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compression ratio

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Brian101MH

New User
This is for the tractor pullers out there. At 2800 RPM"s flat head 6, what compression ratio should i shoot for this winter during our rebuild ? Right now we are at about 6:1 . I understand the higher the compression ratio the more power, but at some point I"m sure its to much at that RPM limit.
thanks in advance for the help, Brian
 
8.5 to 9.0 will run pretty good on pump fuel. If you have access to aviation gas then 14 to 1 but have a lot of extra arts available
Walt
 
It's a flathead, valve in block or L head, high compression is not what they're famous for because you have all that additional area over the valves, shave to much off the head and you don't have room for the valves to open or the fuel to flow in and exhaust out. I'm guessing you have a Massey Harris I'm thinking Continental engine. I've seen propane forklifts with six cylinder Continental engines they might have pistons and heads that will help you on the compression if they were built as a propane engines or you might see what the car applications were using for compression (Checker and Kaiser) come to mind. I don't think you'll have compression/RPM issues, heck in the 60's some street cars were running 13.9:1 and they still behaved at lower RPMs, heck my old Pontiac had the high compression and it only ran about 2200 rpms at 70MPH.
 
One tip you want to remember is to have a seperate switch for you ignition coil. With high compression engines you want to get them cranking first then turn the ignition on. They start easier.
 
Thats a new one had hi comp engines in the past and didnt need a seperate sw how hi comp are you talking about over 10-12.
 
The Kiser-Frazer and I think same as used in several tractors for a 226.2 cu in engine was 7.3 compression rated at 3650 rpm.
 
We also had 105 octane fuel that you can't get unless you have access to aviation fuel.
91 octane 8.5 is about the limit.
Walt
 
I"m thinking 10 or 12 but not sure. The valves are in the block, I dont want to mill head and hurt the lift. Thinking either a hi comp piston or filling the head (compression chamber) to raise the ratio.
 
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