I have searched Google dsm forums club3g and a few mustang forums as well for a good few weeks Regaurding this issue / confusion I am having. With that being said. I can't find the answer I wanted. I understand that finding piston to wall clearance can be done using feeler gauge. I personally believe this to be hill jack as you need to measure near but not at the bottom of the piston side skirt due to different diameters machined into the actual piston for various reasons. I'm going with micrometer and telescoping " T " tool method as I have the correct 3 - 4 inch caliper and 3-4" spring " T "bore gauge.

My confusion is on the actual correct way to get the clearance value recommended By J E pistons which in my case happens to be .0037 These are break downs of the two methods I am confused about.

Method 1 :
Piston to wall clearance = (Cylinder Bore size - Piston's diameter) / 2

????


Or:


Method 2 :
Piston to wall clearance = (Cylinder Bore size - Piston's diameter)

ANY help with past experiences with success using forged 2618 type pistons will be greatly appreciated. Thanks.

 

Number Two is correct. The only way to properly check the piston to cyl. wall clearance is with a Dial Bore Gauge. A snap gauge and caliper will not be as accurate. Any competent machine shop will have the tools to do this. I have been boring cyl's for over thirty five years and it is the only way to be accurate. The largest part of a piston is 90 degrees from the pin at the very bottom of the skirt.
Don

 

OK cool .Thanks.

 

I would run .0045 actually.

 

Ok thanks for the advice. The way I decided to go with .0037 is the recommended " Generic " piston gap for my pistons is .0035 and the spec sheet that came with the pistons recommended .0040 . I dcided If I go .0037-.0038 the .0002 difference should be taken care of during the piston break in process and leave some room for increased longevity of the build maybe getting up to .0045 down the road with some miles on it. Thanks again for the advice.

 

What guys think about 2.2 liter CP piston 4G63 block with 0.003 piston to wall clearance with EF4 turbo E85 aim power 500 mustang whp, but break in the engine step by step..

First 1000km wastegate boost rev limit at 5000rpm , than other 1000km 1.4bar and only after 2000km turn up the boost and the ignition table ?! May also use the engine with Cosworth low temp thermostath ? I know 0.003 is tight but dont want excessive oil consuption..

 

any advice ? break in step by step but tighter p2w ?