How to figure out CR of a Piston?

[jrc90240sx]

I have some Custom JE pistons that a Machine shop ordered for me when they built my engine. I need some help in figuring out the CR of the pistons. I wanted 9:1 CR when i had the machine shop order the piston. But sense then the engine is dead and i pulled the pistons. The pistons appear that they might have a much higher CR. I know the stock KAe piston has a slight dish correct? The JE pistons have a dome with valve recess cut into it. I will post some pictures later tonight of the pistons with some measurements. Thanks for any information and help

Joe

Modified by jrc90240sx at 9:54 PM 6/7/2005
Modified by jrc90240sx at 9:16 AM 6/8/2005

[Checkered-Member]

JE only makes 8.2 and 10.5 compression pistons for the KA

So if you have JE pistons with a dome they are 10.5

[jrc90240sx]

That information should answer my question then, but i will still post the pics up.



From the looks of it and if JE does only make those 2 CR pistons it looks like I have 10.5:1 pistons. I dont wish anyone to have to go through what i did with that machine shop.

[jrc90240sx]

Also one quick question, do you guys think there is enough material on top to posably have it machined down to a lower CR like 9.5 or 9?

[Checkered-Member]

I don' know how much they took off, but a 9.0 compression will have a dish on it, that still looks higher then stock I' say something like 10.0

[jrc90240sx]

Yeah, nothing has been done to the pistons yet, I was wondering if you think that they could be machined a little lower, to like a 9.5 or so. I guess we would really need to measure the material at the top of the head.

[Checkered-Member]

This is what I would do, get a used stock piston, and machine this one down until it's the same height as the stock one, so it will give you a 9.5 compressionOr you can get an altima stock piston which is 9.2 and machine the JE one until it's the same height.