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I am preparing my1929  '75 for rallies and possibly VSCC Races in the UK.

I would like to run twin carbs and a 4 speed box but will have to justify that the cars ran with theses mods in period, does anyone know if they ran with this spec in period, particularly at Le Mans.

 

 

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They never offered twin carbs or 4 speed that year. They offered a choice of Silver Dome or Red Head (high compression) cylinder head. A year or 2 later some luxury cars offered 4 speed transmissions but they were never popular, they added a "granny low" to the regular 3 speeds. There were overdrive transmissions but they came later.

 

I don't know about LeMans. Chrysler did put up a good showing there and elsewhere.  They were entered by private owners or by Chrysler's European dealers or distributors, not by the Chrysler factory. They may have been modified by the entrant if such modifications were allowed.

 

Those cars were designed to have a wide power band and to do their work easily in top gear. This business of thrashing the gearbox and rowing the car along with the gear lever, to make up for the deficiencies of a weak engine, was foreign to their way of thinking. Get used to the idea of putting the car in top and staying there. To do otherwise won't get you much if anything in performance but will break or wear out the transmission.

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Wow I know not much about the Chrysler 75 but my 65 sedan was still a relatively good performer even with a stuffed engine, I would have thought that there is some other problems or maybe the diff is to high for the body style any way others with more knowledge will chime in but I always thought the 75 were powerful vintage motoring 

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6 hours ago, hawker hurricane said:

Hi Rusty,

It's great when the car is on the flat but i find myself in second or even first on hills, max speed on relatively modest hills is 20mph

There is something seriously wrong with your car. You should be able to take the steepest main road hill in second at better than 20MPH. Most normal hills can be taken in high. 20MPH in low would be appropriate for a slope like the roof of a house.

 

Have you checked your compression? How is your oil pressure? If you are thinking of hopping up the engine with twin carbs etc better take it out and rebuild it first or at least check bearings, cylinders, pistons, oil pump etc etc. Unless everything is in perfect condition it will blow sky high when you hop it up.

 

In those days Chrysler named their cars for their top speed. Any Chrysler 75 would do 75MPH or better, even the 7 pass sedan. Smaller lighter models like the roadster might do over 80.

 

In 1928 a Chrysler 72 roadster placed in the money at lemans with an average speed of 64.56 MPH including all stops. To do this it must have had a top speed of well over 80 MPH. I don't know what modifications if any were allowed at the time. Pictures of a replica show a stock Chrysler roadster complete with folding  windshield, folding top, spare tire, tail light  and headlights but with light weight fenders and running boards.

 

The winning Bentley averaged 69.1 MPH.

 

https://www.allpar.com/racing/lemans-1928.html

Edited by Rusty_OToole (see edit history)

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Rusty is correct. That car should be doing better. The Model 75 was supposed to do 75mph. The Imperial 80 was supposed to do 80mph. And such was the way of the Chrysler model designations of the late 1920s and early 1930s.

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LeMans in the twenties was a form of stock car racing. No racing models allowed, only production road cars available for sale to the public. The first year they required 4 seater touring cars with complete road equipment. The race started with all cars parked, engines stopped, drivers across the road. The famous LeMans start.  They were required to start the race with the top up but were allowed to lower it after completing one lap.

 

It seems by the late twenties roadsters were allowed but full road equipment was still required.

 

All this leads me to doubt that engine modifications were allowed unless such modified cars were advertised and sold to the public.

Edited by Rusty_OToole (see edit history)

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image.png.7a991e5c09912c27675f558511a8f58e.png

 

One of the LeMans Chryslers. Note full road equipment including stock running boards, top, windshield etc and sketchy fenders.

 

Entered by Grand Garage Saint-Didier Paris. Presumably the French importer or main dealer.

 

I still don't know if the engine was modified. I'm inclined to doubt it as this was an endurance race for production cars.

Edited by Rusty_OToole (see edit history)

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What differential ratio is in the car?

 

What tires are you running?

 

I had oversize tires on my 1930 Dodge Brothers 8. It went nicely on flat country - easy cruising at 50 to 55 + 7% (the 7% was the under reading of the speedo). But on the hills it was a bit breathless, sort of as you describe. Now I have the correct tires on and it is a different car. Screaming on the flat, zooming up the hills in top gear.

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If you plan to compete in VSCC races, maybe you should research Ray Jones, Australia. Ray was well known for building and racing very competitive 75's

Unfortunately, Ray passed away some time ago, but I'm sure you wouldn't need to look too far to find some helpful information.

