Head Shave 0.010 = How much compression Bump? 8v motors
#16
Rennlist Member
Originally Posted by ryoji
But one can shave the top of the block as well, if he choose to do, instead of a head.
Do you think anyone is using a stroker crank to get more compression? Even with a stock spec head, if the piston is physically moving a greater distance, the compression ratio will go up.
True that would be blatent cheating, but hard to discover -- is there any way to measure displacement with a tool like a compression tester? (my guess is no, because it would require the valves to open and close at TDC/BDC)
#19
Addic
Rennlist Member
Rennlist Member
digging this back up, i have a question. i have heard now on a couple of occasions that after the head being shaved, you need to change the timing, well, when i took my head in, they ended up taking .008" off. how do i know what to set the timing to?
#23
Rennlist Member
Yes, with these small values, I wouldn't worry too much. (Although it could be fun to get an adjustable timing gear!)
You can calculate the extra degrees of rotation on the cam by using SIN (angle) = (head shave amount)/(radius of cam gear)
I don't remember the exact diameter of the cam gear -- but, lets say it's about 5 inches. With an 0.008" head shave, the rotation of the cam shaft would be off by about 0.2 degrees. My hunch is you'have to be in the neighborhood of a few degrees before it's really going to make a difference.
You can calculate the extra degrees of rotation on the cam by using SIN (angle) = (head shave amount)/(radius of cam gear)
I don't remember the exact diameter of the cam gear -- but, lets say it's about 5 inches. With an 0.008" head shave, the rotation of the cam shaft would be off by about 0.2 degrees. My hunch is you'have to be in the neighborhood of a few degrees before it's really going to make a difference.