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More Power Valve Questions My stock 21 stud engine is incredibly hard to start and runs very rough when it does, will not idle and accelerates poorly. Plugs are sooty black,strong gas smell in cab. I can find no fault in ignition system. I have a holley carb, #91-99. I put a daytona carb kit in it. The Daytona power valve is stamped 5.5 and will drain the float bowl when it is not running or carb is on the bench. Books indicate valve is statically open and pulled closed by vacuum.
I have a hard time believing the float bowl is supposed to drain everytime the car is turned -off. Since the truck has never run before and does not now I also cannot take vacuum readings to select the proper power valve. Lastly, different sources state the "stock" power valve ranges from a 5.5 to a 7.5 and that being off by .5 is detrimental. The carb originally had a #3 stamped on its power valve when I replaced it. I am at 4500' now, truck spent previous life in S. Utah at a slightly lower altitude I believe. So my questions are: 1. Is the power valve supposed to pass fuel when no vacuum is available? 2. What size is standard from factory? 3. How does one make selection if engine doesn't run/idle? 4. How do you test/ measure the valve operation on the bench? Thanks |
Re: More Power Valve Questions 1 No. It should seal. To be more exact, while the valve is technically open, (Vacuum draws it shut) there are no fuel passages that will leak through.
2, 7.5 I think 3, a 7.5 should be ok, the problem is elsewhere. (Actually altitude may play a part) 5.5 should work, I guess. 4, You can't test the operation, but you can check for leaks. I'd be looking at the power valve seat, the radius and the gasket. Lots and lots of previous posts here on 94s running rich. You can get rich running for many other reasons, but as you have a static fuel drain problem, check those items I mentioned above, plus is the valve itself leaking through the diaphragm? the underside face of the diaphragm should not be wet. Mart. |
Re: More Power Valve Questions Daytona makes a fairly good rebuilding kit for the 94. Check all that Mart has suggested. The altitude your at should make very little difference. With the leakage of fuel from the float bowl into the running engine you will experience the hard starts (in essence the engine is flooded) rough idle (TOOO much fuel) inability to adjust idle mixture correctly.
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Re: More Power Valve Questions SofaKing,
Here is my take on your situation.......there are no better kits than Daytona Parts kits. The one issue however is the power valve. The PV functions well and holds up to corn gas with no issues. The rub is there is no real gasket face on the PV. As a matter of practice I machine these PV's to create a proper gasket surface which is square with the threads, flat and exactly the right diameter to trap the gasket of my design and manufacture. The gasket is integral with the PV. I will admit to selling a lot of these babies to whom ever wants them. Charlie ny |
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Re: More Power Valve Questions I really don't know how to put this without being laughed at or getting funny looks, but I just suck on 'em and see if they work (same principle as above). Also, whenever I rebuild a carb, I fill the float bowl with gas and let it sit on the bench overnight. If the float bowl is down significantly the next day, I know I'm not done.
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Re: More Power Valve Questions Good idea Tubman, I do the same thing.
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Re: More Power Valve Questions I suck on em too. Have detected some bad ones that way.
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Re: More Power Valve Questions Quote:
To Mart, Tubman and the rest who suck on them, it occurred to me but I was enjoying a nice homebrew and didn't want to ruin the taste. |
Re: More Power Valve Questions Do a little research on Vintage Speed and Charlie-NY and you will see they are very different.
You have to get the taste out of your mouth some way; I can't think of a better reason for another homebrew. |
Re: More Power Valve Questions Quote:
I am at that happy time in life when no reason at all is sufficient for another beer. |
Re: More Power Valve Questions The advantage of using a vacuum gauge:
1) you can see when the valve begins to open 2) you can see when the valve is fully open |
Re: More Power Valve Questions Vacuum sucks.
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Re: More Power Valve Questions Send your carb to Charlieny. He just rebuilt my Stromberg 97 and it started today as soon as I pushed the button. Never did that before.
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Re: More Power Valve Questions Greg,
As Tubman says I have nothing at all to do with VS, I will say no more. I will check my PM's. Charlie ny |
Re: More Power Valve Questions As FireEngineMike did so did I on my tri carb 94s. Send the carb to Charlie let him do his thing. You'll be happy you did!!
Thx again Charlie! |
Re: More Power Valve Questions Mr. Sofaking, I have been experiencing similar problems with my "94" Carb. I have found that Holley makes power valves for their modern carburetors that are being sold in the rebuild kits for our vintage carburetors. The difference is very slight, but allows the carb. to "leak down". Notice very carefully at the area where the threaded shaft meets the mushroom that houses the diaphragm. The power valves for the vintage carbs this transition is a sharp 90% angle. And used a lead gasket. The modern replacement has a slight radius from the threaded shaft to the area the gasket would seal. Plus the new kits supply a red fiber gasket that difficult to center on the threaded shaft and make a good seal. Take a very close good look.
enjoy your hobby. |
Re: More Power Valve Questions If you have contacted CharleyNY you will get it worked out. Don't worry about getting all the bugs worked out...I guarantee there will be new ones down the road. Enjoy the adventure.
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Re: More Power Valve Questions SK,
Your PV 'kit' is on the way. Charlie ny |
Re: More Power Valve Questions 3 Attachment(s)
Moroso makes a checker for testing power valves. Pn #62295. I don't remember the cost, & I havn't used mine yet. You screw the power valve into it & put the cap with the nipple on it, the plug your vacuum tester on it. Pump it up & see at what vacume level it will pull before it closes. Bill
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Re: More Power Valve Questions About $50 for the tester vs $10 for a new power valve? Might be worth it, especially if you do a lot of carbs. All 5 people who bought one seemed to like it, though. They all gave it "5 stars".
