Ok- guys, heres a pic. I don't know much about the 94's, but I do know that this has a threaded end that allows you to tighten or loosen spring pressure for the valve thus changing the opening pressure of the valve. You decide, I tried to find something like it to no avail. Anybody know if these were made by the factory? I also noticed the bleeds are holes not slots around base. The motor was built by Clay Smith in 1946.
They really were not intended to be field adjustable. But if you REALLLLLY had to it could be done. Some way to apply a variable vacumm source to the control side, and away ya go.
I am pretty curious- it has no marks as to the vacuum rating, so I wonder if these were set high, low or what... would love to know what my carbs are set at- without a stamp I really have no idea. It ran like a raped ape until it wouldn't start one morning and was flooding... float was taking gas, but I decided to rebuild carb while it was off and noticed this curious valve... hmmm any guesses??
I think you may find that vacuum holds the valve closed and as you accelerate or climb uphill/load the motor that the vacuum falls away and the spring pulls the valve open.At idle the vacuum is the highest and decreases as the load increases.The diaphragm(actuated by vacuum) holds the power valve on its seat until the vacuum drops and is overcome by the spring.To the best of my knowledge,which is not that great,you can buy different rated power valves.The lighter the spring,the later it opens.I'm sure someone could correct me if I have put you wrong.I tried to get the lightest spring valve so as to hold it closed longer only to be sold a holley valve which did'nt fit as the flange that seals in the body is a different size. Most of this info I got out of an old ford/merc manual.As john evans said they are not really adjustable.Hope this helps.The thread that you see must be where they set the correct vacuum range at manufacture.
Moroso sells a gizmo that you screw a power valve into and then you connect a hand vacuum pump to it and you can see the power valve operate and read the amount of vacuum need to keep it closed. I don't know if your power valve would screw into it or not, but if you have a vacuum pump you could make the gizmo that it could screw into, the hardest thing is getting the tap for the thread pitch (nat'l extra fine?) Usable range (excluding oddballs) is generally 6.5 (stock/mild cam) to 4.5 for a bit of a lumpity cam. Vehicle weight has an effect as well, heavier car wants a higher vacuum rating for some reason, i suspect it has the engine under a greater load. Somebody else may chime in and spread a little light on the weight thing.
The adjustment you have (I think--picture is very fuzzy here) is not meant as a field adjustment...it was used to set the thing to spec at factory, and then the nut was crimped to stake it. Obviously it can be made to serve for field adjustment, though! In the years of carbs I use, '37-48 types, '49-51 probably the same...Ford bulletins show only 2 valves, unmarked Ford and "A" stamped Lincoln. No vac spec shown, as of course they were OEM replacement parts. Looks like the oldest ones were also the "adjustable" design. The vac gizmo can be used for setting to a guesstimated right value...you may need an O-ring to fully seal Ford valve on 4150 design tool. The it is all experimentation. At least parts are fairly available...Rochester 2g people can only swap pieces from other carbs or snip/stretch springs on their vac valves. Weight guess...in heavy car, engine is going to spool up more slowly from the load. Carb behavior will differ because sufficient airflow to get venturis going comes in more slowly, and carb is mostly delivering via off-idle circuits longer.
Wow- great response- thanks guys. With so much talk about power valves and multi carb set-ups, I wonder why someone hasn't made one with marks on it to vary the pressure +- 5 or so..... although it's probably a great way to lose money as the market is so small! Regardless, the motor runs great with all 3 carbs fully set-up with power valves, chokes and all, I'll try to post any specs I can for future reference. Thanks again. -Rick
I just wish they'd make on that fits... Imagine a blue-sky redesign...central stud rotates, has allen head at bottom, springloaded seals allow it to rotate in diaphragm without leaks...hole below it in throttle body, equipped with a simple plug, allows you to turn it on the car. A whole new hobby, twiddling with your valve!
I'm telling you- lets do it! We would make at least $1.10 cents on the venture.... but we'd see a lot of happy faces!
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