Well i was looking at the piston to wall clearance and it looks kinda big. The shop foreman said it was ok, but its bugging me. These are 81.5mm cp's. . I figured it might be ok because it does not move at all front to back just side to side. Anyone?

I dont have a gauge to read diameter of cylinder. The guy took the reading at the shop and one cylinder showed up at 81.3~ bore up top. He said this was within spec.

 

The pistons are tapered slightly. Piston to wall clearance is measured near the bottom of the skirt.

 

That's correct.

 

Yup, it looks good!! My does the same thing on 81.5mm CP pistons!

 

Sounds about right...

I measured my piston-to-wall clearance by placing the piston upside down since I didn't have the extra long thickness gauges. Besides, doesn't CP have good repeatible pistons that are accurate to 0.0001"? I wish I knew about them when I rebuilt my engine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blaze the chemi &raquo;</TD></TR><TR><TD CLASS="quote"> Besides, doesn't CP have good repeatible pistons that are accurate to 0.0001"? </TD></TR></TABLE>

A wiseman (R.I.P.) once said that CP pistons are so accurate that he can hone the block and drop them in without even needing to measure the pistons.

 

Thanks guys. I feel MUCH better.

 

dont worry about the movement, it is probably built a little loose for boost. We just pulled the head off my friends 85mm car and his pistons have side to side play also with his CP's.

 

Have you installed all pistons yet? You might want to check and measure it yourself.

 

all pistons were installed by a reputable local shop.

 

CP pistons are built with the clearance built directly in them. This means that the pistons on a turbo app. actually come 3.5 thou. smaller then the desired bore size. So when you bore and hone a block for 81.5mm, the machine shops job would be to put the block right on 81.5mm and not even a hair larger. If it was, you would have too much clearance. The motor will run if it is larger, but that is when you start to hear noise.

 

That's for sure

 

y not measure the bore?

 

I always take the pistons when i take a block to get bored/honed at the machine shop, tell them what piston to cyl wall clearance I want and its done with, perfect everytime

 

It seems a tad loose to me, but I'm guessing you don't have them on the rods or rings installed either. I gave my wisecos ~0030" clearance, and I've yet to hear any piston slap on cold startup. I've also burned zero oil over the total of 2146 miles I have so far on them.

 

mmmm if CP pistons have the clearance built in, then why do they send instructions with them on figuring up your clearance?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SPOOLINmatt &raquo;</TD></TR><TR><TD CLASS="quote">mmmm if CP pistons have the clearance built in, then why do they send instructions with them on figuring up your clearance?</TD></TR></TABLE>

They do not give recommendations on figuring bore clearance, they give you recommendations on how to file fit rings on one sheet. Then they give you a sheet on piston specs. Last they give you a sheet on what grit to hone with and how to finish the hone aka plateau. They do not offer size as or clearance as that like I stated above is built directly into the piston