Pick one : Full floating or pressed pin Pistons ??

[SwaveDave]

If you had to choose between a pressed pin forged Piston rated at 10.6 CR, or a full floating pin Piston rated at 9.6 CR...which would you go with ? Would you go with full floating pin Pistons if it cost you a point in CR ??? What are the distinct advantages of full floating pins on a Piston ???



Thanks, dave.

 

[Jack]

Dave:
This is kinda late. As much as I like this general tech section, I forget to look at it ... look at C3 mostly.

Full floaters are needed for sustained high rpm (less heat & friction) ... or ... if you need to routinely change-out pistons (convenience) ... both factors in racing. For all but the most radical chevy street motors, pressed is just fine. I have floaters in a 388 street motor but it's overkill ... and I sure don't plan to be changing pistons anytime soon. If primarily street-driven and needed 10.6:1 CR ... I would not hesitate to use pressed.

There are some pistons that are designed to accomodate either a pressed into-rod pin or a float in-rod pin (mine'll do either). If you want it to float, as far as I know, you also have to have rods with pin bushings (pins also float in rods) if you use floating-pin pistons. Also, most floaters use spirolocs to hold pins into pistons ... if you're not experienced installing spirolocs, do get an expert to show you how (stretch & preload) ... a simple failure here WILL destroy cylinder wall in a quick minute (a downside of floaters)!

BTW, ALL pins float in pistons regardless of pressed or floater. In a pressed pin piston, the pin is both centered & secured by the press-fit into the rod's NON-bushed small end. In a floating pin piston, the pin is also floating in the rod's BUSHED small end, but centered & secured by internal snap ring-like fasteners (i.e. spirolocs, wirelocs, snap rings) that fit into radial grooves at either end of piston's pin bore. So ... primary design difference in piston design between floating pin or pressed pin piston is whether or not the piston has grooves in pin bores
JACK:gap

 

[Bullitt]

Forgot about this topic, too. BTW Dave, did you ever unload your pistons?

--Bullitt