Piston Protrusion

[Rigmover]

Hello,

Ive had to have my block on a 2008 OM642 engine machined by 4 thou due to an imperfection on the surface, I'm trying to find the maximum allowable piston protrusion when using the standard head gasket. Ive come across a reference to the following statement "Piston Protrusion should be between 0.38 to 0.62 mm". After many hours of searching through WIS/ASRA I can find no documentation or reference to the subject for my engine.

Does anyone have any firm data on this subject.

Thanks

 

[hmang]

Hello,

Ive had to have my block on a 2008 OM642 engine machined by 4 thou due to an imperfection on the surface, I'm trying to find the maximum allowable piston protrusion when using the standard head gasket. Ive come across a reference to the following statement "Piston Protrusion should be between 0.38 to 0.62 mm". After many hours of searching through WIS/ASRA I can find no documentation or reference to the subject for my engine.

Does anyone have any firm data on this subject.

Thanks

Is there a non -std head gasket available ? + 0.1mm would be the easy way to put it back to how it was . Otherwise you've got one bank different to the other .
they might be in spec but if you get any running issues , you'll always have that doubt . If it ran ok before the skim , why change things ?

 

[LostKiwi]

Can you get the pistons skimmed .004" to compensate?

 

[Botus]

4 thou - I doubt the car would ever know

if it was a two stroke and u pushed the squish under 25 thou, intended to run on 2 star and then abuse it - I be concerned...

bolt the head on

 

[oigle]

4 thou - I doubt the car would ever know

if it was a two stroke and u pushed the squish under 25 thou, intended to run on 2 star and then abuse it - I be concerned...

bolt the head on

Totally agree. 4 thou is nothing.

 

[mioba]

Title sounds like a naughty movie.

 

[Rigmover]

Thanks for the replies.

After spending hours and hours searching the WIS I finally found the specs for the engine, for anyone who has the same issue in the future the acceptable limit for piston protrusion on the 2008 OM642 is between 0.53 - 0.77 mm which works out at 20.87 - 30.30 thou giving me an allowance of 9.43 thou. Once I get the pistons in the block I will be able to get a measurement to see if its still in tolerance.

Regarding machining the indent in the piston, I dont really want to go down this route, the piston tops are coated and I dont really want to disturb the coating

Ive been in touch with the local suppliers for head gaskets and they have no information on a thicker gasket, but there does seem to be one option from Chrysler, they have a Jeep (CRD) which is also powered by the OM642 engine, apparently they have oversized gaskets for their cars.