More Power Valve Questions

[tubman]

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".

[jack orchard]

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

[Ol' Ron]

I have a question about the amount of fuel the PV supplies to the engine when open. Can this be controled?

[flatjack9]

The amount of fuel is controlled by the power valve channel restriction. It is a fixed diameter passage in the carb.

[jack orchard]

Originally Posted by Ol' Ron

I have a question about the amount of fuel the PV supplies to the engine when open. Can this be controled?

Originally Posted by flatjack9

The amount of fuel is controlled by the power valve channel restriction. It is a fixed diameter passage in the carb.

I agree. Are different flow-rate power valves available (with the same opening and closing vacuum ratings)?

[scicala]

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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

[Ol' Ron]

was aware of that, just wondered if there was a mod to adjust it. One reason I like the Rod system.

[scicala]

Originally Posted by Ol' Ron

was aware of that, just wondered if there was a mod to adjust it. One reason I like the Rod system.

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

[flatjack9]

I really don't see any reason to even mess with this for any street driven engine.

[scooder]

Originally Posted by scicala

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

Sal.
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.

[scooder]

Originally Posted by flatjack9

I really don't see any reason to even mess with this for any street driven engine.

Jack,
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.

[Ol' Ron]

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.

[flatjack9]

Originally Posted by scooder

Jack,
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.

An easy way for better economy is to have a light foot.

[scooder]

I'm talking better than can be achieved with that same light foot. Like getting better mpg at a constant say 70 mph.
Martin.

[flatjack9]

The power valve would not be active at 70 mph cruise. The vacuum would be high enough to keep it shut.

[scooder]

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.

[SofaKing]

Originally Posted by Charlie ny

SK,
Your PV 'kit' is on the way.
Charlie ny

Thanks Charlie! Got it yesterday, looked great as did the nylon/teflon gasket, put it in and was able to drive the truck around the block; first time since 1973. I still have some tweaking to do but am not nearly as frustrated as I have been the last few months. I appreciate that more than the valve.
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.

[SofaKing]

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.

[Mart]

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.

[Charlie ny]

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