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Old 06-23-2014, 12:52 PM
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Davezilla Davezilla is offline
Motorized Bicycle Elite Member
Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: What mod should I get.

It's a way to get more compression out of a stock head, it can be milled down, but since it's small and pretty easy to do by using a piece of sandpaper over a sheet of glass, you can sand away about 1mm or 040" to boost your compression up and it'll give you more power.
The idea is to close up the squish clearance between the piston top and the combustion chamber so there's only about a 1/2 to 1mm gap between the piston crown and the combustion chamber, you'll also need a compression tester so you can target for about 140 psi cylinder pressure, but typically, you can shave off about 1mm safely without going too far on a stock head. On the performance heads tho it's better to use thinner head gaskets like the copper ones Juice sells, but on the stock heads, they need all the help they can get since their combustion chambers tend to be huge...
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