Power Valve

[oakknoll]

Ok, don't shoot me, I know it has been talked about to death, I looked through the achives but could not find the answer. I have a question about replacing the Power Valve on My J-10. It has a 360, and I am still running the stock Motorcraft 2150. What is the best source for the valve? Where are members getting them and which ones are good or bad? I remember seeing a discussion about it, but I can't seem to find it. Thanks!

[AwesomeJ10]

Back when I still ran carbs, I seemed to have good luck getting the rebuild kits from the local parts stores. They usually include a PV and are like $15.

Now you know there are different PV's right? The difference is they 'come on' and 'come off' at different vacuum levels. Good for tuning the way the engine runs.

[acct21]

There are two kinds of power valves for the 2150 -- a single stage and a dual. The single stage opens fully when the vacuum drops below a certain threshold, and allows the greater fuel flow at a time the engine is asking for more (say, between 1/2 and 3/4 throttle). Most single stage power valves are rated to open between 2.5-10.5"Hg, and will typically be marked with the level at which they open. A dual stage starts to open at one level of vacuum, and fully opens when the vacuum drops even further. My understanding is that this was meant as further fuel economy/emissions features, but doesn't really work well for either. Holley has apparently discontinued making dual stage valves.

The single stage is the one that looks like a mushroom -- the top one. The dual stage has a longer nose, as well as a part that extends below the flange. The one on the bottom in this picture is a dual stage.



In order to even run a dual stage, you must have a dual stage (deep) power valve housing on your 2150 -- in order to accommodate the bit that sticks out below the flange. Here is a photo of a dual stage (deep) housing:



This isn't a great photo of a shallow (single stage only) housing, but you get the idea... if your housing doesn't look like it could accommodate a dual stage valve, you probably have a single stage only. This isn't exactly a bad thing...



If you are still running all of the original emissions equipment, and/or you have a few vacuum leaks here and there, then you can get a replacement power valve in the carb rebuild kits that Autozone, NAPA, etc carry. It will probably work fine.

If you have a strong engine that can pull 18-20"Hg vacuum at idle, the replacement dual stage power valves in these kits will give you a really nice, long flat spot at 1/2-3/4 throttle. This is a lean "bog." The engines just don't drop vacuum enough to open these power valves all the way -- at a time when you need the extra fuel from the power valve circuit.

If your engine can pull a really good vacuum signal, a good estimation is to take your max idle vacuum, divide it by half, and use that power valve in your carb. My engine would just make right at 19-20"Hg, so I run a 9.5 single stage (in a dual stage housing -- it doesn't matter).

You can get replacement Motorcraft power valves, but they are difficult to find. The Motorcraft valves are Holley pattern, but the Holley single stage power valves are about 1mm too short to thread into a 2150. They need just an ever-so-slightly longer threaded area to work.

Quick Fuel power valves work perfectly. They are longer than the Holley power valves, and thread just right into the 2150. They are super cheap, and everyone (Jeg's, Summit) carries them.

[FSJunkie]

NAPA has both single stage and dual stage PV's available by themselves, no need to buy a kit.

Every Jeep 2150 had a dual stage PV. The emulsion circuits are designed to work with the dual staging, and a single stage might cause rich or lean spots in the fuel curve.

A typical dual stage PV kicks in the first stage ~10" Hg and the second ~3" Hg.

[acct21]

I had the dual stage -- listed as the "replacement" part for my engine -- and it gave me a really bad flat spot under partial load. Replaced it with the higher single stage and the flat spot disappeared.

YMMV.

[tgreese]

NAPA has both single stage and dual stage PV's available by themselves, no need to buy a kit.

Every Jeep 2150 had a dual stage PV. The emulsion circuits are designed to work with the dual staging, and a single stage might cause rich or lean spots in the fuel curve.

A typical dual stage PV kicks in the first stage ~10" Hg and the second ~3" Hg.

Check the prices. The 2-stage PV from Napa may be as expensive as the complete (correct) kit from one of their competitors.

I recall that there is a big price jump between the kits with single-stage valves and those with the 2-stage valves. If you find a kit listing for your 2150 for $20, it likely has the wrong or no power valve.

[oakknoll]

Thank you for all the great responces. I learned something. I did not know there were different valves, I thought they were all the same for the 2150. I will pull the carb and see what is in there and order the correct one.