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Author Topic:   Engine Compression
Winland Racing
Dirt Maniac

Total posts: 122
posted September 14, 2005 03:47 PM  
I have a 350 .030 over with .125 pistons just rebuilt. I am running 041 casting 1.94 valves which is a 64cc combustion chamber. Shaved down about 5000th. What will my approximate compression ratio be? What octane gas is recommended?
Am I doing my motor a disservice by installing the 64cc heads or should I go to a 76cc head?

Thanks,
WR#66

J3
Dirt Maniac

Total posts: 188
posted September 14, 2005 03:57 PM  
CR depends on a couple of other factors as well that you didn't mention. Go to the tool box and there is a calculator that figures CR for you.

Keep the 64cc heads, more CR more power.

nine finger
Dirt Forum Racer

Total posts: 76
posted September 15, 2005 04:08 AM  
those 041 are some of my most favorite heads. unless you have a .000 deck height with the steel shim gaskets i doubt you are 10 to 1.

Winland Racing
Dirt Maniac

Total posts: 122
posted September 15, 2005 07:33 PM  
This was input I received from the machine shop manager that I am around 11.5 to 1 with my current set up and that I should either change my heads or run higher octane. I normally run pump gas.
Anyhow, one of the problems I had with this setup was top rpm. I was only able to pull 4800 rpms on a 1/4 track.
491 lift hydraulic cam, cast intake,Qjet, powerglide, 373 rear gears. 670something final gear.
I have 3 races coming up and I want to run with the pack.
WR#66

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Winland Racing
http://www.freewebs.com/winlandenduroracing/

leapinlizard
Dirt Freak

Total posts: 402
posted September 16, 2005 09:31 AM  
You'll need to overify 36' of timing and use race gas. 11.5 will burn down a motor at 93 octane.

mike9
Dirt Full Roller

Total posts: 72
posted September 16, 2005 12:35 PM  
assuming you are at zero deck and you have 5cc valve reliefs and you used the "thick" not shim gaskets this should be 10.2 to 1 compression

Winland Racing
Dirt Maniac

Total posts: 122
posted September 19, 2005 11:37 AM  
What is the octane I should be looking for?

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Winland Racing
http://www.freewebs.com/winlandenduroracing/

mike9
Dirt Full Roller

Total posts: 72
posted September 19, 2005 12:27 PM  
mix 110 octane with prem unleaded 2 to 1 you will be fine that is 2 gallons of prem to 1 gall of 110. that will give you an effective octane of 97.33 which is plenty foer a 10.2 to 1

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