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When raising the exhaust port for more power /performance on the omc 56 cu in "oval port" , where is the raise
to be taken from ?
i.e where exactly is the starting point of the grinding.
Obviously both sides need to be identical, and the port still needs to be of an oval shape.
But exactly what is done to do this ? is it a case of drawing a map and taking the whole top half of the port up 50 thou?
or is there a particular place to start the grinding point.

the very top can go up to make the port 1.450 the same as the sst60 spec, to get this its just 50 thou up (1.27mm).
the chamfer will be going back in.

if anyone has done this could they please let us know how you got on or post pics etc.



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Ok so nobody seems to know what I mean.

ok try this.
when grinding away at the oval port would it be best to grind to shape A or shape B.
Either way it will get a chamfer put back on the top, and at more angle than original.
The exit behind the exhaust port will also be polished as best as possible, as would the inlet ports.
Inlets do need a clean up and slight grind as there is a bit of roughness and very slight mis-alignment.


Also been wondering if its worth taking the sleeves out to do a better clean up and polish block job, and then just press em back in when done.

I am thinking just put the block in the oven (when the wife is out for the day) to pull the sleeves out and have a proper
clean up of my spare block for a practise run.
put sleeves in freezer over night and heat the block to replace them.

well I thought there would of been plenty of opinions on this subject.
the place to start and stop the raising of the oval I would of thought is critical to both power and longevity.
I think ill just grind the top 75% and take a chance on it being good enough.
I am not after a pure race motor, just a little bit more performance than a standard 70hp motor.
by that I mean start at about the yellow line and finish the same on opposite side of the port and make a steeper fuller
chamfer once cleaned up.