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Bruce Lancaster · 08-03-2010, 09:38 AM

Well, 267 is still half a litre down from where people start saying "Hey, that's a big flathead!"
It's only a little bigger than a Merc on its third rebuild.
On the compression...you have comp ratio, and you have actual comp pressure.
If the size of the engine actually allows it to fill cylinders well, pressure will be higher than if it is gasping for air and there is less in there to squeeze. Remember cylinder filling and max comp pressure are at torque peak, and as engine revs past that peak to power peak filling is dropping away. It would be interesting to know what the torque curve looks like on a highly developed 6200 RPM small engine versus a big one pulling 296 through there.
Flatdog's 12 second '34 coupe, which I got to drive on a long roadtrip, was shifted no higher than 5200...4-71 blown 307.
Torque curve did not actually curve as far as I could tell...it was monstrously high at all road speeds.

08-03-2010, 09:38 AM	#91
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: Boring a flathead Well, 267 is still half a litre down from where people start saying "Hey, that's a big flathead!" It's only a little bigger than a Merc on its third rebuild. On the compression...you have comp ratio, and you have actual comp pressure. If the size of the engine actually allows it to fill cylinders well, pressure will be higher than if it is gasping for air and there is less in there to squeeze. Remember cylinder filling and max comp pressure are at torque peak, and as engine revs past that peak to power peak filling is dropping away. It would be interesting to know what the torque curve looks like on a highly developed 6200 RPM small engine versus a big one pulling 296 through there. Flatdog's 12 second '34 coupe, which I got to drive on a long roadtrip, was shifted no higher than 5200...4-71 blown 307. Torque curve did not actually curve as far as I could tell...it was monstrously high at all road speeds.