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T. Cotten
08-07-2011, 10:24 AM
Tommo and All!

I have been trying to apply the 3oz-or-5oz settings for airvalve tension, and some fall right in, occasionally into the original pinning hole, when the original shaft is serviceable.
(Although there may be as many as 14 turns on an adjustor, I have been using 5 for the half-way point, to safely engage the friction pad.)

But Schebler's variations seem endless.
Just the complication of easily swapped airvalves from one carb model to another makes our forensic studies muddied. (I call it "forensic", because there is no literature.)

Attached is a pic of the four varieties of airvalve spring that I am aware of, so far,..
The far left and far right 'conical' examples are meticulous reproductions of NOS examples by FickauPrototypes@cs.com.
The middle 'beehive'-shaped examples are from an H175 and an H154. Note that only the H175 is not progressively wound.

The H175 comes quite close to 3OZ, but the H154 requires that the adjustor be screwed in all the way in, to tension down to 5OZ.
Mr. Fickau's little conical matches 3/4" models I have encountered, but I have yet to find a 1 1/4" model that will accept the very large one, without clipping turns.

Using a spring scale, and a simple calibrated rod, and a plexiglas base that I could look through,
the smallest 1" free-length 'conical' modern spring pulled to 6oz at 3/4" of compression, for a blind baseline.

The longer springs were pulled to an even 1":
The 1 3/16" long H175 'beehive' produced 3 1/4"oz;
The 1 1/4" long H154 'beehive'produce 8oz;
and the 1 7/16" modern 'conical' produced 18oz.

Perhaps the large spring was for an auto!

My immediate quandry is the H154, which must have its adjustor turned all the way in to reach down to 5oz, with its original spring.
Substituting the H175 spring proved much too light.

Is there a spring with a tension between these two?

Thanks as always,

....Cotten

Tommo
08-07-2011, 05:39 PM
Cotton,
I've found that the larger the bore of the air valve, there are 4 different sizes that I know of, the stronger the spring needs to be to be able to control the heavier moving mass.
Those big, strong springs seem to be for the big air valves fitted to the large bore racing carbs.
I've attached a couple of photos of some of my bits and pieces but as my camera doesn't have a close up facility they may be a bit far away.
There is a selection of springs, adjusting ramps and their mating knobs, early to late air horns and a couple of extra air valves.
It appears someone needs to run some sort of session on these carbs at Davenport as it's very hard for me to try and express 50 odd years of playing with these carbs on this forum.
If I ever get to Davenport again maybe you and I should sit together and try and help others better understand these carbs. A few rums would probably get me started.
Seriously though anyone please feel free to ask questions about anything I've posted here and I'll do my best to answer but please realise that even after all these years I don't know it all and there are still things for this old chap to learn.

T. Cotten
08-07-2011, 11:16 PM
Tommo!

I'm afraid that Davenport is a high-pressure working weekend for me, where I push my services like a carnival barker for three days until I am hoarse, stopping only to sleep in my booth when the sun goes down.
In the meantime, I shall continue to post photos of the many variations that find their way to my door, and beg your opinions and insights!
Many digital cameras have a hidden "macro mode" that shows up as a little flower on the control screen. Although I have only held a dozen or so H models in my hands over the last year or so, my photo library is the only way I can keep track of the variations. The '13 3/4" I did for Matt Olsen had only a brass disc for an airvalve, with no room for a leather at all!

I fear I must just drill the H154's replacement shaft for a pin at the same dimension as the original, and leave it at that.

One oddity that really mystifies me are needles that are filed square!
Have you encountered any?

Your input is priceless to us all,

...Cotten