Posted by Jackson Reimund on Monday, November 25, 2002 at 5:04PM :
In Reply to: Installing Chrysler Long Block in 1/2 Ton WC posted by WC-12 Joe on Sunday, November 24, 2002 at 0:52AM :
Hi Joe,
Go for it!!!!!
I know this is a user truck for you. I have been running the 237 in my M-37 for twenty years. These short stroke motors, shortest stroke of the flatheads, are so smooth with more HP and RPM than the 230 and will cruse all day at 55 to 60 mph in the M-37 with 5:83 gears. With your 4:89 55 to 60 will be a delight.
Definition: Flathead; The fewest number of parts traveling the shortest possible distance..
Thinking from there it gets short and sweet.
The Spitfire head 241 is pretty old (1940 last year) and has a stock compression ratio of 6.80 The truck 237 head has a compression ratio of 6.60 no real difference. I don't think the 237 industrial head would be any different than the truck model. A little higher ratio would be good. The later Spitfire motors had a higher ratio. 7.00 for the 250 and 7.50 for the 265 which is pretty high for a long stroke flathead. However on the 237 short stroke a ratio of 7.5 to 8.0 would be perfect. I would not go for any more than 8.0 Perhaps 7.80 would be a good compromise for a user friendly motor.
While four wheeling in low gears the 237 brings in maximum torque at 1200 at 6.60 ratio. This is a lower rpm than the longer stroke motors and a real advantage with a one speed in out transfer case. However when you increase you compression ratio you Max Torque RPM will increase some to 1400 RPM. Small trade off.
Being as you have no appreciable difference with the 241 I would use the 237 head and have it milled. You can tell the difference in ratio when you flip the heads over and look at the width of the combustion chambers across side to side. The wider the chamber the lower the compression ratio and the narrower the higher the ratio. When you mill the head it will shrink down. You can eyeball the ratio with a little practice.
The 237 truck manifold runs a very nice 4 bolt 3 and 1/2 inch center dump exhaust pipe. This is a real manifold compared to the restricted 218/230 types. You can do some real tuning of your air flow with these manifolds. This is the area where you have some real options with carburetor/plentum and exhaust/muffler to get performance from a flathead. Better and cheaper set up than dual intake and dual exhaust for the user friendly flatheads.
Use a 5 blade fan and large fan pulley. I use a 6 3/4 inch fan pulley in my M-37 Most all of your disconcerting noise and vibration at highway speeds is the fan flying away much to fast. You will pull plenty enough air to never over heat and cut the noise, wear and tear and lost energy. You will run along whisper quiet.
Next step while you are at it is use the flywheel from the industrial engine and go to the 11 inch clutch. The industrial and truck engines that used the long block had the holes in the flywheel drilled for the 10 and 11 inch clutches. You wont believe how much smoother the 11" is. It takes less leg power to depress and hold and will last a life time. Your truck will love it!
Not sure but the cam from an industrial motor may not be the one you want to use. Industrial motors are dialed in to run all day at one RPM and the cam grind would be set up for that RPM constant. My guess is that the spitfire, Industrial, and truck would be ground different for the application and perhaps stroke/duration as well. I don't think that the high performance cams for sale would be necessarily right ether as these would be dialed in for the long stroke 265 type motors. Someone here on the forum may have that data in shop manuals that I don't have. If anyone has that info please post it here or send it to me via email please.
Pretty simple huh? You got to love it.
Jackson