 

Your 75 should definitely perform a lot better! We have several 20's and 30's Chrysler's, and they all climb well, and cruise comfortably at 50mph.

They are not modified, except for changing to 12volt. I have friends that have fitted twin carbies, and they do improve performance, but all retain their

original factory gearbox.

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19 hours ago, keiser31 said:

Rusty is correct. That car should be doing better. The Model 75 was supposed to do 75mph. The Imperial 80 was supposed to do 80mph. And such was the way of the Chrysler model designations of the late 1920s and early 1930s.

The speed rating was for the sedans, the roasters and touring cars were faster. The Imperial touring cars 90ish MPH, roadsters  could do near 100.

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19 hours ago, keiser31 said:

Rusty is correct. That car should be doing better. The Model 75 was supposed to do 75mph. The Imperial 80 was supposed to do 80mph. And such was the way of the Chrysler model designations of the late 1920s and early 1930s.

 

Oh boy !!

I better get the 300 out on the open road.

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Chryslers had considerable vogue in Europe and in England in the twenties and thirties. They were considered a fast car especially the roadsters although by no means a sports car. But they could match the performance of many sports cars that sold for a lot more money.

 

Your Chrysler 75 in its salad days would give a 4.5 liter Bentley something to worry about, and soundly beat a 3 liter Bentley.

 

In America the first Chryslers with their high compression engines, 4 wheel brakes and low built chassis were ahead of their time and handily outperformed larger, more expensive cars.

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Those old flathead engines can fool you, especially the Chryslers. They will continue to run in an advanced state of wear and decay without a lot of knocks and bangs. They just get slower, harder to start and burn more gas and oil. A compression gauge, or a vacuum gauge will tell you if the engine is worn.

 

If compression and oil pressure are good and the vacuum gauge indicates a good engine then it must be a tuning problem of some kind.

Edited by Rusty_OToole (see edit history)

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The Red Head would be a great addition but at the end off the day if the car is not performing as it should with the Silver Dome this isn’t going to solve your problem but if you are thinking rebuilding and adding it and one is available go for it

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On 7/2/2018 at 2:14 PM, keiser31 said:

Rusty is correct. That car should be doing better. The Model 75 was supposed to do 75mph. The Imperial 80 was supposed to do 80mph. And such was the way of the Chrysler model designations of the late 1920s and early 1930s.

The red head gave more horsepower, and the roadster had faster gears, as well as a lighter body. Before my kingpins went bad, I have had my 65 roadster doing 70. Of course an engine rebuild or two over the years helps, but then how in tune and performing is a seldom run car?

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Very many thanks to all who have given their input. I have decided that the best approach is to rebuild the engine to its original  specification, the 'red head' is away being laser welded, the rad being repaired and the engine is scheduled to come out in a week or two.

I will keep you posted,

 

Many thanks,

 

David.

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I seriously doubt the blocks interchange. I believe they brought out new six cylinder engines in 1934. These were the first engines with insert bearings instead of poured babbit. They had water jackets at the top half of the cylinders only. After a couple of years they redesigned the block for full length water jackets. This required moving the starter, altering the block/bellhousing interface, and changing the flywheel. Engines from before and after this redesign will not interchange. I believe the modified engine started in 1937. Engines will interchange from 1937 up to the end of production which was 1959 in cars, 1962 in trucks, 1968 in military vehicles and 1972 for marine and industrial engines.

 

You could use a later engine but it would require adapting. Possibly using the later transmission. I don't know if this would be allowed in your racing rules.

Edited by Rusty_OToole (see edit history)

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If all you wanted was a fast running flathead six without regard to authenticity you could use a 265 cu in Chrysler Windsor six from 1950 - 54 along with a late model 5 speed transmission and modern rear axle. Suitably hopped up, you should have a top speed well over 100 MPH.

Edited by Rusty_OToole (see edit history)

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If you have a look at www.crankshaftcoalition.com (click on 'engines' then, 'MOPAR inline flathead engines') there is a table listing all the models of the Chrysler flat head six,

giving - year, model, displacement. It could be a handy reference point to compare models!

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I have studied the subject of Chryslers at Le Mans for 20 years+ and have talked to Martin Swig, Ray Jones and Chrysler modern day racers too; and I  have looked at the tricks possible to get away with at LMC and VSCC. Appears that there is a lot of hogwash in the UK on these cars. E-mail me via flathead323@gmail.com and I can give you some inputs. The comments you have received are all good, but may not pertain to what would do well at LMC.

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