m50 deck height

[ross_jsy]

Does anyone know the deck height of an m50? Need it for calculating compression ratio for new pistons. Google says either 210 or 211mm.

Cheers

Ross

[rich318i]

depends on what head gasket your using i guess

What compression you aiming for?

[ross_jsy]

Well yes, head gasket thickness does effect compression ratio. I am trying to find a piston from the Wiseco catalog that will work with an m54b30 crank and 135mm rods. They don't offer a b30 piston, however they do offer a b25 piston. I calculated it using a 211mm deck height so:

211 deck height -
89.6 stroke /2 = 44.8
=166.2 -
135mm rod
=31.2mm
Piston has a compression height of 27.81 leaving a 3.339 deck clearance

Putting that data into a compression ratio calculator along with a 33cc cylinder head volume and a 1.75mm stock gasket (I need to measure my old gasket to check this, but the net seems to agree that is stock crushed thickness. m54 gaskets are about half as thick) gives me a static compression ratio of 8.3:1. I was aiming for 8.5:1 so I can live with that.

But if it's a 210mm deck height the CR rises to 8.96:1, higher than I ideally want.

I don't want to go down the thicker MLS gasket route so I can use a stock gasket and cutter rings, hence trying to find forged pistons that will take me to the ideal CR with the m54b30 crank.

[ross_jsy]

Found the piston I need. 27.75mm compression height and a dish up from 7cc to 8.8cc drop the CR down to 8.57:1. This was calculated based on a 210mm deck height though, which a few sites seemed to have confirmed

Would anyone be able to run through my maths before I commit?

[DanThe]

I have a block on the floor at work Ross, will put a tape on it today for you

[ross_jsy]

Cheers mate much appreciated