I have a 331 Caddy with 4 94's on it. Well it was running pretty good but I wanted it better. I called Charley at Vintage Speed and ordered 2" carb risers, leather pumps and the little acc. pump helper springs. Well Charley said I need to block off my power valves , so I order his block off's. Well now it loads up really bad and misses at idle but performs real well speeding up. I heard that if you block the power valves you need to richen up the carbs, but mine is loading up . I thought a power valve helped under exceleration. Someone explane a power valve.
Dirty2, I can not explain them to you, but all I have ever had with a power valve in a carb is nothing but problems, especially when backing off suddenly after heavy acceleration. They would blow and then run like shit, if they even ran at all. Hopefully someone can answer this for me, as I would like to know exactly what their purpose is as well.
All I know much about is holley four barrels, but the theory should be the same. When you block off a PV in a holley rule of thumb is to go up 8-10 jet sizes. Could one of your plugs be leaking and letting fuel in causing it to load up?
Power valves much like the name implies are for enriching the circuit (for increased power). Vacuum holds them CLOSED for light throttle cruising /economy. When you hammer the throttle vacuum drops (more than "normal") and your Power valve OPENS. The purpose is to give you the best of both worlds - economy / power. The carb is designed for them which is why when you "NORMALLY" remove them you are left LEAN (which is why you usually increase teh jet size to make up for this. But with your 4 carbs that may or may not be desireable - you may be pretty fat already - so removing the p/v may not need the increase in jet size as is normally reccomended. Lots of ways suggested how to select your p/v, but the one that makes the most sense to me is to simply drive around with a vacuum gage hooked up and see what your light throttle driving vacuum numbers are. Select a p/v rating numerically LOWER than your lowest number. (edited - what in the world made me previously type "higher" -oops Some people refer to this as a "higher" opening point - not sure if that's what I was thinking or if I just had my haed in my a$$ - in any event it's confusing ) This way when you HAMMER the throttle the p/v will open. A wild cam can make things interesting at idle - if the fluctuations are so great that it dips below your P/V rating yhen you'll need to readujst and go even lower on your P/V to keep it closed at idle. Now the thing I often wondered is why so many guys rush to remove them (at least on the street).
I'm of no help - but I'm pretty sure that Dave "Littleman" blocked all 6 of his power valves in his A pickup - maybe you could PM him about this thread and have him chime in.
Thanks for all the replys. HemiRambler, that is what I always thought powervalves did. I think my rich problem is a leak or something else.
Old school tech. Take vacumn reading at idle in gear, divide by 2, that is size power valve to use. ex: 7lbs vacumn, 3.5 power valve.
I made a setup, I will drive around with six vacumn gages mounted on top of each carb, I do this when I am syncronizing all six carbs, I can see all six from the drivers seat....The definition of power valve function above is correct.....my reasoning to eliminate my power valves was a simple one.........It just did away with one more possible mechanical problem and another thing to add to the mix.............Its taken alot of work, but its performance cannot be denied..........Again you do not know if something will work unless you try it.........sometimes theory will only buy you a cup of coffee..........and I hate coffee........My 6x2 intake was not designed for the street when they made them and designed them way back when........but you can get them to work........alot of people bolt them on and alot of them do not get used..but with some hard work you can dial them in, their are alot of variables........but speculation will get you no where, unless you have actually tried it and ruled it out...........Dirty2, keep a notebook to document your every change and effect, Good Luck Litteman, keep at it and you will get it...............I remember Charlie once told me to jb weld one side of each of my squirters in all six of my carbs because he claimed I was getting too much fuel.........ha ha thats insane advice, so you have to ask the questions and weight the answers and choose your move.........in the end I ended up drilling out my squirters even larger..............
Kind of what I was thinking. I have, for once been keeping notes. I wont let this beat me. Thanks for the help. Danny
Power valve-usually spring loaded valve plumbed into the main fuel circuit. Now introduce vacuum when engine's running. Vacuum holds the valve shut against it's spring, keeping it closed (most conditions). LOW vacuum, under load/accelleration the spring overcomes the lack of vacuum, opening the valve to richen the mixture demanded by the load/accelleration. If i wrote this right, you'll see there's NOT a lot of reasons to plug one. BUT, if you do, it's very necessary to richen the mixture. Richening the mixture ALL THE TIME reduces driveability. Usually Drag only cars can get away with this. If you can't get it to run right, you probably have OTHER issues
ya need power valves! I blocked mine off and lost a whole second on my time, Im running 3.5`s now with two 94`s and man it run`s great! running stock 7.5`s will kill you with raw gas fumes. there`s some great carb info if you search holley 94`s. call me if i can help. Casey 512-825-5547 man I`ve had some time playing with those thing`s. for the last ?..dam im old !....
Danny, If you were gonna strictly drag race, I'd understand blocking them off. For street use, you should leave them in and tune them right. PVs do need to be tailored to the engine. The best I've ever done with them is installing a vac guage and checking it at my HIGHEST normal cruise speed. Then select a valve rated 2" less than that. When you hammer the throttle to pass or leave a light, the vac will drop below that level and give you the fuel to get away. Missing the right valve rating by even .5 will be problematic, so try several.
I'm just courious how you have the four carbs set up linkage wise - progressive or non-progressive?? Thanks.
The intake I have the only way you can set the linkage up is non-progressive. I have a hurst 6 X 2 that I could make progressive but I need 2 more carbs. I am going to go play with it today. Thanks for all the help. I finally got the 2G tri power stuff mastered and thought I had the 94's pretty well figured out. But I aint giving up. Danny
I have to add that I don't like Charlies open-plenum 2" risers. I'd ditch those quickly & if you want risers, find or make some with indivisual runners. You need a reasonably strong signal to the venturi on these older carbs to get them to run well & the open plenum of the spacers muddies it up - especially if you're running 4.... Just my thoughts. But what else have you changed? Hard to diagnose multiple changes like this...
Well I put the powervalves back in and reset the floats and it runs better than ever. I think I have always had the floats set wrong. Thanks for all the help. Now I need to figure how to get more vac. to the vac. advance.
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