Thread: Help Me Pick Some Heads For Christmas Present

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0.035" to 0.045" is considered ideal. Famed automotive journalist and engine builder David Vizard has stated that the closer he makes the squish/quench, the more power the motor makes, as well as insuring against detonation. Of course there is a limit, where the piston crown contacts the underside of the head and the game is over. Smacking the head will begin taking out the bearings and unraveling the piston. It will also smash the ring lands and capture the rings so that they can no longer function. You know how the piston part number is stamped into the crown of the piston? I have seen that number transferred to the underside of the head due to contact. if you can get it that close without lifting the head, you have achieved the ultimate squish/quench in my opinion. This would likely be in the mid to high 20's, depending on rod and piston weight and rpm's.

There is pre-ignition and there is detonation. They are two different things.
Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

By the way, one very nice tool for your garage is a glass cc burette. Nothing inspires confidence in an engine build like absolutely knowing the volumes you're working with....If you buy a kit, buy a glass burette, not plastic.....I used to use Isopropyl alcohol from the drug store and food coloring from the grocery.....red, blue, green..take your pick.
https://www.summitracing.com/parts/pow-pow351150

P.S. You can offset the cost of a kit by cc'ing heads and pistons for other builders. Ask your local speed shop if you can hang a poster. that could turn into a very nice after-school job for your son. Post ads and pass the word at local roundy-round tracks and drag strips, NAPA, Autozone, burger drive-ins, etc. Anywhere car guys congregate.
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