"Power" valves vs. "Spark" valves

tubman

tubman

Well-known member
I am going through a Holley 94 (model 59) carburetor for a friend. The unit appears to be in pretty good shape, but it has been sitting a looong time and everything inside was froze. I finally got everything apart with out breaking anything and am just starting to put it back together. One of the things that is stuck solid is the power valve. It has no functionality whatsoever. I went through my stuff, and found a baggie with eight valves marked "94 Power and Spark Valves". While I've been around the block with earlier 94's, I have never fooled with the later ones with spark valves on the back. Of the 8 valves I have, Nos. 1 thru 4 seem to be new unused units with no markings I can find. To the best of my recollection, these were spark valves that come with the universal kits. No's 5 and 6 have a very small "7.5" stamped in the end of the brass plunger. No. 7 has what looks like a "3" stamped in the same place, but if you turn it 90 degrees counter-clockwise, it looks more like a "(J". No. 8 is wierd, but the large end with the holes looks more like a spark valve to me.

Right now, I am leaning towards using no. 5 or no. 6 because of the stamped "7.5" and they both seem to work. Is there any way to tell the difference between power valves and spark valves, or are they interchangeable? I do a bit with power valves for later Holley 4 bbls, and those are usually marked with their opening vacuum, bu the older ones are rarely marked in my experience. Of course, all of these screw into both spark and power openings which just adds to the confusion. Any knowledge or guidance that you can provide will be greatly appreciated.
 

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#8 is definitely a spark valve. You can identify a spark valve from a power valve because they are spring loaded in the opposite direction. So anything that is spring loaded the opposite direction from #8 is a power valve.


Sal
 
My guess would be that the upper row is spark valves and the lower row is power valves from the springs position...agree with Sal on that the "look" of nr8 is spark valve but the spring position says power valve.
Basicly if you suck from the mushroom side and the valve moves it´s a power valve.
Spark valve moves the opposite way.
 
flatheadmurre said:
My guess would be that the upper row is spark valves and the lower row is power valves from the springs position...agree with Sal on that the "look" of nr8 is spark valve but the spring position says power valve.
Basicly if you suck from the mushroom side and the valve moves it´s a power valve.
Spark valve moves the opposite way.
Click to expand...





Believe me, #8 IS a spark valve. I know the spring appears to look like the it's pushing in the direction of a power valve, but it's not.


Sal
 
In addition, will the diaphragms in these NOS power valves withstand ethanol? And are you sure they're not already leaking after years in storage? And I agree, #8 is the spark valve. The shape of the 'face' identifies it.
 
Sal probably has this figured out but i can´t understand how a springload on the side nr8 has will work as a spark valve...please educate me i really want to understand how that design works...
Here is a few pics of spark and power valves.
First pic is early and late design powervalve.
2nd and 3rd 2 designs of sparkvalves.
 

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flatheadmurre said:
Sal probably has this figured out but i can´t understand how a springload on the side nr8 has will work as a spark valve...please educate me i really want to understand how that design works...
Here is a few pics of spark and power valves.
First pic is early and late design powervalve.
2nd and 3rd 2 designs of sparkvalves.
Click to expand...







Here is a link to a diagram showing how the spark valve works on a Holley 4000 (teapot). There is actually a 2nd spring inside that can't be seen, besides the one you can see on the small end. Kind of complicated, but the inner spring must be stronger than the outer one, because they are pushing against each other.
In the diagram, you can just barely make out the inner spring.


Also, the original Holley valves had the small holes on the outside of the big end. Some after market valves (in kits) had just one big hole in the center. Some also had similar holes like original Holley valves.


Sal




http://www.tocmp.com/manuals/Carbs/Holley/H4000/C228/pages/MCarbHollFLM__55-C228-011_jpg.htm
 
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