What ive found with taking out fro the Geo Dome is you get a few things happen
1 Lower geometric compression = Higher RPM and slichtly less torque
2 Cooler temps from the head
3 Greater turbulence in the cylinder which promotes responce and fuel economy
To what degree of improvements depends on the individual situation. I tried the Multi cut about 4 years ago with a P5 off road engine , I cut about 4 head buttons and each week i gauged their results by swapping out for each race meet. I did this with a standard and turbo button and found the greatest gains from a single notch in a turbo facing the exhaust.. BUT ! i tried a 3 notch in a standard head button.. 1 in the front above the front intake port and 2 on a 45 deg andgle towards the exhaust. I then cut back the head button .2 mm to reduce its standard ratio and took a .2 shim to bring it back.. ..
I was a mennace ! it sounded like a rotary engine lol It created a lot of torque and great top end .. But rear bearings and rods wore very quickly..
Engine development manager Rifling Pty Ltd. Nitro fuel designer : Neo + World record title holder 2012 Austalian Nationals 147.6 KPH , 1 st 2 nd and TQ Australian National Buggy titles 2012. Victorian State title 2012 Neo + , South Australian state title ON and Off Road 1/8 2012 Neo + :-) QLD State Titles 2012 1st buggy & trruggy + TQ Neo + MG66 RX7 1st Sportsman Class Truggy QLD State Titles 2012 !! Nitro Addicts Australia . com