Driving our old cars at high speeds

[55 Fargo]

You just give her James, glad you can keep pace with modern traffic, that 3.55 diff, will make a big difference too, for rpm.

The factory rated them at 3600 sustained rpm, supposedly for twenty four hours at a time.  I have a Dakota 3.55:1rear end in my 48 P-15 with an engine I assembled myself in 2007 and a friend and I took it on a 4800 mile trip to the west coast and back at speeds of 60 mph to 75mph on interstate 10 in west Texas which has an eighty mile per hour speed limit.  I routinely drive mine 70 mph every where I go on the highways in central Texas just to stay out of the way of the semis, so far no problems in 25000 miles of driving.  I do run radials and disc brakes on the car.

 

Right on Adam, you see a lot of the Furd and Chebby crowds, have to use modern engines, those stovebolt 6s and flathead V8s, can't handle the abuse our old mopar 6s can.....LOL Hey listen, it was the Mopar L head 6, that was used in all kinds of industrial,agriculture,marine applications, anybody ever wonder why.

Not that many years ago, in Winnipeg, there were 2 huge engine reman places, there staple house items were Chrysler flatheadf 6s, my 2 Uncles hauled in many a core to these places..

I also did a rear axle swap to 3.25.  I travel with my father and his (mine too) friends to some NSRA events around the state.  These guys are all "streetrodders" with modern drivetrains so they travel at the posted limit or above.  They do tolerate my 2nd gear hill pulls but I get my share of crap from them about it.  Part of the character of my vehicle is dealing with it's shortcommings.  I sometimes feel that gets lost when everything is fuel injected and air conditioned.  I still get the " you drove that Flathead from......." comments and it still makes me smile when I say yup.  Disc brakes are comming though.  I did notice how much better the vehicle stopped when the 8" Rear axle went in with modern rear brakes.

 

Adam

[55 Fargo]

Just got off the phone with 1 large engine rebuilder, machinist has been there since 1970, they are still building engines, and even have a mopar 251 going on now. At 1 time, before 1990, they would keep 15-20 rebuilt Mopar L head 6s on the floor at all times. They were rebuilding up 20 engines daily in there prime. The other plant Prairie Reman, operated until early 90s, they were the "Chrysler Method' builders, and their house staple was the L head 6 too.

he also told me about 12 years ago, that sadly they threw out many mopar flathead parts, including a 55 gal drum, full of water tubes, they did not think they would be of any demand, and many other parts were sold for wholesale or scrap.

This plant was founded, and is still owned by distant relatives of my Mother, infact my mother's 2 brothers use to haul cores to this place on a regular basis.....

[Plymouthy Adams]

not sure if this will or will not help folks here...good guide line for RPM and ratio and tire...I say not sure because of the very low rpm the flattie max torque is situated and I don't know how flat it remains/drops off as the HP increases with RPM but still a good guideline..just expect higher RPMs and less fuel economy as the base RPM increases...

[55 Fargo]

Nice chart, based on 55 mph, with my present diff gears and 27 inch tires, 55 mph is around 2200 rpm, nice and easy on engine at at that speed...