Driving a 39 Plymouth on the interstate?

[Guest cjbpaquin]

I'm thinking about buying a '39 plymouth....i've been looking for a nice 39 Chrylser 8 but have not been able to find the right one....now I have opportunity on the '39 Plymouth conv.

My question is: what's it really like driving the '39 with the 4.11 rear end ( i think that's right) on the interstate...can it sustain 55 mph for an hour and a half or so? Or is the comfortable cruising speed more like 45-50? I've heard different things...some say 60 mph all day long...big difference between 45 and 60....60 you're slow, 45 you're a hazard...any feedback or personal experience much appreciated.

[ply33]

If, and its a big if, the drivetrain is in reasonably good condition you can cruise at 60 to 65 in that car. I limit my long distance driving in my '33 with its stock 4.375:1 rear end to just above 60 to keep the RPMs below 3300 or so. Longest single day I've done in recent years at that speed has been about 450 miles.

It will sound quite different than a modern car at those speeds with engine turning over so much faster and you'll find lots of people looking for different rear ends and/or over drive transmissions. But the car will run just fine at 60 or 65. Go much faster than that, or if you are into following too close, you'll want to address the brakes.

[NTX5467]

From the tire diameter I found on Coker's website, a 6.00-16 tire with a 4.11 axle ratio would yield about 20mph/1000 rpm in high gear. That would make 3000rpm the approx rpm at 60mph. Power peak is about 600 rpm higher. Even though this is a long-stroke engine.

Personally, I don't see why it wouldn't run at 60mph all day long as that was one of the faster speed limits when the car was designed and built. Many roads, though, were more like 45-50mph roads, either by design or condition.

To me, other than having good oil pressure when at operating temperature, good ignition, and a good fuel pump, I'd be MORE concerned with how "clean" the radiator was internally AND how clean the block's water passages might be. Keeping it oiled is one thing, but keeping the water flowing and removing heat (as it should) can be very important in any kind of extended highway driving. AND don't forget about the condition of the various chassis parts . . . like front suspension bushings, rear spring eye-bushings and shackle bushings, shock absorbers, brakes. Having a capable and willing engine can be quickly marginalized by other subsystems which might need attention.

In my very younger years, we had a '51 Plymouth that would run 70mph. We replaced it with a '56 Plymouth Savoy sedan. It'd run on the highway just fine, too. Both were flathead 6s. And our '51 GMC 1/2ton pickup would easily run 60 all day long, even 70 sometimes, with the 228 6 in it.

Just some thoughts,

NTX5467