I am not pleased and I was hoping for some common advice.

Stock rebuild, all the parts are clean.
The wrist pins are really tough to put into the pistons.
I put the pins back in the cleaner to see if maybe they had some coating on them....nope.

How tight are you guys tolerant of wrist pins?
Do you expect to use a brass drift, or are you only happy when you can push them in with your hands only?

They do fit in the rods with no hammer, but the pistons are the problem.

Rich

I suggest heating the pistons like we used to do with 356s. The Cap'n

I know I can do the heat/freeze thing.
I am planning to assemble/disassemble this at least once and I was hoping to not have to use a hammer.

Just seemed a bit tight...I will try a heat gun to see...they are close.
Rich

..........well r-towle.....seems like the piston wrist pin bore is a little tight,on the pistons you have. I have found (over many years) that the ideal pin fit is one that is a push in fit by hand., without any forcing.-just slides right in-and with engine lubricant on the pin (20/w/50) it,s just a little stiffer/tighter-but still is a push fit...typically this tolerance is so close you just about cannot measure it with normal indicators/calapers/etc.-were talking .0005 ths -1/2 thousands.-It,s still a push fit.....Here,s how to get it...1) take an old wrist pin-see how it fits-should be the same-tight-.2) clean the OLD wrist pin with crocus cloth, you'er actually sanding it down.-you might get .00025ths off if you stay after it., 3) get a l-o-n-g- bolt, cut off the head, insert thru wrist pin-use nut to secure-rubber grommit/hose /etc next to DRILL motor side...4) now you have a wrist pin honing tool....5)..with a grinder taper cut JUST the end of the pin a very-VERY little bit...just enough to get the pin inserted into the piston bore....6)..Now with drill running you can feel the old pin hone the piston., use lots of W-D-40..to keep the honing pin /and piston lubricated., you can see the color change to aluminun.-ish liquid as honing is in progress.7) do a couple of COMPLETE strokes thru the piston., 8) clean piston w/p bore with brake cleen,..try inserting a /one of the new pins. if it,s NOT a push fit...go back to honing a little more.9) in no time at all you will get the "feel "..of a perfect bore for the new wrist pin.10) you will note that the connecting rod pin bushings ARE NOT/involved in this process.........Murray

Before you do all this, what is the temp where the parts are stored? If it's cold where you live, let them soak up to about 80 deg. The pins won't shrink enough to measure in the cold, but the pistons will. .0002 change on aluminum is very easy to see from thermal change. Thats the difference between interference fit and press fit.

...............very good idea....temperature should be NORMAL room temperature.(whatever that is)...80 degrees sounds good to me.....

These are the original pistons and pins...sitting in a very cold barn.
I will bring them inside to see how that works out.

Rich

Yeah, get them equalized to room temp. They should slide in.


My experience sanding bits has been on hardened crank/cam journals/lobes.

You can hit those with 600-2000 all day, and take nothing measurable off in the motors I have dealt with.

I verified with a Starrett micrometer good to .00005 multiple times in multiple points all over.