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Old September 16th, 2008, 10:45 AM   #1
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Default 12.5:1 compression - what octane?

Anyone know what octane I should be running?
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Old September 16th, 2008, 10:50 AM   #2
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I'd start with premium and if it knocks, move up to some 105

or go propane
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Old September 16th, 2008, 11:00 AM   #3
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93 with correct timing.

I seriously doubt you want to run race fuel all the time, but I might be wrong.
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Old September 16th, 2008, 11:03 AM   #4
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Most Likely 110 Its What I Have To Run But Mine Is Litel Higher Comp. Which Is Or Close To $6 Gal.
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Old September 16th, 2008, 11:06 AM   #5
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Aluminum heads? Iron heads? What kind of cam? Dymanic compression?
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Old September 16th, 2008, 11:11 AM   #6
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Aluminum heads? Iron heads? What kind of cam? Dymanic compression?
Factory AMC iron heads, which should be 58cc on her motor. It would have cost me more if they were 291's, so I doubt they are.
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Old September 16th, 2008, 11:13 AM   #7
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I'd start with premium and if it knocks, move up to some 105

or go propane
x2

propane has a 104 octane rating
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Old September 16th, 2008, 11:41 AM   #8
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Ethanol, rejet carb.
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Old September 16th, 2008, 11:42 AM   #9
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is that your actual CR (measured), or a guess on what you should have? what ever made you want to run 12.5:1?
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Old September 16th, 2008, 11:47 AM   #10
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is that your actual CR (measured), or a guess on what you should have? what ever made you want to run 12.5:1?
Just talked to her about this on the phone. The motor should be late-70's, so that number may be high. She's going to verify the head casting and then look up the amounts of material removed from the heads & block, as well as try to get some specs on the pistons. The pistons *may* have been rated for 52cc heads in their description, so she may not be quite as high as 12.5:1.
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Old September 16th, 2008, 11:56 AM   #11
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Anything over 10 seems to run poopy on 93. In my experiance anyway, lets face it checking timing ever or even every other time you hit the trail is a huge PIA. I do it on my race motor all the time,and I hate it.
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Old September 16th, 2008, 12:03 PM   #12
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http://www.qrckarts.com/store/index..../313/index.cfm

Check bottom of page.
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Old September 16th, 2008, 12:22 PM   #13
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Someone get a real good deal on a motor or something? Not really an all around motor for wheeling by the sounds of it so far.
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Old September 16th, 2008, 12:52 PM   #14
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Remember you need to take into account the head gasket thickness.

Convert to run E85, problem sovled.
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Old September 16th, 2008, 12:55 PM   #15
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Someone get a real good deal on a motor or something? Not really an all around motor for wheeling by the sounds of it so far.
It was stock when she got it.
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Old September 16th, 2008, 01:00 PM   #16
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It was stock when she got it.
So, what is the intended purpose of this Jeep? (I dont feel like reading the 100 page thread to get caught up). Last time I saw it... it was purple or something and getting torn apart. I think I helped get it to her parents house or something with Bill.
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Old September 16th, 2008, 01:12 PM   #17
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So, what is the intended purpose of this Jeep? (I dont feel like reading the 100 page thread to get caught up). Last time I saw it... it was purple or something and getting torn apart. I think I helped get it to her parents house or something with Bill.
Its going to be a daily driver.
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Old September 16th, 2008, 01:23 PM   #18
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Quote:
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x2

propane has a 104 octane rating


X3


Although usually propane is deemed to have up to 110 octane. And cheaper than gas by about a dollar
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Old September 16th, 2008, 01:23 PM   #19
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I can hardly get away with running 93. If i'm really heavy into the gas it has some spark knock. I can't afford to DD that thing.

I hope you have a ton of money linz to feed the best!

E85 is 110....
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Old September 16th, 2008, 01:32 PM   #20
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Its going to be a daily driver.
Who the hell talked her into this one?
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