Comfortable top speed

[Bryce Mcclintock]

Hi guys I have a 52 cranbrook standard 3 speed and its original diff unsure of ratio. It has a later 230 engine in it that's been reconditioned and run in just wonder what your thoughts are on what a safe sustained top speed would be in relation to engine revs . Open road speed here in New Zealand is 100 kilometers so about 62 miles and the car gets there not trouble but man it sounds like it's reving hard or is this just the nature of the beast with the 3 speed?  

[Ivan_B]

How does it sound at 70-90?  I would think this to be more appropriate speed. Take the right lane and take your time. That's what I usually do

[keithb7]

My 1938 sedan 3 speed manual with a 25" 237 ci engine, has a 4.11 rear end. I can run it up to 90-100 km/hr. The revs are not likable to my ears, yet It'll do it.  I like how it drives, handles and stops at speeds of 80-85 km/hr.

 

My 1938 coupe with a 25" 251 ci engine, 3 speed manual, has a 3.90 rear end, but it also has overdrive. This one does very well at 100 km/hr. Yet I live in the 85-90 km/hr range. I seem to feel a little safer with the stock skinny tires at 90.  The engine feels very good with this one at higher speeds.

 

Its old, has no crash zones. No seat belts. No real safety features except laminated glass. 100 plus km/hr to me, is not sustainable for reasons beyond engine RPMs.

 

[D35 Torpedo]

My car has 373s and 60 is no problem, 70 is fine. It really starts to sing around 80.

[SteveR]

When I first got my 37 Plymouth with a 230 3 speed 4.11 gears It sounded like it was screaming at 45mph. I have owned this now for 5 years and have gotten used to the engine. I prefer to run her at 45-50mph. I know she will comfortably go faster but the suspension and the lack of any seat belts tell me depression is the better part of Valar.

[Dan Hiebert]

As another Forum member once told me, if you think it's noisy at 60 mph, run it at 70 mph for a while.  When bone stock, these cars are noisy compared to modern cars.  I believe top RPM for performance, such as it is, with these flathead sixes is 3.5K.  I've always been happy not so much with how fast I drive, but how the car runs at between 1.5K and 2K rpms (no overdrive).  I'd think that way, regardless of the rear end ratio, you'll find the sweet spot you like with the car's roadability, which may not be as fast as everyone else.  But, yes, these cars can be noisy by nature.   

[Sniper]

2 hours ago, Dan Hiebert said:

When bone stock, these cars are noisy compared to modern cars.

 

Exactly and the noisiest part is the cooling fan.

 

I drove from Memphis to San Diego in my 64 300, 4.10 gears and a three speed manual.  It sang to me.  But back then the speed limit was 55.  Which I never did, lol.

[Plymouthy Adams]

4 hours ago, SteveR said:

When I first got my 37 Plymouth with a 230 3 speed 4.11 gears It sounded like it was screaming at 45mph. I have owned this now for 5 years and have gotten used to the engine. I prefer to run her at 45-50mph. I know she will comfortably go faster but the suspension and the lack of any seat belts tell me depression is the better part of Valar.

I'd be depressed also running at those lower speeds....

[FarmerJon]

I have a '48 with 217 engine, 3.9 gears. Radial tires.

In theory 3600 rpm (factory redline) is 78 mph. Typically these old engines just stop pulling when they are spinning too fast. They can't eat valves like a OHV can. You just have to worry about rod bearings getting enough oil 

 

It hums along fine 55-65. Brakes are adequate, and suspension seems to hold the road well enough. There is enough power on tap to pull around other motorists.

At 70-75 I can tell that I need to tighten up my old front end, due mostly to vibration. There is power when I need it, but the pedal at cruise isn't far from the floor, and any power needed is a WOT affair.

80-85 is an all hands on deck, pedal to the floor experience. 

Once front end gets freshened up and lightly modified, this may be more comfortable, but as others have mentioned, these old cars offer no safety net, so you better be in a good place with your maker if you crash.

 

Your '52 is likely 3.73 gears, so assuming your suspension and brakes are in good shape, going the speed limit should pose no trouble to your engine. Embrace the sounds of the road, it is normal.

 

ETA: don't forget that the prewar cars are straight axle, parallel leaf front ends. Nothing like the IFS of the post war cars.

Tire selection also makes a difference. 

 

Edited July 30, 2023 by FarmerJon

[TodFitch]

10 hours ago, Bryce Mcclintock said:

Hi guys I have a 52 cranbrook standard 3 speed and its original diff unsure of ratio. It has a later 230 engine in it that's been reconditioned and run in just wonder what your thoughts are on what a safe sustained top speed would be in relation to engine revs . Open road speed here in New Zealand is 100 kilometers so about 62 miles and the car gets there not trouble but man it sounds like it's reving hard or is this just the nature of the beast with the 3 speed?  

