Posted by Matt Wilson on Friday, November 17, 2000 at 22:05:02:
In Reply to: Max Speed of a C-3-PW posted by David Pratt on Friday, November 17, 2000 at 21:13:50:
David,
I bought a data plate from Vintage Power Wagons, and it says top speed in 4th gear, transfer case in high range, is 52 mph. However, the people at Vintage Power Wagons and other owners are usually quick to indicate that 45 mph is really a more practical top speed. My engine has a governor between the carburetor and the intake manifold. Yours should have this as well, if it's not been removed. On my truck the governor limits the engine speed to 3200 rpm, and it's probably the same for yours. At this engine speed, the road speed for a truck with 5.83 gears and the standard 9 X 16 tires (which have a rolling radius of about 17") would be 55 mph. But again, this is not recommended for long engine life. And of course, at that speed, safety becomes a little more of an issue in this kind of truck with the braking, suspension and steering designed so in the 1940's.
I don't know if 3200 rpm is the redline or not, but I've heard that a rule of thumb that truckers used to use is that you should not cruise for extended periods at engine speeds more than 80% of redline. If we adhere to this thought and assume 3200 is redline, then we would cruise at no more than 2560 rpm. This gives us a road speed of 43 mph for your truck. The home page for this web site has technical specs for a '55 PW, and these specs call out a max horsepower occurring at 3600 rpm, but the governed speed is still 3200 rpm. So I'm not sure about the 3200 redline.
Just so you know, getting 4.89's will allow you to cruise at 53 mph at 2650 rpm. I have 4.89's in my truck, and even with that setup, then engine sounds like it's getting wound up pretty good.
Also, a word of caution: be aware that the engine can be forced to exceed the 3200 rpm governed speed if you go down steep enough hills in gear. The governor merely limits the amount of throttle input from the driver.
Hope this helps.
Matt