Posted by gtk on Thursday, May 15, 2003 at 8:26PM :
In Reply to: RPM verses MPH in a stock Power Wagon? posted by Willy-N on Thursday, May 15, 2003 at 1:00PM :
Some reference info and personal experiences: This topic has come up on both my P15-D24 and Pilothouse boards. FYI the same flatheads are used in those vehicles in either a 218 or 230 configuration. Tod Fitch who runs the www.ply33.com site has researched this topic and found some relevant info. He also provides the sources. "Over speeding" (aka over revving) an engine is defined as exceeding the RPM that maximum BHP is generated. Most mopar flatheads rate max BHP at 3600 rpm. That puts your "redline" in the 3,500- 3,600 rpm range. Note all Chrysler (mopar) engines were tested at max BHP in 50 hour tests so if you bump that upper level for short periods of time you should be fine. Also noted "for long engine life, max rpm should be held a couple hundred rpm's below max rated brake HP. Also note most governors are set for at least 3200 rpm. Point being, if the engine is in good mechanical condition, you should be able to run 2800 to 3200 all day long. I have driven a P15 (218 ci) cross country on the interstates running 60-65. This was with a 4.1 rear end. RPM was probably around 2900- 3000 based on the small tire size. This was the original engine. I drive my 2wd B1 (4.1 rear) at 2800-3100 all the time (60-65 mph) and that is with the original and very tired engine. Never had a problem. If they needed to run under 2500 rpm the governors would be set to that speed. RE the cranks being soft, I would think the bearing inserts would go a long time before the crank journals. Seems to me you can scratch one of the inserts with your fingernail if you press hard. The coating is very thin. The engineering references are listed on Tod's site if you you want to do more reading. http://www.ply33.com/Misc/speed.html
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