Interference motor means the valves can hit the pistons if the timing chain or belt breaks. Clearance motors allow the crank and cam to be in any position and they wont hit. Neither one of these types of motors mean that you don't have room to work. Just because there are valve cutouts doesn't tell you how close they are.

We don't have any idea if under normal operation the valves are too close to machine and raise the compression. You can check for it when you take the head off. You apply a little clay to the piston where you suspect the valves will hit and then reinstall the head, cam rockers and chain and turn it around twice. The valves will push the putty down so you can check how close they come. If the piston is thick enough, you could grind a little off. For the purposes of checking, you might be ok using the old gasket but you need to make 100% sure there is no dirt of globs of carbon on the gasket, head and jug.

Mickey probably does this blindfolded, during his breakfast. I would say it is one of the principal things he does when creating a high compression and/or big bore kit for us.

 

which leads me to ask----at 100 hours I will be checking my valve clearances--what is optimum?? Can any HP gain be gotten from valve clearance?? I have always adjusted valves to the minimum or tightest clearance specified--I saw in another thread that this was not the right way---all specs for 360-650-700 give a 5 degree variable. any comment?