Driving our old cars at high speeds

[Chuck51631]

When our cars were built the speed limit was about 45 mph. I now live in Florida where the speed limit on the interstate is 70 mph. Most drive faster than that. I have had my car up to 60 mph. It wants to go faster but at 60 the motor sounds like it is ready to come thru the hood.

I always maintain the engine, use 30w oil. I have radial tires on the car and the front suspension has been rebuilt. Would it be safe to drive distances at high speeds? Will I do damage to the engine?

I am missing out on going to alot of car shows since they are not in my area.

Any feedback is appriciated.

Thank You in advance for taking the time to reply.

Chuck

[55 Fargo]

Okay yes, very good question you are asking.

What rear gearing do yall have, if 3.90 or 4.11, you are gonna rev, and in the Florida summer humid heat things are gonna get warm, quick, especially on a freeway doing 60 mph plus.

Options, install mopar 81/4 diff with 3.23 gears, install R10 OD trans, convert to 5 speed trans, with OD.

The tallest tires on the rear, can help a bit, bring down RPMs down  few hunnert.

Things to consider, ensure engine is up to the task, they don't like sustained high rpm, and super hot temps, espcially if old and tired. I would keep a tired engine below 2500 rpm, which translates to 55-60 mph, not 65-70 mph.

Please provide more info, your diff gear ratio, rear tire size, and state of your engine.....

[ggdad1951]

it all comes down to RPM.  Long distance at too high of an RPM will not do well for these old beasts.  Use the calculator to see what you end up with speed at RPM.

 

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

[TodFitch]

When our cars were built the speed limit was about 45 mph. . .

 

Maybe for some eastern states it was that low. But by 1941 there were plenty of states with posted limits of 60 MPH. During WW2 a 35 MPH national speed limit was enforced to conserve tires and fuel but that went away when the war ended.

 

If your P15 era car can't cruise at 60 MPH in stock configuration then something is wrong with it. Trucks were geared for slower speed running, so there could well be an issue running them that fast in stock configuration, but not for cars.

[Chuck51631]

My car is all orignal, engine, transmission and rear differential are the one's Plymouth installed when the car was built. I can tell you I am in third gear by 25 mph. The engine is strong, does not burn any oil. I usually change the oil every 500- 1000 miles. It is usually clean when I drain it. I feel better safe than sorry. I do not drive the car much during the summer. too hot and no air conditioning. I will start out early take my time and keep the speed at 55-60 mph. I never had this problem up north, speed limits are still 55 mph. 

[55 Fargo]

1 other issue, is braking, and steering, you better have excellent braking and steering doing 60 mph plus on a loaded freeway, seat belts would not be a bad idea either.

Tod F mentioned a P15, should cruise at 60 mph, provided the engine is in good internal condition, cooling system, oiling etc. Engines with high mileage, and/or tired, your risk, and the higher the rpm, the hotter the engine temp= possibility for problems.

You are in FLA, Charlie lives near Orlndo, and has front disc conversion kits for you car, might be a good idea...

[P15-D24]

I drive my at 65 all day long, have done so for many years. Your use to hearing modern cars with overdrives that cruise as a lower rpm.  

[greg g]

My 46 has a 4.1 to 1 rear end.  When I first purchased the car it was stock from the factory.  We made the trip from Penn State U to central NY about 240 miles, several times.  This was basically all interstate highway which was marked for 65 mph.  Currently the car has a rebuilt 56 230 engine, with the stock trans and rear end.  I am running 225 75 15 tires on the rear.  Using an on line calculator into which you enter your gear ratios, (1to 1 for trans) and tire diameter, it figures out to 3200 rpms at 60 MPH.  The factory used to pull engines from the assembly line, put them on a dyno, load them up with some resistance, and run them at 3600 rpm (the peak HP rpm) for 50 hours.  So if you assume 3600 rpms is about 65 MPH, they put 3250 miles on the engine at that rate, non stop.  So a 3 hour highway trip is a walk in the park by comparison.  So find a calculator, run you numbers and see where your rpms are for a given over the road speed, check your speedo against a gps unit if you like. Then if you are near 80% of 3600 rpm for your cruise speed you are good to go for any distance you choose.  You mention no smoke and no loss of oil, but the critical item is engine temp, how does your run?   My set up has taken me from central NY to Vermont, Charlotte NC, the DC area, Maryland, PA, Mass, Detroit, and other distant points.  The only failure I have experienced was a thrown Fan belt.  

