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10-10-2007
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 Compression and Race Gas It sounds like Dr. Q is tha man for the Zilla, but I am in more of a hurry for my Zilla back. So needless to say Trinity has my Head and Cylinder, to do the porting. After Talking to them (I really am quite a rookie at these things) I will be running 108 octane race gas. I have gone out and bought the Craftsman Compression tester (see thread below) and checked my compression on my LT250, it is about 153. At what point do you wanna run race gas and what octane VS 91 octane premium pump gas? Is there a formula of head compression VS Octane? Any help for this Rookie would be greatly appreciated. BUSH      |
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10-10-2007
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| i always use race in anything over 160 just to be safe |
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10-11-2007
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| What do you mean "just to be safe" If my compression is high enough, and I dont run race gas....will that blow my engine? |
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10-11-2007
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| Yes it will blow your engine because of predination, but i have heard that anything under 180 is alright. But the factory head is all screwed up so your are should send that in and get it fixed but i haven't found anybody to do it that sounds like they know whats going on. So if you can afford it race gas is cheap insurance to blowing your motor. |
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10-12-2007
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| What is a good range of PSI that your engine should be at? What is a high mark vs what PSI should I do a rebuild? BUSH |
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10-24-2007
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| That all depends on your baseline compression at time of break in
__________________ 86 Honda 310R Power Valve Paul Turner Eliminator pipe 39mm Sudco racing carb 215psi 110 octane 310esr p/v Ported by Neil at C-Leigh Racing +4 Durablue axle +2 Burgard A-arms 87 Quadzilla Lonestar custom swingarm Lonestar axecaliber axle Lonestar steering stem Powder coated frame Custom Paint 42.5mm mikuni Alky carb (soon to be 48mm Packard Lectron) Marvin Shaw suspension LOTS OF CHROME Trinity Drag port ( I know its Trinity, but do you want to race it ?) CPI oof drag pipe am I forgetting anything? hmmmm   Never argue with an idiot. They'll just drag you down to their level, and beat you with experience! |
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10-24-2007
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| compression will vary with porting you need to know the UCCR ( uncorrected compression ratio ) a drag port motor will have less compression kicking it over but will need more octane because the motor has better VE (volumetric efficiency) IMO compression gage is useless depending on the gage and length of the hose it will vary example static compression on a stock motor with 178 deg of ex duration at sea level with 11:1 compression is around 150psi a drag ported motor with 198 deg of duration and 13:1 compression will be right at 150 psi |
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10-24-2007
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| I just did a full rebuild on my zilla and I got 180psi with only 5 kicks. Would have probably gone a bit higher if I had the energy to kick any more. This is with a Dr. Q RX's head and piston. |
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