M20B27 turbo build

[Indiana]

Hi, guys, I have been reading for a while and decided to register since I am about to convert my NA M20B27 into turbo.

The car is currently in the garage and is waiting for my decision to start the project.

I am researching about pistons. I would like to use stock pistons since the purpose is not maximum boost/performance. The car should be a pretty fast DD.

The engine is stock M20B25 Motronic 1.3, 81mm crank from 324td and shaved pistons from M50.

Has anyone used M42 pistons into M20? I am about to use these, shave them a bit and enlarge the dish so that CR goes below 9:1. The E30 M42 pistons are forged and the Super ETA pistons are very hard to find in Europe.

[einstein57]

You can get some forged pistons that are the same CR as a stock i for around $650 from brc performance. That what i'm going to be using along with s52 rods.

[Indiana]

BRC Performance is way too far from me. The pistons will be the ones from M42.
Is it going to be a problem if the pistons go 0.45mm above the deck? The stock head gasket is 1.75mm thick when compressed, right? So there is still piston to head clearance of 1.3mm. should I remove this 0.45mm from the piston's top and make it flat to the engine block?

[Ian Bowers]

E30 M42B18 pistons are cast, whoever told you they were forged mislead you.

[Indiana]

OK, I switched to late M40B18 pistons which have a pretty nice dish. However they are still 0.45mm above the deck. Should i remove 0.45mm from the top of the piston or it is fine that it is above the deck?
As I said the head gasket is 1.75mm, so the piston/head clearance is 1.3mm