I've pretty much decided to go with a flathead in my 26 T coupe. One of the things that was holding me back was the lack of horsepower as compared to even a mild modern V8. However I think the cool factor is just to big to pass up. In my research I find that the stock compression ratio of flatheads is very low, even compared to smog motor standards, being less than 7 to 1 in most cases. Now when building modern muscle car motors I've always found increasing the compression ratio was cheap horsepower (up to the point you could get good enough gas). Now for the actual stupid question: Wouldn't bumping the compression ratio up in the neighborhood of 9-9.5 to 1 create a nice bump in horsepower and still be compatible with today's gas? Would this require special beefing up of the bottom end, or is there something about flatheads in this area I don't understand? Thanks, Scott
Shit if you are thinking of a T which is light weight, just put a huffer on that 6.5-7 to 1 flathead and have about 180 HP and enough torque to really move that T.....
On any engine developement project you add power until something breaks then reinforce the broken bits and add more power. The cycle continues until you run out of money or get satisfied. The lower end of a stock Flathead is weak compared to any modern engine and the three main crank with long strokes need very careful balancing. I would go easy on the HP end of things and stick with around 150-175HP and make it pretty. It won't take much to move that coupe and the sound of the engine will make you happy.
Yeah, I'm not looking for a fire breathing 8 sec machine, just enough to haze the tires now and again. It just seemed that compared to other motors that the compression ratio on flatheads seemed ridiculously low. I understand back in the teens and early twentys a low compression ratio was required because they were running on basically Colman lantern fuel (white gas) Thanks, Scott
You can raise it to the 9:1 compression range naturaly aspirated and not have major problems. Compression ratios didn't start comming up until the '50s and even some mid '50s valve in head engines were still running in the 8:1 compression range. I may lean toward an 8:1 compression ratio if it were me and remember that you are hazing skinny tires on a light car. That and don't try to drive it like it is a high winding 283, if you keep your revs within a normal operating range for a flatty it is not as likely to come apart on you.
Pork, Am I correct in understanding the top end of the rev-o-meter for your Mark 1 Mod 0 hot rod flathead is about 4500? Scott
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