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Old 12-22-2007
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1050 one lunger
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Join Date: Sep 2007
Location: pine city mn.
Posts: 5,057
Default old sleds, new fuel

fuel quality over the last 10 years has changed a lot. in a lot of states we now have 10% ethonal. or basically 10%alcohol in the gas. sleds built 10 years ago require 88 octane but back then it had no ethonal. and fuel had a longer storage life. there are a lot of sleds that are running 87 octane fuel and are popping holes in the piston tops.
two things are going on. the newer fuel even though its close to 88 octane has the ethonal in it. alcohol burns at a different rate than standard gas. it also lowers the octane of gas. so the alcohol in the gas is causing enough detonation to pop the hole in the piston.
the other thing going on is that the ethonal is displacing gas, making the fuel leaner than straight gas, now most sleds stock were jetted fat. but the gas in the last couple years has taken all that fat out of jetting. so now even if you have stock jets you are basically jetted for 10+ zero.
you have to either run 92 octane or jet up 1-2 sizes on older sleds to protect themselves. especially if you are going to be adding pipes or aftermarket heads.
we are going through the same thing that the muscle cars went through when lead was taken out of fuel. it used to be that lead could help the valves. but once lead was taken out all of them cars eventually started burning valves. the cure was to buy lead additive for you gas tank all the time, or pay to have hardened seats put in. we are in the same boat now, we have to keep an eye on plugs with older sleds and adjust accordingly.

basically just a heads up to check plugs and run premium on older sleds.
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