 

26 minutes ago, FarmerJon said:

Your '52 is likely 3.73 gears, so assuming your suspension and brakes are in good shape, going the speed limit should pose no trouble to your engine. Embrace the sounds of the road, it is normal.

 

This is the answer.

 

For American cars at least, high revs on the highway was the norm and you definitely heard a roar at speed. Much of that due to the fan, but other things as well.

 

With similar gearing the '63 Plymouth I learned to drive on was quite at home on the then new freeways at 70 MPH and even when they raised the Arizona speed limit to 75 MPH in the pre-55 MPH days. But you really heard the mechanicals. After the 1973 gas fiasco manufacturers started focusing more one fuel economy with taller rear ends and over the years added a lot more sound proofing to the cabin so things got a lot quieter at speed.

 

For what it is worth, I have driven my '33 with its stock 4.375:1 rear end all day at speeds between 60 and 65 MPH. That is 100 KPH for people who live in lands with rational measuring systems. A bit on the fast side for the '33 as its suspension and braking is designed for slower speeds. But by the time your '53 was built the suspension was greatly improved and you have larger brakes, etc. Your '53, in good mechanical condition, should have no issues at your 100 KPH speed limits.

 

Another for what it is worth: My current daily driver is an EV. At highway speeds you hear a bit of tire noise and the faintest hint of wind noise. Even when pulling a fairly steep grade at freeway speeds. The darned thing is practically silent and absolutely no engine vibration. My guess is that drivers who are raised in the coming EV era will worry that they are beating their noisy 2020 vintage internal combustion powered collector car too hard when running it at 60 MPH.

[greg g]

Well, as part of quality control the engine assembly folks would pull random engines, mount them in a water brake dyno and run them under load at 3600 rpm for 24 hours. 3600 is where peak hp was rated by the factory, red line who knows?  My car has 4.11 gears.  With 28.75 diameter tires, 65 indicated on the speedometer  is 62 on GPS.  This calculated to 3280 apx. Rpm.  When I had my engine done, I asked the machinist about sustainable cruising rpms.  He suggested between 75% to 85% of factory hp rpm, depending on general engine condition. So for mine with a recent rebuild, good oil pressure 40 to 45 psi, goodcompression, and 170 degree coolant Temps, I am in that range with a couple hundred rpm in reserve.

 

There are several online calculators where you can plug in your known gear ratio (3rd gear is 1 to 1) and tire diameter and solve for speed or rpm or both.

Edited July 30, 2023 by greg g

[D35 Torpedo]

I've hit 95 once....I wonder what RPM it was turning...best to not think about it.

[Plymouthy Adams]

what was the tailwind speed and down hill grade?   lol  I kid of course.  Many folks would never push one of these old cars for love nor money.  

[Sniper]

95 kmh?

 

95 mph?

 

[Bryan G]

How much massaging was old Lee Petty doing with his Plymouth? I suppose he knew the limits!

[Happy 46R]

I recently installed a tach in my 230 ci 102 hp 46 Dodge coupe. Using a GPS app on my phone I can do 90 KMH at 2750 rpm. At 3000 rpm she touches 105 KMH and this is with a standard 3 spd transmission and no overdrive. Sorry I don't have the gear ratio for you.  Dave

[D35 Torpedo]

9 hours ago, Sniper said:

95 kmh?

 

95 mph?

 

MPH my friend. I felt like Johnny Mantz.

[Matt Wilson]

Over on dodgepowerwagon.com, there is at least one guy who says that when he was using his 3/4-ton WW2 trucks with the 230 engine as his daily drivers, he routinely cruised at 3200 rpm.  He says he put around 250,000 miles on his trucks when they were his primary transportation (I don't think it was a single truck and probably not a single rebuild), but he says he never noticed any ill effects from driving that way.  Mind you, the engine has to be in decent shape and maintenance is important to be doing this, but that can be said for any engine that is being pushed a little. 

 

Just a possible data point for consideration.  I've heard similar stories from other people.  But ultimately, it's up to you and your comfort level.

[Matt Wilson]

Here's an extremely detailed accounting of one original owner's experience with his 1951 DeSoto Suburban.  He talks about driving his car many tens of thousands of miles between engine rebuilds, much of it at 3200rpm, and sounds like he occasionally went beyond that for brief periods, but generally avoided reaching 3600 rpm, his "mental redline."  This car was equipped with a 251 cid engine (which was later converted to a 265), so it's a 25"engine, which some say are more durable in terms of the rod bearings, than the 23" engines, with their offset rods, such as the 230.  Nonetheless, I think it points to what these engines are capable of, if in good shape and well-maintained.

 

This article is a long read, but worth it.

