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1948 Chrysler Straight Eight


Guest 62droptop

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Guest 62droptop

just bought a 48 new yorker straight eight very hard to start when cold looking for help with the coke assembly adjustment.... also semi automatic seems to be working just very,very slow shifting from first to second looking for some advise Joe in Toledo Oh

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Guest De Soto Frank

RE: slow-up-shift - make sure engine idle speed is not too high - should not idle faster than 450 rpm.

Also, if this is your first Chrysler Corp semi-auto, your foot must come completely off the gas while you wait for the upshift... you will possibly hear a "clunk" or notice the car suddenly slow against engine compression - once this has occurred you can step on the gas again and accelerate. It is a deliberate process.

If you can get your hands on a reprint or original factory shop manual, or a MoToR's or Chilton's manual that covers 1946-48, there will be instructions for setting-up the Sisson electric choke.

You might search the Chrysler forum further down the main page here, as both topics have been discussed in previous posts...

Let us know how you are making-out with it...

:cool:

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Guest De Soto Frank

A further note about the choke: there are two parts to its operation:

1) a thermostatic spring that closes the choke 1/2 way when the engine is cold.

2) an electromagnet that is connected to the starter circuit, which closes the choke fully when the starter is operated.

When the engine fires and the starter button is released, the choke falls back to 1/2 open, and the thermostatic spring allows the choke to open gradually as the engine warms.

These worked reasonably well, and were used by Chrysler Corp from 1935 up through 1950.

Make sure all the linkages move freely, and when starting the car, depress the accelerator fully once and release before engaging the starter - this allows the thermostatic spring to partially close the choke and set the fast idle cam.

Once you've established that the choke is functioning correctly, it still might take a little time for you to experiment a bit and find the specific routine that works best for your car...

My New Yorker liked two pumps on the accelerator, then the starter.

One more thing - we have 10% ethanol around here, and any of my carbureted vehicles have the carb go dry if they sit unused for more than two or three days, requiring extra cranking until the fuel pump fills the carb bowl. (The only one not plagued that way is my Model A, with gravity fuel feed.)

Edited by De Soto Frank (see edit history)
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Guest another Ratman

Unless you are going down hill these cars shift slowly. Just think smoooooth and relaxed when experiencing the presto-matic transmission. No jerks and no hurry's mate.... My 1950 Saratoga changes gears when she's ready. Thats ok as she is a 61 y.o. and I'm only 54. so what do I know?

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Guest mschiffel
just bought a 48 new yorker straight eight very hard to start when cold looking for help with the coke assembly adjustment.... also semi automatic seems to be working just very,very slow shifting from first to second looking for some advise Joe in Toledo Oh

:)....drain the transmission of the old oil and refill it with ATF....the oil pump in the trans has a hard time pumping the heavy sludge in it now....the oil pressure built up by the pump allows the spring tension to be overcome causing the trans to upshift.....when slowing down, the spring pressure causes the trans to downshift....don't sweat thev ATF...mopars used it in most of their manual transmissions for decades.....i believe that 10 weight oil is used in the trans from the factory, but you just can't find it anyplace....ATF works very well in my 48 M6 4speed/fluid drive gearbox. :)

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Guest De Soto Frank

Would not recommend using ATF in the Fluid Coupling though... there are reported cases of it damaging the seals.

Universal Tractor Hydraulic Fluid ISO 32 is the recommended substitute for MoPar "Super Fluid Drive Fluid". It is available at Tractor Supply Co. and other Ag suppliers.

First step in diagnosis of slow-upshift is making sure the engine idle speed is between 400 & 450 RPM, and that the throttle linkage moves freely, w/o binding.

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