I need help here guys. I have two sets of 90.5mm P&Cs. When I put them next to each other, the stroker one is shorter and the pin is closer to the top of the piston. I asked the dealer I bought them from the following:
Can they be used with the standard 69mm crank? Also how do I tell for what stroker size are they? I mean for a 74mm, 82mm, 84mm crank or what?
The answer I received over email is:
the stroke pistons are for 82mm and higher cranks non stroker are for 80mm and smaller cranks. the strokers can be used on non stroker motors with out a problem

Me no understand :alien. Can someone translate into english please? And can the stroker P&Cs be used with non stroker crank? Technically I am sure they can be used but wouldn't the compression be lower because the distance between the head and top of piston will be larger?
Raf

Is he saying cranks less than 80mm can use the standard P&Cs while 82+ you need stroker P&Cs?

This will open up a can of worms

ok - i will have a go ( i am sure some one will correct me)

A "B" piston pin is further up the top to offset the wider diameter on the stroker crank.

If you didnt and used a A piston it would push out the top of the cylinder.
ie -ve deck height

If you used a B piston on a 69 crank you would have massive deck height

This is also why you shim a stroker under the cylinder. 69, 74, 76, 78, 80, 82, 84 and 86mm cranks and only 2 piston sizes.
I have heard there is a C piston???

It is also why strokers are not a piece of piss to build.

78 and under can be built with A's and shims. Over that and the motor gets too wide and too much shimming.
There are problems with the piston comming out the bottom if it isnt done right either.

You can still build a non stroker engine with "B" pistons, but you need to machine the Barrells down to get the correct deck height, and use 40hp push rod tubes.

The advantage of doing this is it gives you a very narrow engine and a nice light piston.
If you use "B" pistons with a '78mm crank it comes out like a stocker, no machining the barrells and none or only a small spacer to get the deck height right. This is with stock length rods of cause.