47 desoto few questions

[hemsbydodge]

Hello everyone,

I need a little advise about the 47 desoto coupe that i have now had on the road over here in england for the last few months.

I have to omit that the old car drives better than i though it was going and the brakes are also pretty good of a car of its age.

Running temperature, when i first put it on the road, it was heat up quickly from cold, even with the thermostat removed. After a head gasket change, head planed, and the valve re-faced and seat cut this helped. Also ,the block was flushed and pressured washed out, and plenty of lime scale was removed.So ,now it runs cooler, but do these engine warm up quickly from cold even with the thermostat removed, it runs at about 160 f when under way, it does drop slightly after a while as well, but it rises when the car is idling, for a few minutes, only to a about 170 F,is this about normal??

Secondly, some time ago i was given a mid 50 s chrysler rear axle from a slant six car, its ratio is 3 .72 could i fit the whole axle casing on the desoto, or could i just change the different assemble as a unit ,to save work?

Thirdly, i have been running a different carb, a rochester one from a chevrolet 235, as it has a manual chock and is a reliable carb as well, the car returns about 17 mpg (uk gallons)or 20 mpg (us gallon) is this about correct?

cruising about 50 ish

thanks for your help,

shaun

[chopt50wgn]

Shaun.................a cooling system has 2 major components, a thermostat and a bypass. The bypass is a loop of coolant that circulates the motor until the coolant reaches said temperature of the thermostat(160,180 etc). As the thermostat opens it now allows the coolant to go into the radiator for cooling.

When you remove a thermostat without plugging the bypass hose, the motor will heat up faster because most of the coolant is going thru the bypass and not the radiator.

[hemsbydodge]

hi, thanks for the posting, i was woundering if this could cause the engine to heat up quicker, i will either plug the by-pass or fit the thermostat,

thanks, shaun

[Rusty O'Toole]

Put in the proper thermostat the engine will run better and get better mileage. 180 thermostat I believe was recommended.

They are a heavy engine with a lot of iron in them. They take a long time to reach operating temp compared to new cars. Yours is probably just getting warmed up when you reach the end of your journey.

The Rochester is a good carb, whether it is better than the stock Carter B&B I don't know. Your mileage sounds about average, in fact very good for an Englishman. For some reason old road tests indicate that American cars in England get about the same mileage as in the US in spite of a 20% bigger gallon. May have something to do with stop and go driving conditions or the way the old road testers used to hammer every car as if it was a racing car.

I wouldn't change the rear axle. I have no idea what axle you have, there is no such thing as a mid 50s slant six car, the slant six was introduced in 1960. They were used in compact Plymouth Valiants, full size Dodge Coronets and jumbo size Dodge Polaras so a "slant six" rear axle could be anything.

If you think changing the rear gear ratio is going to give you better mileage you are kidding yourself. In fact if you think anything will give you better mileage you are kidding yourself. That is a big, heavy, luxurious car similar to a contemporary Rolls Royce, Humber, Armstrong Siddeley or Daimler and it is going to get similar mileage no matter what you do to it. If you want Austin Mini mileage, drive an Austin Mini. There is no other way.

All you can do is pump up the tires, be sure the engine is tuned up and running its best and baby the gas pedal. O yes and put in a thermostat.

[hemsbydodge]

hi folks,

thanks for the help and relies.

I have now had the radiator re-cored, and the heating question has been answered, it was blocked/lime scaled up and now it runs colder than ever,so i can replace the themostat and remove the blank on the bypass .

At present i now have the vehicle running about the best i will get it ,so time to leave along, only one job is the replace the master cylinder with a two stage one, to make the brakes a little better,

thanks ,shaun

[Rusty O'Toole]

It's doubtful a 2 stage master cylinder will make the brakes any better unless the old one is defective.

What will make a difference is returning the brakes to factory specs and adjusting them correctly especially the front ones.

If you want the brakes to work right you need to arc the shoes to fit the drums when you put on new brake linings. Then do a major adjustment so the shoes make full contact with the drums.

If you do this the efficacy of the stock brakes may surprise you. Not as good as 2012 disc brakes but as good as the best drum brakes of its time.

Once the brakes are set up correctly you only need a minor adjustment every 5000 or 10000 miles to take up wear.

By the way what transmission do you have? If it is the Fluid Drive semi automatic it won't work correctly with the Rochester carb. The original carb had 2 electric switches that were part of the transmission controls. If you have a manual transmission it must have been changed because 47 DeSotos had Fluid Drive as standard equipment. Or is it Fluid Drive with a manual 3 speed like a Dodge?

Edited September 28, 2012 by Rusty O'Toole

[hemsbydodge]

hi folks,

well back again. one thing with this old car is that it never ceases to keep me busy, when i thought i had fixed the cooling problem after re-fitting the themostat and removing the blank in the by-pass, it still ran hotter than i would have expected, about 185-190 f even with the new larger re-cored rad?question, if the water distribution tube is defective/blocked ,does this cause the engine to run hotter, espicially the head. using a infra red temp gauge the head always runs hotter than the main block, espically at the rear. the water pump has a re-ferb kit fitted ,so the old paddle impeller is replaced, was this a good idea.

secondly, yes i did know that the rochester carb does not have the two switches fitted to control the gearbox, but once you get use to it, it works fine. .

but as i said the main thing it to find why it run hot, and heat up so quickly, within about a mile/tow and its up to temperature,

thanks for your help,

shaun