 

https://www.allpar.com/threads/the-1951-desoto-suburban-long-term-owners-report-of-a-truly-noble-motor-car.236556/

Edited July 31, 2023 by Matt Wilson

[Merle Coggins]

I've done a few longer road trips in my truck with sustained RPM's between 3000 and 3500 with no ill effects. I also know the condition of my engine as I built it when I restored the truck. Having a tachometer helps understand the true RPM without the fan noise leading to you believe it's spinning faster than it is. 

Not the greatest picture, but this was on a road trip to Detroit for a WPC meet, traveling down I-94. 

[Matt Wilson]

2 hours ago, Merle Coggins said:

I've done a few longer road trips in my truck with sustained RPM's between 3000 and 3500 with no ill effects. I also know the condition of my engine as I built it when I restored the truck. Having a tachometer helps understand the true RPM without the fan noise leading to you believe it's spinning faster than it is. 

Not the greatest picture, but this was on a road trip to Detroit for a WPC meet, traveling down I-94. 

Hey Merle, mostly just curious, but which engine do you have in your truck?

 

Also, how many miles on your engine since the rebuild?

 

Thanks!

Edited July 31, 2023 by Matt Wilson

[Merle Coggins]

1 hour ago, Matt Wilson said:

Hey Merle, mostly just curious, but which engine do you have in your truck?

 

Also, how many miles on your engine since the rebuild?

 

Thanks!

 

My truck has the 23" block 218 CID engine. Pretty much the same engine that Plymouth used. I don't know exactly how many miles are on it since the rebuild, but I estimate it to be close to 7000.  

[Matt Wilson]

1 hour ago, Merle Coggins said:

 

My truck has the 23" block 218 CID engine. Pretty much the same engine that Plymouth used. I don't know exactly how many miles are on it since the rebuild, but I estimate it to be close to 7000.  

Thanks, Merle.  I like mentally collecting little data points like this, showing that these engines are tougher than people often give them credit for.  When I first bought my Power Wagon, over 30 years ago, I had a lot of people tell me these engines wouldn't tolerate anything over about 2500 rpm for any length of time.  As time went by, I started learning that this doesn't seem to be true.

[Curt Lee]

By and large, the big limiting factor in driving speed "way back when" was actual road condition coupled with embryonic tire technology. I can remember as a child in the mid sixties, my Mom driving Great granddad's 47 Dodge with fluid drive. Now; that car was not all THAT old in, say, 1964, but Mom could manage it and she was a good driver, could run almost anything but not a stick. We lived on a farm, with a long gravel (or mud, depending) driveway, and secondary roads in Virginia even in those days were rough, uncomfortable dirt tracks in some cases. Funny... never saw a four wheel drive until the mid '70's ...... I digress. Given decent roads and tires, and solid maintenance of the vehicle, and I daresay the high side of 70mph would be easy to do. 

I do wholeheartedly support the installation of lap and shoulder belts in any car or truck not so equipped, if you intend to make full use of those 218 cubic inches...

[desoto1939]

On 7/30/2023 at 9:03 AM, FarmerJon said:

I have a '48 with 217 engine, 3.9 gears. Radial tires.

In theory 3600 rpm (factory redline) is 78 mph. Typically these old engines just stop pulling when they are spinning too fast. They can't eat valves like a OHV can. You just have to worry about rod bearings getting enough oil 

 

It hums along fine 55-65. Brakes are adequate, and suspension seems to hold the road well enough. There is enough power on tap to pull around other motorists.

At 70-75 I can tell that I need to tighten up my old front end, due mostly to vibration. There is power when I need it, but the pedal at cruise isn't far from the floor, and any power needed is a WOT affair.

80-85 is an all hands on deck, pedal to the floor experience. 

Once front end gets freshened up and lightly modified, this may be more comfortable, but as others have mentioned, these old cars offer no safety net, so you better be in a good place with your maker if you crash.

 

Your '52 is likely 3.73 gears, so assuming your suspension and brakes are in good shape, going the speed limit should pose no trouble to your engine. Embrace the sounds of the road, it is normal.

 

ETA: don't forget that the prewar cars are straight axle, parallel leaf front ends. Nothing like the IFS of the post war cars.

Tire selection also makes a difference. 

 

My Pre-War 1939 Desoto does not have a straight front axle. It has independent from suspension and this was stock from the factory. I also have coil springs and not leaf springs on the front I have leaf springs on the rear axle. I also run the 600X 16 stock rims with the Goodyear Airtires that are bias ply tires. These are thires that have the ribs on the outside of the tire and were the factory style tire in the late 1930's into the mid 1940;s until they changed over to the 15 inch rim.  My happy speed for my car is around the 50-53 MPH. Last June I traveled from Phila, Pa to Altoona,Pa via the Pa turnpike traveling around 53 mph and got around 16-18 mpg over a trip of 550 miles.  Not bad for a car that is 84 years old technology and still running the original Bal and Ball Carb and 3 speed trans with no overdrive.

 

Rich Hartung