Details to convert pressed piston pin to full-floating?

[pishta]

look up teflon buttons...seriously, hundreds of Aircooled/motorcycle guys run them.

 

[nm9stheham]

I am aware of them. I have read of claims of bore wear with them.... but am not sure how bad it really is. (I suspect crud in the oil or from the chambers.) I am leaning back that way at this point....

I've been thinking that set screws will push the pin up to the top of the bushing but leave that tiny gap under the pin in the bushing. That could allow slight rocking of the pin on the set screw. That does not seem good...

 

[Krooser]

If the set screws held, why not? Is it not done due to weakening the small end of the rod? Or just harder to install in a production environment? Or just prone to fall out? (Perhaps some expansion problem waiting to happen?)

Not trying to be obnoxious at all... but grooving piston pin bores is not free or doable in a home shop, and if the grooves are done wrong, the lock rings are liable to come loose.

I wouldn't want little pieces of steel floating around the oiling system... if one drops out you may get lucky... or you may not.

Grooving the piston for locks can't be very expensive...pretty simple deal to machine.

 

[Krooser]

 

[dibbons]

Does anyone know if the factory small block piston pins are the same part number for full-floating and press fit applications? (i.e. would a full-floating 340 and press-fit 360 factory piston pin be the same?) Why am I asking this: I just pulled a connecting rod and pin out of my 10:1 molasses/water mix for de-rusting and it appears the molasses did a number on the chrome finish of the piston pin. Thank you.

(P1182 would be a TRW part number, but don't know if it is universal or for floating or pressed pin specific applications)

 

[Marcohotrod]

318 340 360 = same pin

 

[pishta]

Its the little end finish that says press fit or floater (bushed) so yeah, same pin. If you think the teflon button is going to wear the bore, just look at the skirts that practically ride the bore 100% of the time. the same hydrodynamic wedge is going to float the buttons as they float the skirts.
"....Any wear from a teflon button comes from grit in your engine getting trapped or imbedded in the teflon. A proper filter, changed often prevents this. In this case, teflon isn't the cause..." and if you have that much grit in your oil, I think youll have other issues than buffed cylinder walls. Also remember that the buttons do weigh more than circlips so take that into consideration. The buttons fit when you can feel drag on the rod rotation in the cylinder. clearance to suit.

 

[nm9stheham]

318 340 360 = same pin

Except for the early 318 pins for the lighter rods, which are a bit heavier. My notes say 154 grams for all of the later LA pins and 161 grams for early 318. The 273 pins are heeeeavy, like around 220 grams for the 2 BBL and 184 grams for the 4 BBL. Diameters are all .9842" from all I have ever been able to find.

Weigh the pin(s) that you have and get one to match that weight.

 

[dibbons]

Just measured the oil hole in a set of custom small block connecting rods I have (Cunningham), looks to be about 5/32". It is so large, the chamfer is minimal. I am not recommending this diameter, just something more to think about. Actually, I might just forget the "hole" idea for a street motor with stock rods.

 

[pishta]

thats puurty! I'd run em....

 

[famous bob]

Ha, that's what I told a friend who then proceeded to let the drill slip and put a nice hole all the way through the palm of his hand.

agree w/ drilling a small hole and chamfer the edges.
Have had an 1/8 drill get me, they tear up a lot for their size, painful!