The issue with running a overly tight head on the car engines is they wont idle down correctly when you let off throttle.... With a tight head they always want to "ring-a-ping ping ping ping" when you come off a high speed pass.......... And the only way to get rid of it is to drown it out by running a overly rich mixture, which substantially reduces the power of the engine............ Some engines these days come with as low as 0.014" clearance and will ring-a-ping ping horribly if you try to tune then to the edge.,...They run like scalded dogs tho , but only if your willing to put up with the ring-a-ping ping when you idle down after a hard pass....

Personally I can't stand engines that do the ring-a-ping ping on idle down... I have spent years playing around with head buttons trying to find the perfect balance that allows my engines to reach warp speed RPM"s, carry crisp throttle yet still idle down smooth and silky after a hard run...... I see far too many engines at the races that ring-a-ping ping piing, to the pint where I believe some people assume its perfectly normal and acceptable....

In the end its a very fine line finding the perfect balance in the head button that allows the engine to make full power and RPM, yet still retain the ability to idle down quick and smooth after a hard pass........