Wrist pins won’t fit in new pistons

[jkmdg84]

I am working on rebuilding the engine on my B. Got past my clutch throw out bearing struggles, but now I ran into another snag. I was starting to install new piston and new wrist pin on my first rod, but I discovered that the new wrist pin will not go through the new piston at all. It will barely get started and won’t move with thumb pressure. The new wrist pin fits in the rod bushing just fine. Is this a common issue, or do I new to talk to my retailer? Should I have to add heat, cold, or oil to the piston or wrist pin to make it work? It’s a Red Power brand piston kit.

 

[gidtex]

U need to put oil on bottom parts.

 

[rustred]

In short , It’s a machine shop job.

 

[fixerupper]

They should be full floating. Some car engine pistons need to be heated to install the wrist pin but not your farmall unless something in piston design has changed.

 

[David G]

Some are press and some are full floating.

 

[rustred]

i said what i said because he said the pin fits the rod bushing, but that dont mean its good either. the bushing is most likely worn out and
they should be replaced and fitted in a machine shop.but anyhow you need to heat the pistons to 200 degree's and the pin should slide in

 

[used red MN]

Do you have very much experience with assembling engines? It kind of sounds like you don’t. Oil probably will not help your situation although for final assembly it is a good idea for any moving parts that have an assembly clearance spec to have a abundant oiling like almost dripping. In your situation I would apply a small squirt of your favorite penetrating oil in the piston pin bores. Then attempt to install the pin without the rod with force equal to what you mentioned. When it stops pull it back out. Now look in the piston pin bores the spots that are shinny are the high spots that are not letting the pin slip in. I wonder if there is just some minor machining distortion at the snap ring grooves. If you decide to use my following suggestion I would first alert the supplier of what you found and tell them if this simple process does not fix the issue you will contact them for further instructions. If it were me and I saw some ridges by the snap ring grooves I would take a brake cylinder hone use some engine oil and give it a quick 3 to 5 second hone in the pin hole. Clean the pin hole with clean solvent then try the pin fit again. If this does not seem to easily allow the pin to fit in one of the pistons I would stop. Contact the supplier to either replace the parts or agree to pay you to take them to a machine shop to have them properly fit.

 

[pete 23]

Put the piston in a bucket of hot water. Used to do that a lot on IH engines. If it goes in alright after a couple minutes in hot water they are fine. If not, well.

When I didn't have hot water available I would put a little gasoline in the piston from the bottom and light it up.

Aluminum pistons dry right off so no worry about the water. Blow it off, oil the hole and push them in. Make sure the rod bushing do not have any play with pin installed.

 

[wore out]

(quoted from post at 17:03:48 01/11/21) I am working on rebuilding the engine on my B. Got past my clutch throw out bearing struggles, but now I ran into another snag. I was starting to install new piston and new wrist pin on my first rod, but I discovered that the new wrist pin will not go through the new piston at all. It will barely get started and won t move with thumb pressure. The new wrist pin fits in the rod bushing just fine. Is this a common issue, or do I new to talk to my retailer? Should I have to add heat, cold, or oil to the piston or wrist pin to make it work? It s a Red Power brand piston kit.

Did the piston and wrist pins come packed together as a matched set? (hopefully)

As the other poster says, the aluminum pistons needed to be warmed to a controlled temperature, then the pins will literally "fall" in to place. DO NOT hone or otherwise try to enlarge the bores in the piston!

But if you want this to be a quality repair and not a "hack job" you need to pack up the pistons, rods, and pins and take them to an automotive machine shop and have the rods checked for straightness and the "big end" checked for bore size and "out of round", then have the bushings checked (and likely replaced) then "fitted" to the individual wrist pins.

 

[pete 23]

Well, can't argue with that. But those old engines aren't real fussy within
reason.

 

[Janicholson]

.0005" will live .002 will knock. The worst part of a free floating pin is bad keepers. the piston will be in the above 230F range at the pin. Jim

 

[Ken Hansen]

In over 40 years as a heavy equipment mechanic worked on dozens of engine where you had to warm pistons up to let the wrist pins slide into place. Remember that the rate of expansion for aluminum is much faster than for the steel of the wrist pin. So after a few seconds of running the pins will be nice and free in the piston.

 

[jkmdg84]

Thank you for all the replies! I will try heating a piston and see what results I get.

 

[Dave41A]

You're advocating a press-fit method which may or may not be the appropriate method in this situation. There are many different styles of wrist pins and different styles of installing wrist pin locks, which vary by manufacturer. The link I provide below shows 6 or 7 different ways of installing different manufacturer's pins. Snap rings, spiro-locks, wire locks, press-fit, Circlips, pin buttons, etc. If I looked further I would probably find more. Even for press-fit, sometimes the pin presses into the connecting rod, and sometimes into the piston. And this is all assuming the piston supplier provided the proper pins in the first place, and not an oversize set.

If the manufacturer didn't specify what type of installation method to use, then the proper thing to do would be to ask if others had some experience with the same brand. A truly experienced mechanic will STOP and ASK if things are even slightly different from the previous 50, 500 or 5000 engine rebuilds.
SOME of the different types of wrist pin installations

 

[miangus]

I have never seen a kit or set of pistons where the pin did not come in the piston, so you know it fits. As noted, at least carefully inspect the pin to rod bushing clearance. The pin when installed in only the rod should not tilt. I usually install new rod bushings and have them fitted at a shop. No fun to start a rebuilt engine and have a slight knock.

 

[Jim Becker]

The original design and specs for that engine say the piston pins are full floating. The pin clearance in the piston is 0.0005 (half of one thousandths) and in the rod 0.0007. They should be a "hand press fit". I suppose it depends on how strong one's thumbs are, but it seems to me the OP's "move with thumb pressure" should be good.

Replacement parts should fit the same way unless there is some reason for a change. The original pistons were grey iron. Use of aluminum replacements may be one reason. The OP said nothing about his new pistons being aluminum.

If the supplier of the replacement pistons has any other standard or procedure for fitment, they should supply that information with the pistons. In the absence of such, they should be contacted for an explanation or replacement parts as appropriate.

 

[pete 23]

In over 60 years of working on IH engines in dealer and self employed, I put
in one set of cast iron pistons. They were some the dealer had laying on the
shelf and he talked a customer into them at a low price to get rid of them.

A few engines I tore down for repair had original cast iron pistons but most
had aluminum as they had already been over hauled and I started back in
1958.

The M Diesel came with aluminum pistons from factory.

Original so called power improvement packages for a Farmall M and H was
aluminum pistons but still standard bore, thick sleeves. That was in about
51.

 

[wore out]

(quoted from post at 14:00:34 01/12/21) The original design and specs for that engine say the piston pins are full floating. The pin clearance in the piston is 0.0005 (half of one thousandths) and in the rod 0.0007. They should be a "hand press fit". I suppose it depends on how strong one's thumbs are, but it seems to me the OP's "move with thumb pressure" should be good.

Replacement parts should fit the same way unless there is some reason for a change. The original pistons were grey iron. Use of aluminum replacements may be one reason. The OP said nothing about his new pistons being aluminum.

If the supplier of the replacement pistons has any other standard or procedure for fitment, they should supply that information with the pistons. In the absence of such, they should be contacted for an explanation or replacement parts as appropriate.

In all my years of hanging around here that has to be the most CLUELESS post yet!

 

[rustred]

just listen to Pete 23,... you will not get any better info than from the man with hands on experience. and... if you find a unit with cast pistons you hit the jackpot.