Happy speed

[JIPJOBXX]

I was just wondering at what speed on our old mopars do you think they run the best without over revving? As for mine it seems to about 45 mph as the engine doesn't seem to be working hard to hold that speed. But this would make sence as the average speed for early forties was about 45 mph. I would like to know what latter flat head six's do as far as happy speeds. My old Dodge produces about 100 hp and that about it.

[Norm's Coupe]

I've only had my 48 up to about 55 or 60 MPH. Seems to handle that speed well.

[TodFitch]

When actually trying to get somewhere in a timely manner I drive my stock 1933 with its 4.375:1 rear end at 60 MPH. I actually worry more about the brakes and handling than the engine at that speed.

With you "newer" L-6 and a 4.11:1 rear end you should be able to cruise at 65 or so.

For the full story:

http://www.ply33.com/Misc/speed

[greg g]

do one of the calculators that figure tire diameter, gears and speed. The factory rated HP at 3600 RPM if you cruise at 80 to 85% of that you should be good all day. With my set up 62 is 2980 rpm.

[JIPJOBXX]

I guess what I need is temporary tach to check out the rpms at certain speeds.

[TodFitch]

I guess what I need is temporary tach to check out the rpms at certain speeds.

Unless your clutch is slipping it is a simple matter of your rear end ratio and your tire diameter. Most tires nowadays have a listing for the mounted tire diameter and your rear end ratio ought to be stamped on the differential pinion carrier.

There are a bunch of on-line calculators out there that can take that information and show you the speed for any given RPM. Mine is at http://www.ply33.com/Misc/speed#calc

The defaults on it are for my car (17 inch tires and 4.375:1 rear end) but you can easily put in your own data.

[Oldguy48]

In the mid-60's, I attended a community college about 60 miles away from home. Came home most every weekend in a P15. The car seemed to be very content running 55-60 MPH, and did so for 2 years. And I used that P15 to tow a 60 Impala Convertible I dragged home from the town I was attending college at. No problem except a snapped tow cable when I was nearly home.

[BobT-47P15]

Around 55-ish for mine.

Has a slightly lower geared differential from a 39 Dodge, but doesn't

make a huge difference.

[moose]

My '55 with 3.73 gears and a peppy '51 218, seems pretty content at 70. I do have smaller diameter radials on it though, and it reads about 10 higher than my actual speed, so I'm still getting passed by everybody.

[Plymouthy Adams]

my 54 with the 3.73 gears and the 230 is very content at 70 with plenty of accelertion available..car rides very quiet and the engine does not sound super busy so to speak but I never hooked a tach to see the actual rpm...course I have not put the seats back in yet either...still doing some house work..

[55 Fargo]

my 54 with the 3.73 gears and the 230 is very content at 70 with plenty of accelertion available..car rides very quiet and the engine does not sound super busy so to speak but I never hooked a tach to see the actual rpm...course I have not put the seats back in yet either...still doing some house work..

Tim I have the same basic set-up, but at 60 mph, which is reading about 65 mph on the speedo, she sounds busy.

I have close to factory sized tires, P205-75-15 tires, about 27 inches.

2 things in my case, no inerior except seats and carpets + more noise, so may sound busier.

My engine has miles on her, but does have decent compression, about 100psi average across the board, good oli pressure, 40 psi at an idele, and 50 to 55 at 50 MPH.

But I am still afraid to push her too hard, plus my car is a 47 Chrylser Coupe, probably weighs about 700 more lbs than a P15 coupe........Fred

[Plymouthy Adams]

I still have the tall tires that are stock on these cars..when I go to modern radials..that may change the way my car sounds, rides and handles. The 54 is so well undercoated beneath and with the sound dampening material on the inner compartment..I am sure this adds greatly to the quiet this car seems to have. I will say this...the front end even with new shocks still seems to "float" as these cars were designed to do...this was a period of smooth ride..performance was not in the equation per say. Mom and pops were the buyers..not youths with rocket powered brainwaves.. I keep putting of the install of interior...yeah..other more pressing things to do...but back on the road I am sure the subject of relocted shocks will be addressed along with the eventful upgrade to discs...right now..she still be a stocker...

[Merle Coggins]

I must say that a good interior and exhaust system makes a big difference. My truck seems comfortable at 50 - 55 but will get right up to 65 - 70 without complaint. I have 3.73 gears, thanks to Normspeed, and 235/75R-15 tires. Before installing my interior and upgrading the exhaust system it sounded downright angry above 60, but now it sounds much better.

Merle

[RobertKB]

For me, in any of my flatties, any speed is a happy speed. I just love driving them.

[Don Coatney]

I shipped my car to Paris and made this run. You can hear me slapping all 5 gears in my five speed transmission. I did run a few red lights along the way but heck what is life in the fast lane (140 mph at one point) all about?

Follow this link.

http://www.youtube.com/watch?v=VqHrCLt3Geo

[blueskies]

Overdrive....

My '50 with overdrive will cruise happily all day long at 70 to 75 mph... It turns 2500 rpms at 70 mph.

Pete

[blueskies]

...and made this run...

I've seen that film short maybe 25 times, and love it every time... thanks for reminding me to watch it again.

Pete

[old woolie]

For me, in any of my flatties, any speed is a happy speed. I just love driving them.

Me too.

[Captain Neon]

My P15 is most comfortable at 50 to 55 mph.