Revisiting Houdaille Shocks.

[whturner]

Since Ford used these shocks from Model A's through 1947/8, I thought a few comments might be in order.
1) They were designed to use Glycerin - the primary reason was that the viscosity change with temperature was favorable. Other fluids were not recommended, because the temperature/viscosity relationship was outside of design specs, and some other fluids might not be compatible with the packing and seals available at that time. Petroleum based oil was a real no-no. It reacted with the seal around the shaft to produce a tar-like substance.
The resistance could be altered by turning a needle valve. Even so, they found it desireable to add a bimetallic thermostat to further control the flow of the fluid with temperature change. This feature was added somewhere around 1940, so I bet all Ferrari shocks have that advanced feature.
Ford issued detailed instructions on adjusting the shocks for winter or summer use, and/or to suit the customer, who wanted a softer or firmer ride.
1) Glycerin is very hygroscopic, and should be changed on a regular basis. It not only produces rust, but the absorbed H2O drastically alters the viscosity.
2) Do not completely fill the shock - the fluid was designed to be level to the filler plug - with the shock in the position it would be mounted on the car. As Ford says "--- correct functioning of the shock absorber depends on the reservour having the correct air space to absorb the excessive pressure which would otherwise force to liquid out of the shock absorber through the packing".
3) The adjustments are very sensitive. Turning the adjuster 1/32 inch between road tests is recommended.
4) If you are tempted to take one apart, refer to the following post by 250GT.
"John,
This is the manual I use from an other Dutchman Mr. Schaatsbergen.
I think rather good can be enlarged and printed."
link

http://www.tocmp.com/manuals/Ford/Haudaille/index.html"

Observe the various fixtures needed. I have only seen these one or twice at swap meets in all my years. I would save my pennies and farm a rebuilding job out.

Other comments:
With modern materials for seals, and synthetic oils and fluids, it is possible that glycerin and the associated issues have been overcome. I have not looked into that, since my Houdallies don't need rebuilding. (If it ain't broke, don't fix it)
There are some interchanges between Ferrari and Ford - I have run across Ferrari guys at Ford meets looking for Ford shocks.

[DWR46]

Well written good summary. Ferrari shocks do have the thermostats.

[250GT]

Mr.Turner,

Yes. some shocks are compatible is you can find the right ones.
you only need often to exchange the lever.
Once a wellknown prof F-shop proudly shown his found .
N.O.S from France about 40pieces !
Yes they were N.O.S but had offset attachment eyes...
These will not fit without modification
the heat [necessary to bend the part] will destroy the sealings.... such a pity
I mentioned it directly his day was gone.
tja,
No, I am not a malicious joy person.

C.