Correct piston to wall clearance on weisco pistons?

[Over-Easy]

I've got a mid eighties 70hp 3cyl. omc, that is going to be bored to .040 over, but, I need to know if the weisco's require a larger clearance. Also, how much can I cut off the head and still run pump gas?

[Rickracer]

:cool:

[Jay Smith]

Loose .008".........

[Travis Fulton]

i had 75 thousandths cut off of mine, that left me w/ a cranking preasure of 155 psi. i still run pump gas, didnt notice a tangable diffrence so i dont know if it is worth doing again, i would talk to jay smith or anthony Mc culloch, about it :D hope that helps

[MODIFIEDOUTBOARD]

Some of the new Wiseco pistons are coated on both sides.
We remove wiseco's coating and then bore/hone cylinder to reccomended Wiseco clearance for the 3" or 3-3/16" bore piston (0.008) and then have the piston skirts and domes coated.

COMPRESSION?

Milling the three cylinder head will adversely affect the SQUISH VELOCITY(Milling reduces it too much)) 0.030max is common

SQUISH VELOCITY- Measure of the speed at which the compressed fuel air mixture is swirling as the piston approaches TDC. If Squish Velocity is....
(To High Detonation/Melting/Seizure, To Low poor performance)

What engine parameters affect SQIUSH VELOCITY?
Bore,Stroke,Rod Length,RPMs,Exhaust Timing,Squish Clearance (Piston/Head Clearance), Trapped Compresion Ratio and
Squish Ratio(Cylinder Head Geometry or shape).

The "OMC triple" cylinder head chamber geometry does not lend itself to milling. The Chamber geometry requires modification in order to maintain/improve the Squish Velocity of the engine.
We insert domes into the cylinder head to correct the Squish Ratio, the Hemi shape also improves combustion efficiency.

Inerested [email protected]
Anthony McCulloch

[Over-Easy]

Thanks for the replies. I'll have to see if the new pistons are coated or not. MODIFIEDOUTBOARD what does reworking the head like that cost?