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Re: More Power Valve Questions I have the Moroso power valve tester. It works well. It's the best way I have found to test the power valves. Lets me know if the power valve you have works as-advertised.,...jack
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Re: More Power Valve Questions I have a question about the amount of fuel the PV supplies to the engine when open. Can this be controled?
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Re: More Power Valve Questions The amount of fuel is controlled by the power valve channel restriction. It is a fixed diameter passage in the carb.
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Re: More Power Valve Questions Quote:
Quote:
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Re: More Power Valve Questions There are not different fuel flow ratings on these power valves. Just vacuum ratings when they open.
The fuel flow rate is controlled by the orifices after the power valve as previously stated by flatjack9 in post #24. It would be difficult, but possible to change the restriction size. Sal |
Re: More Power Valve Questions was aware of that, just wondered if there was a mod to adjust it. One reason I like the Rod system.
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Re: More Power Valve Questions Quote:
The two approach holes after the power valve right before the actual restriction leading to the main wells are about 1/4" long and can be opened up slightly with a #21 drill, then tapped to 10-32 thread size. Then you would have to make or buy brass plugs that are 10-32 and drill the restriction to any size you want. You would have to measure the original restriction size ( for reference), then drill them out to a larger size if you use a screw in restriction. Looks easy enough on a 94 I have here. Sal |
Re: More Power Valve Questions I really don't see any reason to even mess with this for any street driven engine.
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Re: More Power Valve Questions Quote:
I absolutely agree that the power valve restriction channels are the fuel metering orifices. Just to clarify, I hope. There are different "fuel flow rated" power valves sold. These ones are four barrel ones originaly. There are stock, standard rebuild pack type and larger "window" sized valves, the original 94 power valve has four small holes for the fuel flow. Now your correct in the fact that it's not the power valve that meters the fuel, just pointing out to those who may have seen these "high flow" power valves and think there on to something. Ron, these original four small hole valves would be the easiest to adapt to a metering valve, as they have round holes on a flat surface. Plug two and drill the other two bigger and make up some little bitty jets, and drill out the power valve restriction channels larger, if you want more gas. I love these original power valves, you can even adjust the spring tension to change the vacuum rating. A pair of needle nose pliers slide between the spring coils holding the centre rod and screw the spring retainer up or down. The retainer is punched to lock it to the thread on the rod, so the first adjustment takes reasonable force, I've not had one brake, yet!. A nicer way to adjust than unfurling the spring, clip off a coil and re unfurling it. One of those moroso testers would tell you where you are and where you've gone. I guess and road test. Though ain't done any for a time. Martin. |
Re: More Power Valve Questions Quote:
I spose it depends on what your trying to achieve? Regular street driven stuff, I'd agree with you. Ron's or like minded folks quest for economy, you gotta look for it everywhere. Martin. |
Re: More Power Valve Questions Being an old putzer, I have a Carter 2 bl, that's about the size of the 2GC. Now this carb has a rod/jet system of fuel regulation. I might consider rebuilding it for a future test on the 280. This engine has been designed to produce a great deal of torque at low RPM's, and after having aprox 200 miles on it, low end torque is better than I expected. It's a 255 Merc engine bored to 3/5/16 +.020. The rest of the engine is stock. except for the carb an dist. I haven't had time to run mileage tests, but that's coming soon.
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Re: More Power Valve Questions Quote:
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Re: More Power Valve Questions I'm talking better than can be achieved with that same light foot. Like getting better mpg at a constant say 70 mph.
Martin. |
Re: More Power Valve Questions The power valve would not be active at 70 mph cruise. The vacuum would be high enough to keep it shut.
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Re: More Power Valve Questions Jack,
The number I used is just a number for an example, not a real situation. Just trying to point out that the search for economy with a flathead is more than just lifting your foot a bit. If we could spuddle around with the carb and make it more efficient, like the delco ignition and using vacuum advance to pull a bunch of advance at cruise, this is the kinda thing I'm talking about. Bit like "Having my cake and eating it" Martin. Maybe if I hadn't eat to much cake I'd get better performance and mpg. but I like cake. |
Re: More Power Valve Questions Quote:
Turns out the truck lived at a higher altitude by a 1000', not lower as I previously thought. Do you have any recommendations for jet numbers for 4500'? I will have to find the piece of paper with what I've got in it. It tends to stall and occasionally pop through the carb right off idle, I assume it is now lean as it is no longer drowning from the leaky PV and a little bit of choke helps. Adjusting the accelerator linkage didn't help, I started at position #2 and it was worse on 1 and 3. I am at 1.5 turns out on the idle mixture screws, another 1/2 turn-out didn't improve things (nor did 1/2 turn in). I am going to play around with it after dinner tonight. Thanks Charlie and everyone for the help. |
Re: More Power Valve Questions Update: Main Jets were 49. Went up 10% to a 55, better but still lean off idle. Went to a 59, much better! Still a little rough accelerating under load, may play with vacuum brake before installing 61 jets. Never adjusted a distributor like the crab before. I am thinking that now it runs and idles I may rig up a vacuum gauge.
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Re: More Power Valve Questions 59s and 61s sound much too big. You may be too rich now, rather than too lean. 51s should be ok. If leaning off idle it may be a problem with the accelerator pump. Think of it this way, If you were able to bolt a stock time warp factory carb on there in perfect working order it would run great. having to fit jets 10 sizes over stock is showing you are not out of the woods yet with your carb setup.
I have also tried 49 jets with no success. Mart. |
Re: More Power Valve Questions SK,
51's are the MAX, even a bit rich at that. The 5.5 PV and 51's will get you in the ball park. It is beginning to sound like you have vac leak , possibly due to an overly loose throttle shaft........very common in well used 94's. Charlie ny |
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