piston question

[bansheedemon]

So i was told my banshee was a 397, but i took a camera in and looked at the pistons and the writing on pistons were 3m065. Which im assuming it means its bored to fit a 65mm piston? i dont know what the 3m means though.Thoughts? And bored to a 65mm would make it a 358 correct?

[toytech]

65mm bore and a 4mil crank make around 397cc.

[bansheedemon]

that would be nice. But im assuming no way to check crank without tearing into it? i have ridden stockers and.its.considerably faster than a stock shee. And anyway to tell what brand pistons?

[Starwriter]

Poke a pair of calipers down the spark plug hole and measure the stroke. If you don't own calipers, use a stick.

[bansheedemon]

Ill give it a shot when i can. Any chances the 3m is for a 3mm stroker possibly? i have heard vitos makes one. I looked up the number on the piston in google and got nothing.

[Starwriter]

Pistons don't have anything to do with the stroker. There's long rod pistons and short rod(stock length) pistons.

[bansheedemon]

I know. The numbers on top just look like they were put there by the builder. Just didnt know if it could.be a reference. It was supposedly professionally built. But i wouldnt know since.i didnt have it done. I trust who i purchased it from, but without a build.sheet its.hard to know.what you really have. Ill try and figure out stroke when i have a chance.

[blue97shee]

the 3m may be whats left of the wiseco number.  513M65.00

[blue97shee]

or 513m065...sorry

[oldskool]

prolly says 513mo65(stock wiseco piston), but it can still be a +4 mill crank with short rod making a 385cc

[bansheedemon]

The numbers are all the way across piston. No more room for other numbers. Ill look into it more and measure my stroke as well.

[bansheedemon]

I did a compression test and both were right about 175psi. Whats the compression for a 4mil stroker roughly?

[Jereme6655]

you have to measure the stroke.  You cannot tell what length rod your crank is based off of compression as I can take a stock crank and rechamber the head, or get an aftermarket head with interchangeable domes and make my compression the same as your.  Shit, my stock stroke 350 dune/play port motor had 172 psi on each cylinder with 19cc domes.

[bansheedemon]

Gotcha. I have been trying.to measure my stroke. But its being a pain in my ass. Keep messing it up, and getting different readings.

[Starwriter]

Gotcha. I have been trying.to measure my stroke. But its being a pain in my ass. Keep messing it up, and getting different readings.

Take the stator cover off so you can precisely turn the flywheel.