Packard Forum Index » Pre-War (1899-1942)

This may be a question previously asked and if so, apologies, but I have searched and cannot come up with any definitive specs. My question: is there any published info regarding RPM redline on the 245 six? Or does anyone have an educated guess? My estimate would be 5K but even that may be too high. I do know that many on the site warn of driving these motors past their 'usable' power range and I cetainly agree, but would really like to know more about what the revs actually are at highway driving speed and where the 'too-much' line is. Thanks in advance for any info or informed opinions.
Chris.

I don't now an actual number as I've never seen it published (that doesn't mean it hasn't been) but I used to drive my 1940 110 without overdrive at highway speeds all the time with 65 MPH being an average. Visiting my grandparents where my 1941 Henney-Packard was located took at least an hour on the highway each way but no strain on the car at all.

Hi Don,
Thanks for weighing in. I know you have said numerous times that you drove your six at 65-70 MPH all the time with no issues or apparent damage to the engine. I wonder what kind of rear end your car had? You also say you could spin the tires from a stop so it couldn't have been geared that high. I feel like I have a pretty good ear for listening to an mill rev and with my car, 50 seems like the 'no-load' range, 55, she's working and 60, it's 'starting to scream'. Many others on the site have stated that 50-55 is about all you should push these cars to and based on the sound(s) of what I hear, I tend to agree. I just thought if I could get a documented redline and put a tach on the engine, it would give me a more technical baseline, than just 'by ear. Chris.

Peak HP is at 3200 RPM so I wouldn't go past that...

packardinfo.com/xoops/html/downloads/1939_DataBook.pdf

Chris, it had the stock rear end. If it had overdrive (which I later added but never drove it again after the addition) I would have also put in the proper rear end for OD which would have given even better off-the-line performance.

You need to determine what your rear axle ratio is, and determine the diameter of the tires you are using. Knowing that, you can calculate the engine RPM at 60 MPH. Or, you can refer to the literature section on this site and look up the specifications for your particular car and engine, and then measure the tire diameter. You can also check your speedometer / odometer accuracy against a satellite device. Tire diameter varies a lot, and it is critical to calculating engine RPM at road speeds. I found that my speedometer was dead on at 50 MPH, and very close at any speed from about 30 to 65 MPH. Odometer is likewise accurate. A late 1930s Packard engine in good condition can run at 2800 to 3100 RPM for extended periods. Horsepower demand to push a 1940 110 or 120 Packard sedan at 60 MPH on level ground is probably about 30 horsepower. The 6 cylinder engines are just as rugged as the 8 cylinders, maybe more so, but the 6 cylinder cars may have a lower speed axle and a slightly lower RPM horsepower peak. "Red line" is typically horsepower peak + 20% or so. All this assumes the engine and cooling system are in good order and the engine is properly tuned. A proper 6.50 X 16 tire for a pre-war Packard will have a diameter of 29.0 to 30.5" when mounted and inflated. A 7.00 x 16 tire will be around 29.5 to 31.5" diameter. Firestone tires are full diameter, which makes them a good choice for pre-war cars.

Thanks Guys,
All good info and if the peak horsepower is at 3200, redline should be about 3850. That makes sense to me. I have the Coker radial 6.50 X 16's on the car and I believe they are 29" OD. My engine doesn't have that many miles on it since rebuild so it may still be a little 'tight'. It turns over easier now than when I first got it back. I'd have to go back and check but guess there is between 2 & 3000 miles on the new engine. I'm thinking of getting a tach and would probably just hook it up to 'learn' the engine and then remove it as I like the stock look of the plain dash. In the meantime, I did buy one of those digital doo-dads that Kev mentioned in another post where a reflective piece of tape is adhered to the harmonic balance and then you 'shoot' it with the ensor and it gives you RPM. I bought it to synchronize the upper and lower tachs on the diesel on my boat and will bring it home next trip and see what I can find out on the 245. Will post findings then. In the meantime I'll stick to the good old ear; if it sounds too high, it probably is!!! Thanks again for the kmow-how. Smart bunch, you all are! Chris.