Blaster What is the change in compression for a given amount shaved from head?

[niteridder64]

Just finished a complete rebuild on my 701 61 x. I ported the cyl, raised exh up 2.5 mm and widened a little. Bored 1 mm over. Triton head, do not know cc's. The motor has 0 hrs, was cold w/ throttle open and got 150 ea cyl. What cranking psi can I safely go to w/ a ported eng and run 93 octane? If I can go higher what is a ball park corallation between amt shaved and increase in compression?

 

[TheBuzzard]

why in the @*%# would you raise the ports 2.5mm and not widen them to 65% of the diameter?

 

[niteridder64]

I did widen the port to 70% the diameter

 

[Big Kahuna]

What ski is this for? On a SJ you would not want to raise the porting unless you were looking for Top Speed Only.

 

[niteridder64]

Blaster 1. Can't go wrong for wanting more speed. I lightened the flywheel and will run 180 psi so bottom end should not suffer. I have given the ski 2 heat cycles for a total run time of 20 min. I got 170 while it was hot. I bought a new quality gauge and it read 180 on both, right where I want to be for running 93 gas + a few oz of octane booster. Hoping to get 7000 rmp's after break in- not sure what prop is on it.