Inlet Manifold...Where?

[jonbills]

I bought them off Pete about a year ago. Carlos Fandango Pistons

Are they Carlos Fandango flat tops, or do they have bowls or even domes?

To attempt to answer the question about how much skim gets you how much compression, on my E88 head, a 1mm skim took the chamber volume from 43cc down to 36cc. (and I imagine similar for N42)

 

[SKiddell]

As a guide
On an unwelded N42 I wouldnt go over 11:1 (unless you had an intruded crown piston matching the chamber)

What throws this out is the dynamic compression figure which is a factor of the cam phasing and is tricky to measure without modeling software...this is typically around 7.5:1.

To get the best out of an N42 (compression wise) the "ramped" squish area needs to be built up with argon welding to create a flat zone and a kidney shaped chamber, this will improve squish and air/fuel mixing and help mitigate detonation allowing compression ratios 13:1 +

 

[vipergts]

OK

That's where I thought it should be.

I don't think we are going for big horsepower, just a nice torquey lump

These are the pistons spec

JE custom made forged pistons.
88mm so +2mm on stock. Cutouts in pistons to allow use of big lift cam if needed.
Brand new with rings. Fully floating pins and retaining circlips.