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does anyone know of any tests done to test this theory? just curious because the shape of .020 of bore could affect the flame front differently from seeing that .020 in a head gasket correct? not saying would, just saying could. be an interesting test to see none the less



I've tested this but in a laboratory and not on a Mopar engine or in terms of drag times, unfortunately. It was during engine development for an Jaguar engine. Burn duration is measured in 10-90% burn time. What was found was that when the squish was maintained at 0.9 to 1mm (35 thou to 39 thou) there was a measurable improvement in burn duration of a couple of degrees. This manifested itself as less ignition advance required when optimised for best torque. Once squish clearance increased to 1.2 to 1.3 mm (47 to 51 thou) you ended up with a flame front quench zone which was detrimental to combustion (forming a rich pocket) and in some cases was a source of detonation. Effective squish not only depends on the clearance but also the stroke length/mean piston speed. This means that squish is more effective on longer stroke engines, such as the older Jaguar AJ16 and less effective on the shorter stroke motors such as the Jaguar AJ26 V8. I would venture to say that it becomes more effective once a stroke length of greater than about 90mm is used. In our case our RBs have a healthy stroke of about 95mm as standard



I wasnt referring to the squish itself but as to were its found. Such as a piston being .020 down in the bore and using a .019 head gasket vs. 0 deck piston and .039 head gasket, all else being equal.