Compression

moper said

Thanks Ram...I'm at 0' elevation...lol. You guys can "get away with" some higher ratios, but I'd still prefer living near the shore ;). A note on the .040 distance. I've run as close as .030 with good pistons, good crank, and steel rods. I know of several racers who run as tight as .027, but they can read the piston part number stamp like a mirror in the cylinder surface. They actually barely touch at 7K rpm. At least, that's what I am told. Generally, .035 to .045 is what you want. The closer, the better the effect.

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On higher RPM engines you need more than .045 at times.I had a .060 over 440 with a set of Arias domed pistons and 516 Heads that had .100 milled off of.I had to put a .124 gasket on to keep the valves from hitting with my .650 Flat Tappet cam with 290o Duration at .050.
Now on the HEMI's it is a complete different Geometry to do to keep the valves from Over-Lap collision.
I have had a 501 C.I. motor with 62CC INDY Cyl Heads with a .692 Roller with 286o Duration at .050 and had the piston .020 out of the hole and a .042 gasket leaving .022 piston to head and .030 piston to valve clearance.I broke a rod in this motor and later come to the conclusion that the $800/set rod broke because of hitting the valve(impressions of valve on the pistons)on the piston.

But as for the Gas your buddies used in the 60's on there 383 it had a little thing in it that we don't use anymore in gas at the stations:LEAD(hence the word UNLEADED).Without the LEAD in the gas the molecules burn at a lower rate and therefore have a cooler burn rate and fewer unburned gases going into the air.It also makes a motor without hardened seats in it burn the valve seats,valves and guides out a lot quicker.