Redline/Maximum Continuous Operating RPM - Packard 6 Cylinder Engines

Posted by Ragtime Kid On 2016/2/23 0:37:11

As a former airline pilot, I admit to being particularly obsessive with measurements, indicators, readings, etc.

So, it bugs me not to be able to directly measure the engine RPM and, worse still, to not have any sense of "how much is too much". In aviation, we have green (normal) operating ranges, yellow (a range in which operations are time limited), and a red line (never exceed).

What would those values correspond to on the 245cu in Packard 6 cylinder engine?

The owner's manual references a power output of 100BHP at 3600rpm....so, is that the "redline"?

I have worked out the following speed/RPM relationship using my 4.3:1 final rear end ratio and a tire radius of 13.875" (measured as the tire sits under the weight of the car, thus slightly compressed) with the transmission in high gear:

45MPH @ 2344RPM
50MPH @ 2600RPM
55MPH @ 2864RPM
60MPH @ 3125RPM
69MPH @ 3600RPM (redline?)

From my experience driving the car,the engine noise increases significantly around 55MPH and, while I do have more throttle available on a level stretch, it just "feels" like I'm pushing it to go beyond that. So, does 2800-2900RPM sound to you guys like a reasonable maximum for continuous driving or am I being too conservative?

It would be great to have some real numbers relating to this flathead engine where I could know what the practical limits are.

Any input is much appreciated!