 

On a personal note I can not understand the  need to change your oil at 500 miles.  Even without an oil filter the factory recommendation was at least 1000 miles, and that was back when roads were dirt, the air was full of coal and diesel particulates, and oil was basically oil without the additives and petrochemical know how, and leaded gas.  What are you doing with your drained oil???  Can you send it to me????  I will get some life out if it.  I put 2 to 3 thousand miles per year on my car and change the oil at the beginning of the driving season.

 

To add to the comment above, probably 80 % of the engine oise you hear at speed is coming from the fan.

Edited February 1, 2013 by greg g

[1941Rick]

If you want to drive this car anywhere anytime I would suggest finding a R10 O/D, a set of 3:91 rear gears and convert to electronic ignition.

As for brakes, aside from being a single master cylinder they are more than efficient to stop the car.

Just remember..........speed kills.........in more then one way

[Don Coatney]

If you want to drive this car anywhere anytime I would suggest finding a R10 O/D, a set of 3:91 rear gears and convert to electronic ignition.

As for brakes, aside from being a single master cylinder they are more than efficient to stop the car.

Just remember..........speed kills.........in more then one way

 

Why an electronic ignition? I drive my car anywhere, anytime without an electronic ignition.

[TodFitch]

Why an electronic ignition? I drive my car anywhere, anytime without an electronic ignition.

 

If it fails on the road with a 6v+ ground electronic ignition you can have the car towed to the destination as the parts will have to be shipped to you from the manufacturer. So you get to ride in the cab of the tow truck and enjoy the rest of your trip with someone else driving.

 

But if you have the old points and condenser system you are obliged to buy new parts at any decent nearby auto supply, fix it by the side of the road and then continue driving to your destination. That is just such a hassle.

 

Kidding aside, I find that points based ignition systems are cheap, reliable, easy to diagnose problems when they happen and easy to fix. What's not to like about that?

 

Just checked with NAPA online and for my ZIP code here's the complete list for my car:

Rotor: $19.60

Points: $16.00

Condenser: $12.00

Cap: $13.60

 

So worst comes to worst, you are out a bit over $60 and half a day. At least half a day is all it take for my "local better auto supply" to get all those parts into the store. And the most failure prone part, the points, are small enough that if you feel insecure you can carry and extra set or two so no need to even go to a store.

 

I can get a spare original distributor for about $50. Cleaned up and rebuilt we're talking about $110 with new rotor, cap, etc. So I can have a complete spare distributor for about the cost of a Pertronix unit.

 

But in all the years I've driven points and condensor ignition based cars I've never had a failure on the road. They generally degrade slowly as the points wear and you can schedule things to do you tune up/repairs in the comfort of your own garage or driveway before they become an issue on the road.

[Uncle-Pekka]

I've been running mostly 55mph march speed. My rear end ratio is 1:4.1. Once I tried to push it to 70mph... as the needle was very near to 70 mark, the engine suddenly backfired with an enormous blast under the hood. I instantly let up the throttle, fearing that I just blew off the entire carburetor. Then couple of misfires more, splatter and speed decresed to 40 mph. I pulled off and vent to check under the hood. No damage after all, I started the engine and drove rest of the leg easy 50 mph...

 

Now late in autumn I found a R10 out of '53 Savoy, which I intend to install coming summer. Still missing relay and solenoid, keep looking for decent prices deals. I am confident this car has undercarriage good for 70...80 mph driving, thus look forward to get the OD functional.

[Don Coatney]

To add to what Tod said, If you are running a dual point setup (such as I am) should I have a point failure on the road I can simply dis-able the faulty set of points and continue driving on the good set.

[Merle Coggins]

I'm with Don and Tod on the electronic ignition issue too. And as Tod pointed out, the parts are cheap enough. The last time I got tune-up parts for my truck I got double of everything "just to have spares handy if needed". Then I just decided to package them in a small container and store them under the seat of my truck. It doesn't take up much room. Even though I don't ever expect to have a failure of this simple ignition system while on the road I know the spare parts are handy if it happens.

 

I also agree that most of the noise you are hearing is from the fan. No fancy clutch fans on these rigs to quiet things down.

