2,2 piston/cylinder question

[limble]

Wayne,
I have my engine (2,2) down to the connecting rods. I read in your book about keeping the wrist pins with the same pistons. That makes sense but you also mentioned mix and matching them with pistons to do a little low budget balancing. Were you talking about new parts or the old parts?
The fact that the wrist pins have already been pressed in would make be think that they should stay with the same pistons.
But then given the superior German engineering that was put into these engines make me think the tolerances would be quite tight.
Cast iron cylinders- besides honing them what else do you suggest? The cross-hatching is till visible with very little carbon build up.

Mike

[Wayne 962]

Uhh, you're confusing things. You should make sure that your piston pins are kept with the proper pistons *after* they have been balanced together. Beforehand, it doesn't really matter.

Have the cylinders checked for ovality with a dial bore gauge...

-Wayne

[Wayne 962]

Originally posted by limble
Is it a press or a sliding fit?
I understand the issue about keeping them together after balancing but what about the press fit issue? If a wrist pin that is in the upper tolerance range is swapped with a wrist pin that is in the lower end of the tolerance range then I would think that there might be a slapping issue.

If it's a sliding fit then it would be a non-issue.
I'm not trying to nit pick on this issue but just don't want to end up with a wrist pin knocking.
If this is a non issue I will shut up and go back out to the garage.
I like it better there any way.
And thanks for your help.
Mike Lancial

Piston slap is not caused by the piston pins - it's caused by the piston being too worn in the cylinder. In the old days (the very early 911 engine days), the piston pins were an interference fit, which means that you had to heat the pistons to insert the piston pins. Somewhere in the late '60s or '70s, they went to a free fit. All the sets made these days (except for the NOS ones) have a free fit, so it's really a non-issue.

-Wayne