Van

Hehehe. That would be a pretty trick mod!

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)

sweet9fortyfour

Pulling trucks are tested for cubic inches. They back the rockers arms off and check the volume of air the piston moves.

GodSpeed

My head is shaved. ohh wait, we are talking about engines here. nvm...

apierce918

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?

V2Rocket

I shaved mine .003" just to get the remains of my old headgasket off X_X

It's on normal timing and hasn't been a problem.

KuHL 951

Now don't get greedy and take too much off-JK

apierce918

i also saw anything less than .020 then you will be ok, other variables will move it nearly .020" like belt stretch + heat expansion

Van

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.

apierce918

thanks, i'll slap it on in a little bit here with the regular marks and see how it goes this time...