Quote:
Originally Posted by CubbyRI
Thanks George! Question, in the case of hi-compression etc you mentioned a flycut groove for a copper ring to set into. is that grooved in the block, the head, or both? How deep is it? Where to source that ring or do u make it and what about the butt ends if so? whats the rest of the gasket? it's not a round groove so how is it cut around the perimeter in that odd shape?
In my case engine is stock compression etc, but there was a deep groove where the fire ring ate into the head especially around the exhaust valve corner. Plus it was pretty warped. I dont know how much I took off but it had to be .010" and prob a little more. How much would this increase compression?
sorry for lotta questions but hey, someone may read this and be souping up their kohler!
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I'm not sure how you o ring a non round head other than to use a CNC mill as I don't modify kohlers, but on 2 strokes it is easier as they are round. Or air cooled ohv engines.
The o rings are usually cut from copper stock.
they would leak if not a solid.
I have milled/flycut Kohler flatheads a max of .040 to increase compression slightly, any more than that and you have to clay the head to see if there is valve interference.
a flow bench is helpful as although going more than 040, might be possible, you are shrouding the valves and while getting more compression/power you might be loosing it with reduced air flow.
at higher rpm's.
I have never gotten into building high horsepower kohler flatheads.
other than to flycut a head to max.040
I do see a quicker response to the throttle with a cut head but never did any dyno results.
Now as far as you surfacing your head with sandpaper,
if you removed .003 I'd be very surprised.
it takes one hell of lot of physical movement to go that far.
I have not CC'd the combustion chamber in a head before and after, it was milling to try to calculate the compression increase on a flathead kohler.
I have done a few SBC chevy's, mostly to balance them to around 62cc's after they were cleaned/milled up by a shop.
Best to ask your questions at one of the pulling sites where the guys are up to date and can tell you off the top of their heads what you gain in Cr. by taking "X" amount off the head and what you have to do to the head to retain flow.
in the Ford flathead days we relieved the blocks to get better flow into the cylinder, then milled the head to restore what we lost from the cylinder relief in the upper edge of the block.
of course there were higher popup pistons and a variety of aftermarker heads for them like Allstate, Fenton, offy, Edelbrock etc. all history long gone.
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