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dezertdoug wrote:
hello I'm deans brother thanks for all the replies.hear is the info we are working with;
bore 86.5 already over1.5mm or.060
stroke 86
head 36 cc's this a SSS head from nissan
deck hgt .018
stk gasket is 1.5mm
dish piston .120 deep 2.710 dia
CR looking for is 7.5-1\8.0-1
STD gasket is only 1.2mm when compressed. With those parts you got about 11:1 comp, just right for naturally aspirated engine. (min volume = chamber + piston dish + gasket - deck height as pistons come over deck height) is about 36cc + 12cc + 5 - 2 = 51cc
Comp ratio is (500+51)/51 = 10.8
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15 psi boost with intercooler max adv of timming of 24 deg.cam is 112 * special turbo grind
How much advance is retarted when on boost? With those comp and boost there should be very little advance in boost, probably under 10 degrees as mixture burns very rapidly at high pressure.
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this melted the edge of the pistons within a short time no other damage was done fuel sytem is a weber progesive 36\42 with 100 octane fuel holley blue fuel pump with
if you more info contact me please we are eager to get this running correct thanks doug
Change that SSS-head to standard A87 closed-chamber which has about 43cc chamber. That itself lowers comp ratio under 10: and chamber should be ported for better flow which also increases volume by few cc. And remember that with high comp ratio and high boost needed ignition advance under boost is minimal, with 24 degree advance engine probably won't detonate but as mixture burns too early pistons can't handle heat.
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