885 head decked 1mm!

[vleivo]

I have a 885 head whicha has been decked 1mm. I have custom pistons so no problem of valves hitting pistons.

What else should be considered with a head this much decked?

My pistons come 0,6mm over block.

I plan to use 2.05mm head gasket so +0,3mm

[ForcedFirebird]

What is the total head height?

Is it 124mm (1mm off a fresh head), or 123.7mm (1mm past the limit)?

Are you using flat pistons, or do they follow the stock crown shape? I have had good success with a 1.22mm distance from the head to the pistons using the stock shape.

[digger]

Cam timing gets thrown out slighty depending on gasket thickness , piston to valve clearance needs to be measured if stock relief depth etc

With custom Pistons on 885 IMO You're better off removing material from the block to get the piston and head tight and bump up the CR , when you take it off the head the chamber gets smaller diameter and the piston dome doesn't mate as nicely. On the 731 and 200 it's fine as the quench area is flat vs part of a dome

[vleivo]

Head height is now 123,7mm.

We are using Mahle street stroker pistons from Ie Motorsport, with deep valve pockets.

We are also using adjustable CAM gear to correrct the skimming of the head.
CAM is Schrick 272

But is there risk of piston hitting head? How about the head itself is it alot weaker when skimmed 1mm?

We only noticed this when head had ported, built and refurbished, so previous owner has Done the skimming, we only skimmed it to be 100% straight.
But as head is now practically good as new we would like to use it despite being 1mm decked.

[digger]

mock it up and measure. you can get MLS in a multitude of thicknesses so its not doom and gloom. my guess is dpending what comp height those Mahle MS pistons are that you will need one just a bit thicker than the OEM 2.05mm

[ForcedFirebird]

Usually the head and piston clearance is more of an issue than valves and pistons.

[vleivo]

Update

Pistons were very close to touching the head. Now the combustion chambers will be slightly modified on one side to give 1mm clearance to pistons.

Compression was close to 11 so even with the modifications to the chambers we will be running a bit over 10:1 compression.

This was also due to the bore being 85mm in my motor and combination of decked head with smaller chambers, with stock bore it might have worked.