Here's the line up of what I have.the one on the top left is what came in a couple kits.very different and doesn't move and no numbers on it.runs and idles great,revs up great but starves out under load.all the others seem to not run or idle good at all.folks say I need a Stromberg 81 but can't get one anytime soon.i do have a 97 I could try tomorrow .any thoughts would be appreciated.this is in a stock moored 31 cabriolet with a header,intake ,and stock ignition
I don’t know enough about your motor to be of help. Stock Ford flathead V8s generally run 7.5 with a single Holley 94. Would a 2.5 or 3.5 PV or 4.5 open sooner and give more fuel earlier ? What I do know is I have been playing around with different combinations on my flathead V8 and was also running out of power, so checked the little air filter and as it was dirty looking, I removed it and all my problems were solved. ( well, all my problems relating to the lack of power ).
I ran a Holley 94 on a banger with a Winfield head and a Mallory distributor and used a 6.5 power valve with no problems. Did have it quit me once when going up a long hill with a half tank of gas, wouldn't feed gas fast enough, I would check the fuel flow and float level. I have a pair of 81's that I thought about running on my flathead but went with 94's. As memory serves an 81 is around 125 cfm and a 94 is around 175 cfm, if anything a 94 set up right should run rich.
The top left one looks like a spark valve (at least that's what we used to call them) for one of the late 94's used on the Y-blocks...
"warbird1" is correct. That is a "spark valve" and screws into the outside of the base on a later model carburetor. Most 94 kits these days include them so as to cover a larger variety of carb models.
What warbird said. That looks like a spark arrestor valve, not a part of 94s. Aftermarket rebuild kits for 94s are notorious for including the wrong PVs. In your picture the 6.5 and 7.5 on the right and back have an extra ridge or step compared to the others. This is a later model Holley PV design and not compatible with the 94, this will leak and flood your carb. You need a flat surface like the 8.5s and the 7.5 on the left. Can be tricky to acquire, but they are sold. I have had to return multiple. Check Macs.
So, you want to start with a power valve that is about .5 the vacuum at idle...or that is a rough guideline. I know that on the single 94 that I run on my banger, I am running a 4.5 and adjustable main jets. It has a Lion head on it with about 7.1 :1 compression ratio. The power valve closes at any vacuum above the power valve rating. So think of a partial throttle operation where the vacuum is below the 6.5", or whatever value you install, the power valve will open. You are making a pretty good vacuum leak with a 94 compared to a stock A Zenith. I would start with a 6.5 and that is likely to be too fat... As mentioned, you need to be careful also about the radius on the power valve and the gasket. It looks like all the power valves you have a radius at the end of the threads where they meet the body of the valve. That will hold the valve off the gasket and leak gas by the valve....you will wind up being real, real rich thru all throttle operation....especially at idle. There are new power valves out there that have the radius machined off them. Charlie Price has them along with the backfire arrestors. One backfire and a Holley power valve is a ruptured duck. Also, I've had to drill a 1/8" hole in the throttle plates to get enough air to obtain a proper idle mixture....but I am running between 5000' and 7000' elevation. Good luck
The key to the power valve (economiser) is selecting a value that will not open, even a little, when steady cruising on flat ground, when manifold vacuum is highest. But it's also nice to have the juice come in quick when desired. Measure what your particular engine setup, al***ude, etc cruises and accelerates at with a vacuum gauge. If the valve size is cut too close to the bone it will **** major fuel constantly or in a stiff headwind and foul plugs out and ******s selecting correct jet sizes.
So today I went through the carb and the only power valve I have for the 94 carbs are 7.5 or 8.5 so i tried the 7.5.idles great,power is good but from a dead stop to get going it wants to pop and stall.if I give it a bunch of gas it gets through it.so seems like I need more gas off the line like a lean condition?ive ordered a 5-6-7-8.5 power valves to play with .also have the pump setting on 3 witch is the most shot.will report back with results.
Should also mention I had 51 Jets in it and thought that was a bit much so I put in 47's.just checked the plugs and one was black rich #2.put in a new set of plugs since I had em and it idles smoother than before
I agree on the jets. The problem you describe doesn't sound like a PV issue to me. Make sure those valves are compatible with the old 94, Holley sells a lot of parts, many not compatible with our old dilapidated jalopys. Have you changed accelerator pump volume (plunger on left)?
The valves I ordered are for the 94's.ill try different pump settings tomorrow. Unsure what the stock Jets should be.
Hey all my power valves arrived so I swapped in a 5.5 just to see along with the 47 Jets that I had put in earlier.seems great!no hesitation or stumble and seems like 200 rpm more power!used to flatten out at 2200 and it pulled to 2400 no problem.now to find a head and swap out the trans for another that I have with good teeth
The Jalopy Journal
