What is the difference between full floating,Pressed, and Bushed rods? What does all this mean and which one is stock on a SBC?
Thanks

 

Full Floating = the piston pin has a ~.002 diameter smaller than the piston pin bore on the smaller rod end. Clearance fit. You need to have locking clips to keep the pin in the piston pin bore. More for racing, performance applications.

Pressed Pin = the piston pin has a ~.002 diameter larger than the piston pin bore on the smaller rod end. Interference fit. This is the OEM type and doesn't require locking clips. Used for low-buck and mild performance applications.

Brushed Rod Ends = deburred, from my understanding, to alliviate stress risers caused by casting flash. (could be thinking of something entirely different here)

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

[This message has been edited by MRZ28HO (edited October 05, 2000).]

 

Bushed is a term meaning that the rod has a bronze bushing installed for full floating or semi floating piston fit. Stock rods are not usually bushed.

Full floating is when the pin floats in the piston and the rod floats on the pin. Keepers are used to keep the pin in place. I like to see .0005-.001" pin to bushing clearance. No more.

Semi-floating rod fit is when the rod is press fitted to the pin. The pin then floats in the piston. A .001" interfearance fit used.

Semi-floating piston fit is when the rod is press fit to the piston. The rod then floats on the pin. A .001" interfearance fit used.


Full floating is generally used in performance applications because engine disassembly is frequent. It's much easier to disassemble pistons with keepers than a press fit assembly.

Mike



[This message has been edited by md (edited October 05, 2000).]