Re: Redline/Maximum Continuous Operating RPM - Packard 6 Cylinder Engines

Posted by DrewLA On 2016/2/23 7:16:27

Your gut is probably going to be your best source of guidance here. If you're looking to maximize the life of your engine, staying at or below the speed at which it feels like you're pushing it is the best course of action. Truthfully, that's all anyone really had to go on back when the cars were new, and given how long your car has been in service, any number of things could have lowered or raised the safe operating range. Anecdotally, I can say it's been my experience that almost any of these cars from the mid-30's onward will comfortably maintain 50 MPH all day long.

And, in fact, there are probably other practical limits that come into play as well around that speed. Consider the bias ply tires, the limit of your brakes, your fuel consumption, the ability to maintain steering control, the capacity of the cooling system, and your tolerance for noise.

A few points of anecdotal reference:

-When we took a 1936 Standard 8 Phaeton to Pasadena for the Rose Parade, we drove it on the freeway and just cruised along at 50 most of the way. For me, 55 felt like I was pushing it just a bit (especially after a guy cut me off), but 50 felt comfortable. More than that and the steering also got a little scary. Different tire size but a similar final drive ratio to the six you reference.

-We had a 1940 120 sedan on the PAC All-Western Regions tour last year. 60-65 was no problem, but 70 felt like a stretch to that driver.

-A properly tuned Model A Ford will run at 45 MPH all day long, and at that speed your distance and time are only limited by your capacity to tolerate noise, vibration, and harshness. Faster and the engine temp will start to climb.