 

Merle

Edited February 2, 2013 by Merle Coggins

[TodFitch]

I've been running mostly 55mph march speed. My rear end ratio is 1:4.1. Once I tried to push it to 70mph... as the needle was very near to 70 mark, the engine suddenly backfired with an enormous blast under the hood. . .

My rear end ratio is 1:4.375 and I once tried to put it to 70 MPH. Actually, I was pushing it to see what it would do on a flat section of freeway with a posted speed of 70 MPH. And I just barely achieved 70 MPH, as measured by a GPS, before the road started up a grade. Not too bad for the 190 cu. in. engine pushing a car with the aerodynamics of a barn door down the road.

 

Biggest thing I noticed was that my passenger stopped talking and started staring at the speedometer and acting a little uncomfortable.

 

Comfortable cruising speed with that 4.375 to 1 rear end ratio is between 55 and 60 though I do push it to 65 for some distances if I'm on a freeway. The suspension wasn't designed speeds much over 60 that and the tiny brakes are a concern. Mostly back roads at 45 to 50 are the fun way to go.

[Don Coatney]

I have a 255CI engine, 3.55/1 differential, and a 27% reduction overdrive. I once did close to 100 MPH in my car. I still had more to go but I thought it was not a good idea to do so on a highway. I have driven well over 600 miles in one day on the interstate crusing at 70 MPH. With my gearing setup my engine is only spinning about 2200 RPM's at this speed.

 

I have an electric pusher fan on a thermostat controller and no belt driven engine cooling fan. I have the thermostat set to start the fan at about 180 degrees. At any speed above 30 MPH the electric fan does not run even on the hottest summer days so fan noise is not an issue for me.

 

 

 

[frankieflathead]

I've had my stock '49 D24 up to 65 m.p.h., but the engine seems much happier at 55. I also agree with C38Spitfire6 about the brakes on these cars. Even if they're working at 100% (which mine are), I have to seriously wonder about fade resistance and overall stopping distance in an emergency stop from 75 or 80. My general rule of thumb : Try not to drive on any roads built after the car was, and observe the speed limits on them.

 

[55 Fargo]

Yup, and why not keep spare parts on the glove box, like I also do, an ignition coil resistor. I have not had points juts up and fail in any car, had wrong or points out of spec etc  leading to hard start, poor running, but not down right failure. A lot of my beater cars as a youth all had points.

I also know some who have converted to electronic and are happy about it, I would try a slant 6 electronic ignition conversion, those parts should be readily available in many parts store.

If it fails on the road with a 6v+ ground electronic ignition you can have the car towed to the destination as the parts will have to be shipped to you from the manufacturer. So you get to ride in the cab of the tow truck and enjoy the rest of your trip with someone else driving.

 

But if you have the old points and condenser system you are obliged to buy new parts at any decent nearby auto supply, fix it by the side of the road and then continue driving to your destination. That is just such a hassle.

 

Kidding aside, I find that points based ignition systems are cheap, reliable, easy to diagnose problems when they happen and easy to fix. What's not to like about that?

 

Just checked with NAPA online and for my ZIP code here's the complete list for my car:

Rotor: $19.60

Points: $16.00

Condenser: $12.00

Cap: $13.60

 

So worst comes to worst, you are out a bit over $60 and half a day. At least half a day is all it take for my "local better auto supply" to get all those parts into the store. And the most failure prone part, the points, are small enough that if you feel insecure you can carry and extra set or two so no need to even go to a store.

 

I can get a spare original distributor for about $50. Cleaned up and rebuilt we're talking about $110 with new rotor, cap, etc. So I can have a complete spare distributor for about the cost of a Pertronix unit.

 

But in all the years I've driven points and condenser ignition based cars I've never had a failure on the road. They generally degrade slowly as the points wear and you can schedule things to do you tune up/repairs in the comfort of your own garage or driveway before they become an issue on the road.

 

Hey Unc, stoppin is the problem at the higher speeds, hope your binders are in good shape, hey yall have accurate speedos by chance.....LOL

I've been running mostly 55mph march speed. My rear end ratio is 1:4.1. Once I tried to push it to 70mph... as the needle was very near to 70 mark, the engine suddenly backfired with an enormous blast under the hood. I instantly let up the throttle, fearing that I just blew off the entire carburetor. Then couple of misfires more, splatter and speed decresed to 40 mph. I pulled off and vent to check under the hood. No damage after all, I started the engine and drove rest of the leg easy 50 mph...

