motorway speed with flathead

[Oliver Betker]

Hello,
last week I had a trip from Germany to Denmark with my Cadillac 61 from 1946 with the 348 flathead engine.
While I drove several 100km at a very hot summer day I asked myselve, what speed do everyone other take on a motorway. The normal weekly rides take normaly place in the area arround my home through the landscape, where the speed is slow and cosy.
With the high octan-fuel create the engine a lot of heat, which the coolant system quite good managed. But the temperature at the pistons will be very high I prosume.
Do you have any recomondations, expieriences, because you have longer distances from one place to the other?
Which speed do you normaly use for long distances?
regards from Germany

[Bill Ingler #7799]

Hi Oliver: During my Air Force days I had many long trips to Frankfort and Rammstein Germany. On my days off, I toured your beautiful country and drove many miles on the autobahns. I thought we drove fast in the US until I saw the speeds on your autobahns. In the past 30 plus years of touring the US with my 41 or 47 Cadillac, using our interstate roads for longer trips, I limit the top speed to 55-60 mph. The more traffic the slower speed to around 45mph. My cars will go much faster than 60 but it is the brakes ,that  limit my speed, depending on road traffic. Back when these cars were built, ours roads were designed for 40-45 mph and brakes on new Cadillacs were OK for those speeds. In warmer summer weather and I am cruising 55-60 mph, my temp gauge sometimes will be 2 needle widths to the right of center. That does not bother me as when I rebuilt the engine, the block was cleaned by a metal cleaning company, radiator was re-cored and I run a 5 bladed fan. Have fun with your 47 an by the way, I never found a German beer that I did not like,  Bill     

[C Gorgas]

I limit my speeds to 55-60 mph. I know the car/motor can handle higher speeds but I respect the age of the car. My car has the economy rear end and as such when my speedometer reads 55 mph I am doing 60  Chet

[Jim Miller]

I travel at 55 on the highway in my '41. She will easily do 65, but as pointed out - respecting the age and braking limits I stay slower. The temp gauge has a new sending unit and has never read greater than the far edge of the D in cold. My infrared thermometer will read 195 tops on the heads.

[Brett Baird]

On my drive to the 2009 Grand National in my '41 (950 miles round trip), I tried to keep it around 55 - 60 mph, but found myself doing 65 once in a while.  For the 2016 Grand National I had decided that 65 mph was fast enough for a 75 year old car, but I found myself creeping up to 70 mph or so on occasion.  I generally travel at the speed limit on the interstates - up to 70 mph, and  I do keep a wide berth between myself and the cars ahead of me.  One of the most charming things about these cars is the effortless way they travel on the highway.

[39LaSalleDriver]

As others have noted, I am most comfortable pushing my 39 no further than the 55-60 mph zone. I have for short bursts pushed it up to 65-70 mph and it could handle it for no more than I did, but I don't like putting that much strain on an 80 year old engine. For that matter, I don't like contemplating what could go wrong should I need to lock the brakes down in an emergency at that speed. I tend to spend most of my time in the slow lane watching the world pass me by and leaving plenty of room in front of me to stop should I need to.

So far, I have been pretty fortunate and most people seem to leave me a wide berth. My guess is they figure my car is worth far more than it really is and don't want to take a chance

Sometimes though you get an idiot who just has to cut suddenly into the space I leave myself. Those are real pucker moments. 

[Cadillac Jack 82]

When I had my 37 Lasalle I kept it at 60 MPH.  It wouldnt overheat but I was worried about the wear and tear.

[Oliver Betker]

Many thanks for your replies.
I see that I am not so far away from your tastes of speed.
The comfortable speed for such cars are indeed 50-55ml on landroads. Mostly I try to avoid motorways, because like already mentioned the speed is very high in Germany and with 50mph you are slower than the lorries.
So I drove most of the time 60mph, sometime 65mph to overtake a convoy of trucks at the Autobahn.
But to my shame I have to say, I had additionally a very little caravan at my towbar. Very little, only 250kg, a weight what you could put in your trunk, but the windload is not to underestimate.
I think it was a little to much, but the engine and the coolant system worked fine and I could stay away from the trucks.
But my fuel comsumption rose from 7,9gal/100ml on a cosy Sunday ride up to 9,8gal/100ml on the high speed and load at the Autobahn. (which is 12,6ml/Gallon up to 10,22ml/Gallon, if I calculated it right with your measuring system).
Could anybody confirm these fuel needs with your experiences?

