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« on: May 23, 2014, 10:43:34 pm »
I built a 31avs engine last year. Eng had stock avs piston, arc billet rod, precision cam, billet fly wheel, crank was balanced and welded, billet timing gear, ec dominator carb, and head was shaved .130, pushrods cut to length, and ec roller rockers, compression was 190 lbs on warm eng, ( was checked with 2 different gauges(new)), I never did check timing, just lined up with second notch. Eng ran great last year, always keep exhaust temp around 1200 F. Always ran Sunoco 110 race fuel, took it out this year ran great for three races then out of know were exploded the piston at 5900 rpm doing severe damage to most components. The only thing I did different was mixed my 110 fuel with 93 octane fuel with a 50/50 mix. So just built new 31 eng, stk piston arc rod, ec billet cam, billet flywheel, 28cu billet crank (with bushing in pan), ec dominator carb, head shaved .100, chrome molly pushrods to length, ec roller rockers. Set timing to 30 degrees, (degree wheel and timing light) checked compression after a little running and was 195 lbs. I know my figures are off some but im figuring that's about 13:1 comp ratio. My question is did my old eng explode because I mixed the fuel 110 and 93 (lowered octane)or was there another problem that I had. While inspecting my old eng for evidence I also found that if you rubbed your fingers around the cylinder wall in felt like a wash board (rippled) all the way around the cylinder and the full length of travel of the piston. Should I continue to run Sunoco 110 straight or should I mix it 50/50 with 93 octane. Any ideas on the rippled cylinder wall, guessing that didn't happen all at once. Any suggestions or comments welcome Thank you