Wrist pin adjustment (Page 1/2)
Cunnive JUN 08, 01:47 PM



Piston, connecting rod, and wrist pin are all brand new.

As you can see, connecting rod griped the wrist pin before I could properly center it and now we have about a 1/4 inch off-center.

Would it be possible to adjust the wrist pin a little to properly center it?

Can I (or a machine shop) safely remove the wrist pin and try again?

Thank you!
Lou6t4gto JUN 08, 01:55 PM
absolutely
Notorio JUN 08, 05:37 PM
Are you pressing the pins in using sockets and a vice? Just curious how that is working. I guess you need some kind of Stop or line to indicate when you are centered ...
Patrick JUN 08, 05:51 PM

quote
Originally posted by Cunnive:

As you can see, connecting rod griped the wrist pin before I could properly center it and now we have about a 1/4 inch off-center.



Unless the design of wrist pins and connecting rods has changed a heckuva lot since I last rebuilt an engine, the connecting rod should glide freely over the wrist pin. Did you oil everything up prior to pressing the wrist pin in? Seems to me you had the connecting rod cocked off on a slight angle as you were trying to press the wrist pin through the piston. In my experience, the connecting rod needs to be wiggled back and forth while starting the wrist pin through it... to help avoid the "jam" you're now in.

Just push the pin back out and try it again.

[This message has been edited by Patrick (edited 06-08-2020).]

Cunnive JUN 08, 06:48 PM
I prelubed everything with assembly lube. I also had the wrist pin pre-inserted into the first bore on the Piston. That way once the connecting rod is ready, I place it into the Piston and then push it through.

As for the adjustment, I was planning on putting a long bolt through it with a large thick washer and nut on the other end. Then place a vice between them and crank it through with a ratchet.
Patrick JUN 08, 07:01 PM

quote
Originally posted by Cunnive:

That way once the connecting rod is ready, I place it into the Piston and then push it through.



Were you wiggling the connecting rod during this process... to make sure the pin was going through straight and that the rod continued to move freely on the pin?

Don't force the pin through if the connecting rod is "stuck" on the wrist pin. Push/tap the pin out until the rod is free to move again... and then start over.
Cunnive JUN 08, 07:19 PM

quote
Originally posted by Patrick:

Were you wiggling the connecting rod during this process... to make sure the pin was going through straight and that the rod continued to move freely on the pin?

Don't force the pin through if the connecting rod is "stuck" on the wrist pin. Push/tap the pin out until the rod is free to move again... and then start over.




I'm not sure I understand what you mean.

After I took the connecting rod off the flame and pushed the wrist pin through, there was a split second of adjustments as I was lining it but it eventually slid through smoothly until the connecting rod cooled and gripped the wrist pin securely.

That being said, I can freely (and smoothly) move the wrist pin with the connecting rod attached left/right/forward/back. All I need is to center it.

I hope that helps clarify!
pmbrunelle JUN 08, 07:26 PM

quote
Originally posted by Patrick:
Unless the design of wrist pins and connecting rods has changed a heckuva lot since I last rebuilt an engine, the connecting rod should glide freely over the wrist pin.



What you're describing is a floating wrist pin.

OP is talking about wrist pin that is press-fitted into the connecting rod (but free to rotate in the piston). I think that press-fit pins are pretty commonplace.

The shadetree mechanic method of assembling these is to freeze the pin to shrink it, heat up the connecting rod to expand it, and then quickly drop the pin into the hole. You have a number of seconds to get everything centered before the temperature differences subside and the connecting rod permanently grips onto the wrist pin.

With a hydraulic press, the pin can be pushed to the correct spot using the appropriate fixturing to support the piston (I don't know what this entails exactly). The local engine rebuilding shop should be able to handle the job.

[This message has been edited by pmbrunelle (edited 06-08-2020).]

Lou6t4gto JUN 08, 07:38 PM
ditto
Cunnive JUN 08, 08:42 PM

quote
Originally posted by pmbrunelle:

With a hydraulic press, the pin can be pushed to the correct spot using the appropriate fixturing to support the piston (I don't know what this entails exactly). The local engine rebuilding shop should be able to handle the job.




Ok so (with a press) moving the wrist pin over a little to center it won't be problematic or do I need to remove it entirely and redo the process again?