When do you use Full floating pistons (bushed wrist pin) vs. pressed wrist pin? What are the trade-offs for one design over the other? Does it depend on the piston or the engine output or what?

 

Anyone? Full floating or press fit? Anyone?

 

They both work the same. Full floating just allows anyone to install a piston on a con rod. Pressed fit pistons need the small end of the rod heated up before pressing in the wrist pin. My big block just got the pins pressed in. The rod ends have a blue tint to them now from being heated up so we;re not talking about a simple propane torch to heat them up.

A backyard mechanic can install full floating pistons with no special tools except a snap ring pliers.

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Stephen's racing page

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block buildup now in progress for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car
91 454SS daily driver
95 Homebuilt Harley

 

Floaters are considered better for high RPM use and other heavy-duty situations because the pin can rotate, so the wear on it is more evenly distributed. There also may be slightly less friction. Plus like Stephen said it makes it easier to tear the motor down and replace parts if necessary, like between runs or whatever.

The down sides include: they're noisier, because that's one more set of things that can rattle around; and the little Spirolox rings that they use aren't the most reliable things in the world, especially when re-used. Somebody used to make Teflon buttons that you could use with any pistons since they don't require the groove for the Spirolox which would otherwise have to be cut, but I haven't seen any of them for a while. Also, this requires some method of oiling the small end of the rod a little better than it would otherwise be oiled, to prevent the floating system from galling.

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"So many Mustangs, so little time..."

 

Thanks guys. I'm going to go with the press fit based on the above info. Less parts to screw up. Pressing in the pins won't be a problem for me.

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'83 Trans Am. 400 CID, 224/234 crane cam, Summit aluminum roller rockers, hand ported intake, home bored 2.09" (53mm) throttle bodies, MSD 454 injectors(75 lb/hr), Holley 255LPH fuel pump, custum modded FPR w/Vacuum port added, Edelbrock TES headers, empty cat, SLP 3" stainless steel cat back, stock ECM & chip. Borg/Warner T-5 World Class, 12" Corvette rotors and clipers, GTA 16" wheels, South Side Machine subframe connectors, 1LE sway bars, 3.45 ring and pinion, Alpine sound.
Best E.T. 13.532
Best MPH 102.24

 

Sorry for bumping up a really old thread, but I thought it would be better to ask here instead of making a new thread.

Is it possible to use a piston with floating style wrist pin on stock Chevy SBC connecting rods? As far as I know the stock piston/rod is a press-fit style.