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Bundyroy wrote:
Quote:I’m pretty sure I understand what you’re trying to do but have a couple of questions.1) By shave the head I assume you mean machining down the flat mating surface on the head so that the compression goes up due to reduced volume at the top of the stroke. Correct
2) By shaping I assume you mean that the domed part inside the head is machined away (as well as mating surfaces) to a better shape to allow for better fuel burn.Correct
3) None of this will effect the distance that the spark plug screws into the head, so is the distance between the end of the spark plug and the piston the limiting factor or is there changes that can be made here too. Yes may have to pack the the spark plug out a couple of mm
4) How much extra compression can the materials etc handle before life expectancy is reduced in exchange for performance gain.Because I am putting in two extra base gaskets to get the top of piston aligned with the bottom of exhaust port at BDC the compression will not be much different to what I already have. Approx 175PSI give or take a few PSI.
5) I have a 2T but I’m guessing this can increase performance on 4T as well.
Most certainly but 4T usually have fairly high compression ratio to begin with ie 12.5 – 13.5 to one. Their performance gains can be done in many different ways like cams valves timing dome shape etc
Hope this helps
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