Thread: How to get Pistons off Rods?

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Hi guys,
My project is coming along nicely, got my 492 heads nicely ported, now comes the second load of shopping:
What style pistons should I get for regular, lightly tuned road use? I'm going for hyper, 4.060 bore, coated skirt, 2 valve relief flat top ones.
But how the hell do I get my old pistons off my old rods and the new ones back on? How do you "float" pistons? What is easier to do and what lasts longest? What about these snap-ring fits? Is it better to use press-fits or floating? Is there a difference between floating and bushed? Never thought of problems that might occur when changing pistons, but I definitely want to get that CR up to match my cam, got 18cc dishes at the moment
Thanks for any help on dismantling the moving parts,
Mad

Piston pins are simple: they are either a press fit into the pistons or a slip fit into the pistons. The slip fit is referred to as "floating" where the pin "floats".

Pressed pins and floating pins both are a slip fit into the piston. If the rod end has a bushing installed in the bore, it is a "bushed" rod. Floating pins have a small oil hole drilled into the top of the rod.

To retain the pins in a floating installation, a retainer clip must be used. This can be a circlip, a spirolox, a retaining ring or such. All allow the retainer to be removed for pin removal.

For a street driven vehicle, there is no big advantage to floating pins. Floating pins are convenient for when the engine is disassembled frequently....like a true race car.

Your local engine machine shop can press the pins out of the piston/rod for a really cheap price or you can do it yourself if you have access to a hydraulic press.

ok, here goes!

Not exactly sure of the procedure on how to get the pins off the rods, but being as you have to heat them to press them on, im sure u heat them to press them off... Just take the set to a machine shop, they should be able to either a) do it for you, or b) tell u how to do it.

When refering to a "bushed" rod, they are speaking of using those snap rings to hold the pin in the piston. The bushing in the rod allows the pin to rotate without being metal to metal. A bushed rod with a moving pin won't make metal inside the motor like a pressfit rod would if u tried to use the snap ring method. Be cautions when buying parts because Press fit pistons will not go with bushed rods. Also, the snap ring pistons won't work with pressfit rods.

I'm not exactly sure which method lasts longer, but i really like using the snap ringed pistons because I can do it myself, without heat, and it doesn't really take any special tools. Maybe a small screw driver to snap them in.

I really like the spirolox, they aren't hard to put in and they are really durable.

Ok, im not exactly sure if there are different piston types, i thought the pistons that require snap rings have grooves for them and pistons that require press fit rods didn't have grooves. I'd like to find that one out. Learn something new today!

to get the rods off you need to press them off with a rod press heat will not do . to put the new pistons back on the rods. the rods should be heated in a rod oven to hang the new pistons. have them check to make sure they are not bent or twisted. if you float them the rods will need to be bored out. this can be done on a mill with a boring head and then bushed and brunished in. this can be done two ways with a sunnen bushing expander or ball broach just press them in will not do. they need to be expanded in every valley of the rod bore for 100% heat transfer and this locks the bushing in the rod and keeps the bushing of getting beat out . then they need to be honed out to.0005 -.0007 they will need oil so you will have to drill a small hole on top of the rod with a chamfer on the oil hole . the hole should be done after expanded of the rod bushing. they are made from tuff bronze to drill the bushing you will need cobalt or solid carbide to drill the bushing this is alot of work. on the locks there are many ways to lock the pin. buttoms. tru-arcs double spiroloxs round wire locks. but if the pistons are not cut for locks they can be but this is a lot of work and like said you will not need it