Originally posted by apostate
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Digger and I have been conversing about these engines for a decade, it's only natural for two people who approach things scientifically to come to the similar conclusions.
Exactly have many m20's have you built? I'm sure I could look at shop records and site a number.
BTW Just went and measured the "0" punched in the block. Difficult to measure so I pressed a piece of tin solder in it and came up with just over ~.010 (2.5mm). So, an extra shave is not going to be the death of the OP's block - specially if he was to take the max .010 and take the rest off the head. I rather leave the heads as full height as possible, though, since shaving it removes the quench band.
Originally posted by SLEEPYDUB
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As far as quench, with a boosted engine, it is more important than N/A as it reduces hot spots and potential detonation. To get a good quench, square and deck the block, bore it, replace the intermediate shaft bearings (be cautions and make sure your machinist understands the procedure). Then you will fit your pistons/crank/rods. Finally you will want to use a sacrificial head gasket (only thing VR gasket is good for lol) and torque it down with used bolts, but before mounting it, place a pieces of solder on the angle part of the piston. Some people like to use clay, but I find the solder is easier to measure (not a bad idea to also do the piston to valve clearance at this time). If the solder is more than .037" by a good margin, shave the head to match.
For pistons, just use the factory style with the raised wrist pin to compensate for the longer rods, and factory dome, you won't need anything special. Many piston MFGR's already have the files to avoid a custom piston fee.
Did you have a MFGR in mind already?
EDIT: Missed the part about compression. Go with as much as your tuner feels comfortable with, but I haven't had an issue going as high as 10:1. Local here has an e39 m5 with stock compression (never opened, 11:1), and is making 780whp @1bar with only meth for charge cooling (no FMIC).
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