Topic: RC 67mm Venolia Pistons

[mick7504]

Can anyone throw some light on the rubberised inserts and the reason for them?
The pistons have a built in taper of .035" and the inserts measure just a whisker over the skirt base diameter.
Mick

[Sam Green Racing]

They are teflon buttons mick, can't come out like a circlip.

Sam.

[bwaller]

Some early thinking I suppose, but I can't help.

I'm curious if there is any means to attempt oiling the pin in the boss? No holes in the underside.

[Steel Dragon Performance]

They were used to reduce piston skirt drag on racing pistons. Life was not long on them, engine would be rebuilt after so many races.

[Sam Green Racing]

Well spotted Brent, I didn't even notice that the buttons were in the skirt and not in the pin hole.

They are still probably teflon buttons though, to reduce heat in the skirt.

Sam.

[Steel Dragon Performance]

yes they were teflon buttons. I have seen them in dirt bike pistons to.

[MRieck]

 That's a lot of piston for a 15mm pin Mick.   They have been balanced as a set and, of course, have the vertical gas ports.

[Big Jay]

That's a lot of piston for a 15mm pin Mick.   They have been balanced as a set and, of course, have the vertical gas ports.

Unless you have a pin that will handle that and more; http://aperaceparts.com/wristpins.html


In top fuel motors, the skirts were undersize and the buttons installed, then turned in a lathe. This way the piston could never contact the sleeve.

[MRieck]

That's a lot of piston for a 15mm pin Mick.   They have been balanced as a set and, of course, have the vertical gas ports.

Unless you have a pin that will handle that and more; http://aperaceparts.com/wristpins.html


In top fuel motors, the skirts were undersize and the buttons installed, then turned in a lathe. This way the piston could never contact the sleeve.

When did you start making 15mm pins Jay.......I haven't seen them in your catalogs for years and years.

[kos]

They are teflon buttons mick, can't come out like a circlip.

Sam.

Sam, Look again, those are in the thrust surfaces of the piston, like drag racers do. Not anything to do with wrist pins.
KOS

[kos]

That's a lot of piston for a 15mm pin Mick.   They have been balanced as a set and, of course, have the vertical gas ports.

Unless you have a pin that will handle that and more; http://aperaceparts.com/wristpins.html


In top fuel motors, the skirts were undersize and the buttons installed, then turned in a lathe. This way the piston could never contact the sleeve.

When did you start making 15mm pins Jay.......I haven't seen them in your catalogs for years and years.

Thanks Mike for pointing this out and for Jay for making them!  Great news for us engine builders...

KOS
M3Racing USA

[mick7504]

Thanks to everyone for your input.
Very much appreciated.
Mick

[Sam Green Racing]

They are teflon buttons mick, can't come out like a circlip.

Sam.

Sam, Look again, those are in the thrust surfaces of the piston, like drag racers do. Not anything to do with wrist pins.
KOS

Reply #4 Mark, please wake up.

Sam.

[NitroHunter]

Before modern coatings came on the scene, those Teflon skirt buttons were a common piston crutch in nitro motors. Due to skirt galling, it was not unheard of for cars to go through 4 BOXES - yes 32 pistons - in a race weekend ... and I've seen occasions where THAT was not enough!  
And guys tried like crazy to keep from having to pull the heads...  
 Torco Nitro 70 motor oil was a godsent.