Rpm 201 flathead 6

[Joshuanotsosmart17]

I have a 1939 Plymouth P7 deluxe business coupe with the 201 flathead6 three speed manual trans on the floor stock rear end, with dual stromberg super 97 carbs, my question is are theses engines a high reving engine because I take it on the highway all the time at 55-70 mph and it seems like it’s screaming but maybe that’s just me this is my first classic car I just don’t kno much about the flathead 6 any info on how to tell to much rpm’s would be great, there is. No rpm gauge in the car . She runs great and just hit 59k miles on it. 

[TodFitch]

If, and it is a pretty big if, the drivetrain is in good condition your '39 should be able to cruise at 60 or 65 MPH. It will be very noisy compared to a modern car with a lot of that roar being fan noise. See: https://www.ply33.com/Misc/speed

[greg g]

The guy who rebuiltmy 56 230 sited what he called rhe 80% rule.  This was what he defined as being found long stroke engines, those of 4 1/2 inch and more.  This states that sustained cruising rpm that is near 80% of factory peak horsepower rpm is OK.  So if you go to an online gearing calculator,  put in your tire overall diameter, your final drive ratio, and check for rpm, you can get close to 80% of 3600, you are good to go.  

 

My car has 4:11 rear-end, 27.75 diameter  tires.  The calculator puts that at 3300 rpm, which is 65 indicated, 62 on gps. Operating temp is170, oil pressure is 42 psi.  At that speed, I can drive all day, but I am more concerned with brakes and idiots than I am about wind noise, fan noise and tire noise.  Your experience may vary...

 

We have taken several 500 mile plus road trips over the years with no mechanical issues except for a broken fan belt.

 

Chrysler engineers used to pull random engines from the assembly line, hook them to a waterbrake dyno and run them at 4000 rpm for 24 hours against a load as quality control process.  So you can  judge for yourself what strain you want to go up against.   I have often wondered  what happened to those dynoed engines, did they get retruned to be rebuilt, or did they go back to the assembly  line?  Conventional wisdom seems to indicate that operation above 3600, leads to expensive noises from the engine lower rotating parts.  The oiling route is cam centric rather than main and rod bearing centric.

 

You may be the exception, but most would recommend against steady state 70 mph operation.  Keep us posted.