 

Now late in autumn I found a R10 out of '53 Savoy, which I intend to install coming summer. Still missing relay and solenoid, keep looking for decent prices deals. I am confident this car has undercarriage good for 70...80 mph driving, thus look forward to get the OD functional.

[55 Fargo]

I have a 255CI engine, 3.55/1 differential, and a 27% reduction overdrive. I once did close to 100 MPH in my car. I still had more to go but I thought it was not a good idea to do so on a highway. I have driven well over 600 miles in one day on the interstate crusing at 70 MPH. With my gearing setup my engine is only spinning about 2200 RPM's at this speed.

 

I have an electric pusher fan on a thermostat controller and no belt driven engine cooling fan. I have the thermostat set to start the fan at about 180 degrees. At any speed above 30 MPH the electric fan does not run even on the hottest summer days so fan noise is not an issue for me.

 

 

 

Your car is well equipped Don, rebuilt big block, dual carbs/exhaust, dual point diz, front disc brakes, dual mc. So why not cruise at 70 mph, but the poster has a stock P15, and the stock brakes, he may best at 60mph and lower, until He does the upgrades you have. I know others have rebuilt engines, and drive there cars at high RPM, but on an older engine, might be better off to either do what you have done, or take it easy....

[greg g]

My traveling kit contains a spare distributor all set up with good used points condenser and rotor.  If I have a distributor related failure, it's a 10 minute job to swap out the units and be on my way.  Also carry a spare coil.  Haven't touched them in 8 years except to verify that are still there. 

[austinsailor]

Speed limit of 45? Until the 50's there were no speed limits many places. The real limiter was the highway. Speed limits became common as the roads improved.

In Missouri I think the set statewide speed limits in '55, maybe '56.

When I crossed Nevada in Nov of 65 there was no limit. There was open range. I came across a guy who'd topped a hill at 100+ and met a herd of cows. What a mess. We gave him a ride to the next town.

[55 Fargo]

Okay here is what I did, fired up ole 55 Fargo truck 251, 4 spd, 3.23 diff, mileage unknown.

It is 10 below outside, engine ran excellent with used points, used plug wires, used coil, used resistor, new spark plugs  new rotor and cap, condenser is used. 

Drove for 7 miles, froze butt off, actually my feet, heater works fine, but no cab insulation on floor or ceiling, some open voids. Drove down frozen gravel roads at 50 mph, thought of you Guys, especially those down south, had a moment of clarity, and drove home as the sun is going down, and it ain't no fun if this baby dies at 10 below and getting colder for tonight.

These really are great little engines, love how they sound and run....

[1941Rick]

When it comes to any upgrades its whatever floats your boat. Myself I went to electronic Mopar ignition for the dependability and the much hotter spark. It is a set it and forget it. There is a reason the car manufactuers went this way. No moving parts to wear out. Dont have the ever wearing rub block to keep adjusting.  Spare parts in my car consist of a fan belt. Thats it. My car is set up similar to Don's. Only difference is the ignition the rear ratio  (3:91), and a 218 engine. Very dependable and relaxing to drive......I am always getting the "you drove that car where"? comment.

[55 Fargo]

When it comes to any upgrades its whatever floats your boat. Myself I went to electronic Mopar ignition for the dependability and the much hotter spark. It is a set it and forget it. There is a reason the car manufactuers went this way. No moving parts to wear out. Dont have the ever wearing rub block to keep adjusting.  Spare parts in my car consist of a fan belt. Thats it. My car is set up similar to Don's. Only difference is the ignition the rear ratio  (3:91), and a 218 engine. Very dependable and relaxing to drive......I am always getting the "you drove that car where"? comment.

Gotta love it, set-up for modern day cruising, good on yah.....

[1941Rick]

When it comes to any upgrade it is whatever floats your boat. I went to the slant 6 electonic for the much hotter spark, no radio interference. and no points to wear out. But that is me. The car manufacuers went this way for a reason..I can cruise all day long at highway speeds and the engine does not skip a beat. ( did before ). My spare parts kit consists of only a fan belt. The car is set up very much like Dons except for engine size and rear ratio, and will go where ever she is pointed. Hot August Nights in Reno this summer (2013)