In the forum was the topic 5 bladed fan several times bespoken.
Did you mount an original fan from a model 75 or did you use  aftermarket parts? One tread has a link to an amazon offer with 6 blades. Could that fit?
For the constantly rising summerheat it could be useful to have more airstream through the radiator.
Regards Oliver

[Oliver Betker]

here a Foto from the Little caravan

[39LaSalleDriver]

I tend to get 6-7 miles per gallon at slower speeds (say 25-40 mph) around town with stop and go traffic (lights, stop signs and so forth). Out on the highway and at highway speeds, that number consistently jumps up to right at 11 miles per gallon. That is without towing anything or having any passengers.

[harry s]

Oliver, That is a great looking car and trailer combo. I'm sure you get a lot of attention when driving.  A big part of your fuel consumption is the trailer so I wouldn't worry about it. Just enjoy!      Harry

[Bill Ingler #7799]

Hi Oliver: I used an original 5 bladed fan from a 75 series. My 47 came with a engine pan that was fitted under the radiator as shown in attached picture. The purpose of the pan is to direct  the air that flows through the radiator, back across the engine to help in cooling the engine. Without the pan,  air coming through the radiator will flow down and under the engine.     Bill

[Marty Michaels]

Hello,when I ride the thruway between buffalo and rochesterNYI like to keep between 55 and 60,however I get caught up doing traffic speed.One time doing this I looked down and the speed read 1oo wow.I knew that could not be right so out comes the GPS and find I was doing 84 still to fast for this old timer. Marty..

[The Tassie Devil(le)]

Hello,when I ride the thruway between buffalo and rochesterNYI like to keep between 55 and 60,however I get caught up doing traffic speed.One time doing this I looked down and the speed read 1oo wow.I knew that could not be right so out comes the GPS and find I was doing 84 still to fast for this old timer. Marty.. 

Reminds me of the old days when people would brag that their car would do 100 MPH and even more.   They would swear that their speedo was correct.

It wasn't till things like the GPS revealed that they were way off with their stories.

Bruce.

[Glen]

Reminds me of the old days when people would brag that their car would do 100 MPH and even more.   They would swear that their speedo was correct.

It wasn't till things like the GPS revealed that they were way off with their stories.

Bruce.

Back in the day there were measured miles where you could check your speedometer.  You kind of had to know where it was as it was not real obvious.  Drive through it at a set speed and time yourself with a stopwatch.  Do the math. 
</ ramble mode off > 

[bcroe]

Brakes, tires, and handling will limit top safe speed. 

Hardly anyone takes the trouble to calibrate their gauges, so
there is a lot of error (to what Detroit thinks of as the safe side). 

Mile markers are good if you average a lot of them.  I found
one way off near me, so I resorted to calibrating side roads to
1/100 mile.  Bruce Roe

[The Tassie Devil(le)]

Down here we have in various parts of the State, a set of Kilometre Markers, with large signs indicating them coming up, and there are 5, giving a 4 Kilometre distance.

Years ago, and I am talking about the 60's, we just used the mile posts as timing spots, but when at the bar, it was always the speedo needle that was in the car that was the talking point.

Everyone thought that whatever the needle registered, that was the speed, but it wasn't widely known that the makers always set the speedometer to read faster than actual speed.

When Computers and electronics came commonplace in cars, and people started using GPS's, then it was realised that we were being taken for a ride, so to speak.

Bruce.

PS.   When I joined the Police in 1970, and found out that the Police Vehicles were fitted with corrected speedos, I really noticed the difference.   As a side note, when Holden couldn't supply corrected speedos as per the contract specifications, they went to the supplier of the Falcon Speedos, and fitted those into their Commodore dash boards.

[Oliver Betker]

@ Bill
The pan doesn't look like selfmade. Looks like an original part. Do you have a number of it, maybe there are anywhere something to find. Or I have to look into the parts list. maybe there is it to find.
Until then I could do an improvisational part, to support the cooling. It makes sense I think.
Regards Oliver

[Bill Ingler #7799]

Oliver:  The engine pan is a exact copy of an original pan. Several years ago an ad appeared either on this forum or in the Self Starter advertising the repo of the pans. I think the ad was from someone in Ohio. Maybe it might be found using the Search feature of this forum or someone reading this posting might have the answer. I am away from home so I have no access to my parts book so can`t give you a part number. Maybe someone reading this can give you the number for the pan.  Bill

[harry s]

I bought two of those pans. Exact fit. When this was discussed in a previous thread I tried to find info on the seller but couldn't come up with it. That was a number of years ago, maybe 7 or 8.   Harry