hey whats a good compression to run in the woods. lets hear what some of you guys run.

hehe anything above 10 you gonna need some race fuel least i think. a lot of people stick around 9-9.5 for pumper gas. mine is 12.98:1

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2332cc Air Cooled Screaming Meanie. Predator Singleseat.

"Lets go get stupid"

Comp = cheep HP

14.78/1

somebody correct me if im wrong but high compression helps bottom end torque but hurts topend horsepower and vice versa with low compression
not 100% sure about that just what i was thinking

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Just Stand On It!!!!

Chris

i'd hate to see a plug blow out of that thing with that kinda compression you could kill somebody with it.lol but serious what octane fuel do you have to run with that much compression?chad

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NOW GAS IT!!!!!

I have heavy 4 seater trail buggy so I set mine at 8.5/1 for low end chuggin' and engine life longevity and to be able to run pump gas

is it better to run shims under the cylinders or copper gaskets under the heads to lower the compression

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Just Stand On It!!!!

Chris

I had to run both because my heads had been cut down for higher comp. but if you can get enough clearance with just one of them I would go with the copper head gasket . its a easier job and helps seal the jug to the head ...JMO

I run about 13:1 in mine. Kyle's right, anything much more than 10:1 will need to run on racing fuel. At least blended racing fuel with 93 octane pump gas.

-Dakotah/koko

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-Dakotah/koko
keep on keepin' on!!

I thought about what I said about having to run both head gaskets and barrel shims and it was confusing
I could have ran all barrel shims but I wanted to have a head gasket for its sealing ability so I had to use both to get my deck hight where it needed to be

The way you guys saw my motor ran at Wellsville, that is 9.5:1 compression with top-secret fuel

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"Loud pipes saves lives"

surely somebody can answer this
and if so what is a happy medium and is there anyway to check like with a compression gauge without tearing down the motor
i would really like to now what size i needed so that i can get them and pushrods beforhand and put it right back together with as little down time as possible

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Just Stand On It!!!!

Chris

High compression is overrated. Its fine up untill you run out of race fuel. You can not just stop at the local station and fill up. Personally i would keep compression down (8 or 9:1) were you can run pump gas. Your motor will last longer and be less expensive to run. Gas is only down in price right now. It will continue to climb. The last time I bought race fuel it was 7 Bucks a gallon. There really is not that much power to gain for the price to be paid. A good set of ported heads will yield you way more HP and Torque than raising compression. Invest the money were it really counts.

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Water cooled Dry Sumped Subaru Powered Turbo Charged Fuel Injected 2500CC Tank. Oh Rah! He who dies with the most Toys not only wins, He also wears them out!

Because of Cam overlap checking with a compression gauge will only tell you the static. You would really need to pull the heads and CC them and find the deck hieght to really know.

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Water cooled Dry Sumped Subaru Powered Turbo Charged Fuel Injected 2500CC Tank. Oh Rah! He who dies with the most Toys not only wins, He also wears them out!

Yep thats the ONLY way to really know. I had never CC'd a head before and Greg showed me how you do it with water pretty neat ol trick. Then dial indicator for deck height.

Here is a cool calculator you can figure it out with after you find all the numbers.

http://www.aircooled.net/gnrlsite/resou ... /calcs.htm

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2332cc Air Cooled Screaming Meanie. Predator Singleseat.

"Lets go get stupid"

thanks guysfor the info
i was afraid id have to pull it apart though just wanted to be sure before i and sidnt have too

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Just Stand On It!!!!

Chris

I ran around 12:1 on my 2500cc and mixed the fuel half and half that way i could still afford to ride lol..

116. no mix. Just bought 10 drums.

You have to match your fuel with your comp. I can lug mine in 3rd gear in the woods down to 500 to 700 rpm with no problem.
I know a lot of guys that have low comp. motors but still run race gas. That can hurt your motor as much as high comp. with pump gas.

never heard of to much octane so to speak huerting anything but i knew too little would
i talked to the guy that built my engine the other day and he said best he remembered itwas either 10 or 10.5 to1
so what gas mix or octane would be best or should i lower it with copper head gaskets and if so how much for running pump gas??????

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Just Stand On It!!!!

Chris

http://www.renegadepro1.com/racing_fuels.html This web site should help.

low compresion is for luggin motors,thats how mine is built,100 thosands deck height,high compression means higher rpm

You will gain HP across the the rpm range with compression. But detonation is what you
have to be careful of. In the heat of summer with less than 60% it will start to detonate
quicker. Lower RPM than a day that's 70 and 90%. I run race fuel only on 12.5+ motors.
On motors 10.5 to 12.5 I run 60/40 pump gas/alky and drop the heat range on the plugs.
10.5 and lower gets pump gas. Good stuff in the heat. cheep in the cool. Race gas in the
winter takes too long for the oil to get hot enough to burn the water/fuel out of it.
Race gas in an 8.5 motor will hurt HP, due to combustion and egt too low to make power.
You just have to find the sweet spot for your combo.
JMO

Octane number ratings are the fuels resistance to detonation.
Higher number fuels light off harder than lower octane fuels.
That's why race gas is used in high compression engines.
It won't light till the plug fires.
Using race gas in an engine that doesn't need it wastes money and actually runs poor compared to pump gas.
Run only as much octane as you need to eliminate detonation......no matter how good it smells burning.....

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Gary

Turbo VW Sand Racer
Polaris Ranger



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