

told me to order a .010 undersize rod and a .020 oversize piston which I did

I am very surprised to hear they would do any machining without the replacement parts in hand. They know that there could be variation in parts from one source to another.

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Thanks for the replies. Just to clarify, I did have the parts ordered and at the machine shop before they did any work. I guess the way I typed that it sounded otherwise. Sorry.

Edited by jebbear
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48 minutes ago, jebbear said:

Just to clarify, I did have the parts  at the machine shop before they did any work.

Did they know what max clearance needed to be?  If so, sounds like they owe you a new crank.

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1 minute ago, Ed Kennell said:

Did they know what max clearance needed to be? ...

Ed, I would assume they did because the day I took everything in to be measured up to order, the guy pulled out the same Kohler manual that I found the max clearance in.

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From what you're saying,  as far as the measurements you got, they "over ground" the crank pin.

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24 minutes ago, oldredrider said:

From what you're saying,  as far as the measurements you got, they "over ground" the crank pin.

That is what my take is on all of this. I guess I'll be heading back to the machine shop as soon as possible to see what they have to say. Don't know what options I have other than another crank which I hope they take responsibility for. I did read something on Brian Miller's pulling site about being able to mill the mating surfaces on the rod to an "egg shape" hole, then reboring the rod hole to spec. for an overworn crank. Don't know if that is a viable option though. Any thoughts or opinions?

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Here is what I found out. I took everything back to the machine shop and had them re-check which I witnessed. Their bore gauge indicated .002 clearance rod to crankpin which is within spec but on the high end. The guy did say that plastiguage is really not that accurate for tight tolerances. I believe him now since I did my own experiment. I originally used the red (.002 to .006) and got a reading of .004 clearance. I now went and bought a piece of the green (.001 to .003) and got a reading of about .0025 which is the max clearance according to the manual. I have read many arguments concerning the accuracy of plastiguage and based on my own experiment I have to agree that it really is not that reliable. Anyway, thanks for all of the input and I guess I will proceed with the reassembly based on what I found.

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Interesting info on the plastiguage.

One caution on the use of manual measuring equipment for these small tolerances. 

Instrument  calibration, test blocks, rings, gauges, and pins are essential, and operator experience is critical.

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Ed, I totally agree. I guess I am at the mercy of the machine shop as far as calibration, etc. I was also rather shocked at the plastiguage experiment which indicated a major variation between the two different types because I always thought it could be trusted.

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Using plastigage has it's issues. Lets say you're checking a crank/ rod clearance on an engine you just tore down. You pull the rod cap and gee things look pretty good from the naked eye. You stick a piece of gauge on the crank,torque the cap and it shows in spec. Un beknownst to you the rod and crank are worn egg shaped. Always check a crank at multiple locations. 

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10 hours ago, squonk said:

Always check a crank at multiple locations.

I was always told to use four pieces of green  plastiguage at the same time. One on the rod, one on the cap and one diagonally on each side where the rod and cap meet. This way if any point is out of tolerance it will show up.

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