Budget 455 build..regarding using stock connecting rods I called Wiseco yesterday and the tech tells me that no problem using stock rods, just press pins and not use the clips to retain the wrist pin. Just trying to wrap my head around this. This works? Normal? I know new H beams would be better. Not a crazy hp build. I was planning to use the L2323F Speed Pro’s I have but considering the Pro Tru’s.

 

Absolutely. The pins are press fit in the rods so they wont move. No different than the stock pistons and pins. You cant use the clips with the pressed pins because there is always a little side to side movement and with the pins pressed into the rods they will beat the clips out.

Only thing if you do this is to make sure your machine shop measures the actual press fit before you proceed. I have found some of the aftermarket piston pins are a little smaller than stock and do not give the proper press fit. The press fit is not much to begin with, typically around .0015" and if the pin is small or the rod slightly big it wont work.

 

The tech probably thought you where asking if the pins supplied with the pistons are ok to be a press fit,, because a lot of pins supplied with pistons that are meant to floated have thinner walls (lighter and better material)and can’t be used in press fit rods.

They don’t have have the wall thickness for that

so it seems that piston and pin setup is ok to press fit on factory style rods

 

This puzzles me. Are all 455 rods press fit wrist pins? If so why would new pistons have retaining clips? There is a fundamental difference between fixed and floating pins, floating pins turn in the small end bush. press fit pins turn in the piston. The piston is effectively the small end bush on a press fit setup.
I don't understand the whole reasoning, but many British race engine builders would convert fixed rods to floating and either machine grooves for retaining clips or use custom pistons. Maybe something to do with lubrication for a highly stressed bearing?. Certainly it wasn't done for fun.

Roger.

 

yes all 455’s are press fit.

307’s and diesels are floating.

The reason they make them for both applications is to sell pistons and to make it easier for them to have one piston/pin setup for both styles

Some lower quality forged pistons for Olds are press fit only, like the old TRW’s and speed pros. I’ve cut them for clips and floated them but only when they were a mistaken purchase by someone along with aftermarket bushed rods.

if you have the option, always float them

the reasoning is reduced friction. For mass assembly line , press fit is cheaper , quicker and easier

 

I personally think the only advantage to full floating pins is the ease of replacing a piston when needed And ease of assembly. Just about all performance pistons come with clips because they assume that guys are using aftermarket rods which almost always are full floating.

 

I agree, and would add that having a steel pin rotating in a bronze bushing is a better design from a wear perspective as opposed to having the steel pin rotating in aluminum. It's mostly theoretical at that point, as I haven't heard of too many issues with the piston pin bosses wearing out as long as sufficient oil was present.