Wanted:Mark25 oversized pistons and rings

[fu-lynn around]

I'm in need of 2 pistons w/rings(flattop or deflector) for a Mark25.
It is bored out .040" over(2.4775"), any help would be appreciated.
Steve

[Mark75H]

Neither Merc nor Wiesco made pistons that size. Pistons for .040" over are going to be very very hard to find (I would predict you will be waiting quite a while) and probably cost you at least $150 each and may be semi finished requiring some machine work. Is the motor really worth that much? Wouldn't it be easier & cheaper just to find another std bore Mk25 or a Mk28?

Another alternate would be to have new sleeves installed (I think Jim Ruck does this for about $110 per cylinder) and go back to std bore .... but I think that would cost more than finding another good block, too.

If you are really dedicated to that block you might try boring it to 2 9/16 and using Mk28/58/78 pistons. I don't know how much 'meat' there is in the sleeve, it might work, or it might go thru to aluminum.

Flat pistons will probably drop your Mk25 to about 9 hp, you have to stick with deflector pistons.