Piston Pin Bushes

[jkdmag]

Interested in the opinion of others as to the practically, and suitable materials, for the manufacture of bushes to be inserted into a piston pin boss to allow use of a smaller piston pin. Hoping to adapt a piston with 16mm pin to a crankshaft with 14mm pins. Initially thought bronze to be a suitable material, but is steel an option.

 

[Tmoose]

Some trucks used to have bushed pistons. Maybe they still do.

Looks like VW deezuls did as recently as 2004. Looks bronze-y, but there are dozens of flavors of bronze.

https://dyw03owr7vs3n.cloudfront.ne...129267/product/open-uri20140226-13157-y63hif.

I think some efforts to bush high performance Corvair car pistons didn't work out well. I believe differences in thermal expansion and heat transfer from piston to bushing were suspected as issues.

http://www.speedtalk.com/forum/viewtopic.php?p=89560

Have you investigated modifying the con rod for the larger pin? That gives you the option of equalizing the rod length, and creating a straight rod without resorting to bending the conrod to correct misalignment.

 

[jkdmag]

A follow on question, for full floating piston pins, what is the relative movement/lubrication conditions between the piston pin boss, the pin and the small end bearing. From observation the existence of an oil hole in the small end bearing and none in the piston pin boss holes suggests that the pin moves in the small end and simply rests in the piston boss.

 

[SwinnyGG]

the pin moves in the small end and simply rests in the piston boss.

Correct.

 

[Tmoose]

I'd look at more pistons.

Some have quite elaborate measures to feed some oil to the wrist pin bores.

http://www.racetep.com/media/wysiwyg/others/jeoptions.jpg

http://www.us.mahle.com/media/motorsports/features-and-benefits/pin-20bore-20f_b_text_image.jpg

http://www.us.mahle.com/mahle_north...ces/motorsports-and-special-engines/formula1/

http://www.mooregoodink.com/news/wp-content/uploads/2014/09/WisecoCutaway-300x239.jpg

Also, pictures of uses wristpins often show pretty significant surface changes in all regions. Wear and heat discoloration.

http://www.928sg.com/images/wrist-pins.jpg