11-18-2006, 08:37 AM
Join Date: Dec 1969
Location: Buffalo, New York
1. Can you get pistons in either press-fit or bushed?
The pistons are the same.
2. Bushed rods must be used with bushed pistons?
See above, it's the rods that differ.
3. Pressed rods must be used with pressed pistons?
4. Do bushed rods and pistons require pressing in any way shap or form or is it like snap rings or similar?
All pistons need some form of pin retention (SPIROLOX, WIRELOX, PIN BUTTONS).
5. What are the advantages or disadvantages to bot pressed an bushed?
Most stock wrist pins will be held in place by an interference fit. A press fit pin is harder to assemble and disassemble. If the rods have been shot peened or heat-treated, you should not heat the rods to assemble them. It is very hard to press a pin in or out of a rod without doing damage to the piston. For most street engines a press fit will work fine. In higher output engines, the heat in the piston can arc the piston more and require an extra 0.0005" pin clearance to prevent galling. Full floating pins eliminate the need for this. It is possible to use a full floating pin with a stock rod, but we run into the question, is it worth it? If it's a drag only car that sees very few miles, the rods can be honed out so the pin rides directly in the rod. With good oiling, this steel-to-steel fit can last a long time in a drag car, but shouldn't be done in a street engine. If you want to bush the small ends (you must have a good set of rods with enough meat around the small hole) you have to bore it .050" oversize to accommodate a .025" wall bushing. Some engine builders drill holes in the top and bottom of the pin bores for oil, but this can weaken the rod, it's better to just file a .010" slot on each side of the bore to let oil in (this works whether you use a bushing or not).
'95 Z-28 383: Procharger, nitrous, etc. BBC 27T race car. "Every man dies, not every man really lives" William Wallace (Braveheart)