I'm totally new to the M37 & variants, so I pose a question:
Does this motor have a civilian equivalent, and did that motor have forced induction parts available 'back in the day'?
I'm asking because I have a '48 Willys CJ2A that came with an original-style L134 Willys Go-Devil 4 cyl flathead. Back in the early '50s McCollough (spelling?) that made a two-speed belt-driven supercharger for the L134. In 'Low' it developed 2.5psi of boost and in 'High' it developed 5psi. McCollough eventually became Paxton, who everyone knows and loves (hates?).
I'm working on adapting a modern turbo to fulfill this role for my flatty, but last April I toasted the motor. Low boost pressure blew the rings on the #4 cylinder. Taking it to 4000 rpm (the L134's redline) hit about 12 pounds of boost and nuked the rings on rear cylinder. I'm not done with this yet. I will make this work, one way or another.
Given the M37 motor's penchant for tossing rods at high RPM I would be very careful with forced induction. If you decide to do it, I would highly recommend picking up a 'test motor' and build (in military terms) a 'ground-hop' kit - a frame to mount the motor to with gauges, radiator, etc so you can start and run a motor without it being in the vehicle.
However you go about it, it will need to be a low-boost system. Flatheads, by design, are prone to developing hot spots along the top edge of the cylinder wall closest to the valves, especially at compression ratios greater than 8:1 or so, causing pre-detoation. This depends a bit on the motor itself though. Basically, your forced induction system probably shouldn't push the motor past a 9:1 or so compression ratio.
I've had a lot of "well, why bother then?" feedback on my plans, but I'm pushing forward anyway. I don't want a 9:1 equivalent, I want forced induction. A carbureted, naturally aspirated engine at a 9:1 compression ratio will still have mixture and power issues as altitude increases. A 7:1 compression motor running a mild turbo tuned to 2400 feet (where we live) will still develop good power at 11,000 feet while a 9:1 N/A motor will fall off as altitude increases. It will also have an easier time running with traffic locally. Coincidentally, it'll also sound really freakin' cool.
I would also SERIOUSLY consider an aftermarket ignition where you can limit engine RPMs to prevent over-revving the motor.
To put my plans in perspective, I bought my Willys looking for a daily driver/hunting/camping rig. I had initially ruled jeeps out because they're just too small for a family of four with a black lab. I was looking for a Scout, or a Jeep Commando, or something, and tripped across a 1948 CJ2A that had been stretched 24" right behind the front seats. Other details aside, my build plan is this: If Willys had built an expedition truck on the CJ platform in 1948, this is what they would have done. I'm calling it the 'Atacama edition' jeep.
I want to be able to hunt locally, but have the option to head south and go up into the mountains in central Idaho where roads can hit 11,000 feet. I want to be able to haul my gear in with my wife, bag and elk or two, and get back out in the harshest of conditions.
I already know that the Willys can handle three feet of snow with open diffs and chains on the back. With chains only on the front, I pulled a '74 International pickup with a slide-in camper and frozen brakes through bumper-deep snow.
My plans for my M43 are to make it the 'base-camp' rig with the jeep taking us closer to the hunting areas. If I had an unlimited budget, I'd drop the motor completely and go propane-electric. Replace the motor with a 15KW propane generator, electric motor, and enough battery to run 5-10 miles on mountain logging roads. Charge up the batts and roll into the hunting area with only the noise of the tires creeping along at 1-2 mph.
I didn't mean to hijack the thread, so I'll shut up
Les
