K301/K321 questions

[bocephus1991]

I would go just what you need to clean it up if it's 20 over already and worn I would go 30. As for the k301 haven't heard of a 40 over piston, google it or go to stens website and see. I would have someone look and see if your k301 is a thick block or not.

[wj-ihc]

Got some more information tonight. Using a starrett inside mic with a 3-4 mic as a standard, my 0.020 301 measures under the minimun size for 0.030 in all spots, so it should be ok at 0.030. The current 0.030 is right at the high side of the new 0.030 spec and is within a thou top to bottom/side to side, so I will take it to the shop when I take the other block and new 0.030 piston and let the machinist decide if it will be ok. The 0.020 321 will be ok at 0.030. The second 321 was previously stuck but was standard bore. The largest spot was just under the min for 0.010, but with some light pitting it will probably need 0.020.

I also took some measurements of the outside diameter of the bore that protrudes into the crankcase on all four blocks. Both 301's were approximately 3.75. Both 321's were right at 3.9, so I now see what J-Mech was referring to. I will look into the 0.040 piston option for the 301. Below are some pictures showing the bore od.

[bocephus1991]

Did you use the dial caliper in the pic to measure your bore? If so it won't give a very accurate measurement . You need to measure where the piston rings run at they don't go all the way to the bottom or top.You really need a bore gauge to be accurate.

[wj-ihc]

Originally Posted by bocephus1991

Did you use the dial caliper in the pic to measure your bore? If so it won't give a very accurate measurement . You need to measure where the piston rings run at they don't go all the way to the bottom or top.You really need a bore gauge to be accurate.

No, the calipers were used to get a rough measurement of the od of the casting as shown in the pictures. I used a good set of inside micrometers to measure the bore, starting just below the carbon ridge at the top, taking two measurements at 90 degrees, then moving down to the center and bottom of ring travel. I used a 3-4 micrometer to verify the inside mic numbers from time to time. I actually ran a bore gauge down the bores to check for taper but didn't find anything that the inside mics didnt show.

[dbuck]

If you are interested, I have a brand new OEM still in the original box, Kohler piston +.030 for a K301, comes with wrist pin and retainers and a full set of rings. Part number 47-874-10-S. All items OEM Kohler.