Got one from Daytona Parts company.
If I have one, why am I posting?
Because I wasted hours getting it, mostly because of bad info on the web, uninformed parts people and a general lack of correct information from end users.
I figure it may help some other schmuck to know about this puppy.
The spark control valve is what Ford used in many vehicles to control the vacuum to the distributor advance.
While other companies used centrifugal combined with vacuum advance, many Fords used only vacuum.
To make this work, they used the spark control valve to 'meter' the vacuum, thus allowing it to do the work of two advance methods.
This was probably just to save bucks, but who cares, it's the way it was done.
The spark control valve looks like a power valve and you find them in Holley 1940's (used as a replacement part for the Autolite 1100,)
You find them lots of other places, like the Autolite, but I'm playing with a Holley 1940.
Misinformation on the valve found lots of places include;
You don't need it.... True if you like flat spots, stalling, etc.
You can replace it with a power valve.... True, you could also replace it with a piece of cheese. That won't work either.
You can't test it.... Um, yes, you can, easily about three or four ways.
You can't buy one.... Um, yes you can. But it's 12 bucks plus shipping.
I assume some parts places have them, why not?
The local shops (8 of them) could not find a number, a part, or a vendor.
One guy from Napa found the vendor, whom I called from home as they do retail sales.
The nice people at Daytona were quick, and the part works.
In fact, you can see the darn thing work. The rubber seal visibly moves in and out as manifold vacuum changes. The timing hops around nicely as well. With a stuck one, a leaking one, or the wrong one, your idle may be shot, you may have dead or flat spots etc.
Just rebuilt this carburetor, but of course the spark control valve doesn't come with the kits, so with a bad SCV it idled wrong, had flat spots, as the timing advance was not working and the mix was too lean from the valve leaking internally.
With the new valve (which does not look much like the old one) Car starts, runs great.