The following tale came about from being able to extract more idle vacuum from my engine. Now that I have some idea of what cam shaft is installed, and a quest to get stronger mid range acceleration, now that the carburetor has been jetted up, and power valve plugged off.

For the last year I have had one or two spare power valves sitting on my desk that have been rotated in and out of the carburetor while tuning. I though nothing of them, and occasionally would rest my finger on the plunger & give it a push. I understand the theory of mixture enrichment and the valve adds additional fuel under prescribed conditions, but never gave much thought as to how the darn things physically operated.

After plugging off my power valve in the old 390 4V in a quest to get better idle quality, and fuel economy, my collection swelled to four valves on the desk. I lined them up as marked: 1â€￾; 2.5â€￾; 3.5â€￾; & 6.5â€￾ Hg, and started feeling the spring & distance the different valves open. Than started to consider just how they do there thing once installed. When it hit me, the spring rates were not sequential in strength…

This became a moment of concentrated pondering, fiddling, and SWAG analyses of spring rates and how they interacted with the different ratings as marked on each valve. The line-up went like this:

1.0â€￾ very very weak spring
2.5â€￾ stiff spring
3.5â€￾ weak spring
6.5â€￾ stiff but less stiff than the 2.5â€￾ valve.

So if one were to line these valves up by spring rate, it would look like this:
1.0â€￾; 3.5â€￾; 6.5â€￾; and 2.5â€￾ Hg

No wonder I have had such a time tuning this damn carburetor, one of my valves was mislabeled, the one I thought was correct according to Holley’s tech pages based on idle vacuum. That 2.5â€￾ valve could be an 8.5" or higher the way the spring feels. Geezemrice almighty for Pete’s sake! I have a call into “Hair Club for Menâ€￾ for an appointment because of this revolting development… LOL

Now that I have better vacuum signal at idle due to a major lash adjustment, my plan is to remove the plug, install a correctly labeled 2.5 power valve keeping the 57 jets in place, and see if there is some more WOT grunt trapped inside my engine.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bill,

More fun from tales of the dark side mystery cam......

Keep us posted on your results.
It will be interesting if the 8.5 PV will keep the door shut and idle stable or if you have to go to a 10.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I never got a bad one new but I have noticed that there are sometimes other numbers on the PV than the ones that say what it is. I usually look for a _.5 number on the right side of the face or on the side of the wrench flat but sometimes it doesn't seem to make sense...

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madam im adam

Is there a missing leading '1' on the 2.5?

Maybe a mark that doesn't quite look like a '1' but is........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ed,

For example, the 1â€￾Hg valve has “Gâ€￾ & 0 as in Zero, the faker 2.5â€￾ Hg valve is in scripted with “Mâ€￾ 2, 5, the 6.5 valve that came with the rebuild kit has “Kâ€￾ at 9 o’clock “8â€￾ at 12 o’clock, “6â€￾ at 3, and “5â€￾ at 6 o’clock.. A the 6.5 valve, starting at 9 o’clock, the 3.5 valve is as follows: “Jâ€￾, 8, 3, & 5. All these numbers are stamped on the face of the brass colored disk surrounding the diaphragm, and are no longer stamped on the hex flats in an easily readable form.

Ted, it is quit the opposite with these valves, one must divide idle vacuum reading in half, and pick the value equal to or next lowest to that ½ vacuum number. A 2.5 would be highest I could go due to that low in gear reading.

In park vacuum is now around 12â€￾, but in gear is much lower around 5 if one averages the fluttering needle on the vacuum gage. If I step up the idle a wee bit I can maybe get a reading where the low side of the flutter stays above 2.5.

I may even try filling the holes drilled in the throttle plates to see if that will improve vacuum at idle, but it probably won’t.

Man I’m getting a lot of bank for my buck fun with this car. The 8 dollar flex plate, freshly re-bolted with super clean threads & jell lock-tight this morning, that keeps giving, and the good old Holley’s continued attempt at intellectual stimulation… LOL

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Ted,

The spring opens the power valve, vacuum holds it closed. A lower number power valve needs less vacuum to hold it closed.

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Joshua

Josh,

Your right! temporary brain fade.......
Hope Bill has better luck now that he has a little more vacuum at idle with his power valve testing.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

No worries.

I was thinking that a power valve tester and an accurate vacuum gauge would be useful to verify the ratings of individual power valves. This assumes one already owns a hand vacuum pump or would buy one naturally.

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Joshua

390 4V? You sound like a F%rd guy when you say that.

Well DartMan, I can see where one would possibly get to thinking “Fordâ€￾ with the mere mention of 390. Sorry for the confusion. However, you are somewhat correct, I do like Model T Fords, and mid sixty’s convertible T-Birds & Continentals, as well as the 1949-1952 Shoe Box Fords & Mercury’s.

I’ll try to tighten up my vernacular in the future to avoid transmitting any scary subliminal messages. How about the old “8007â€￾, that is rather a bit more concise in describing what device I was referring to…

By the way Matt, [url=http://en.wikipedia.org/wiki/Bullitt] Lieutenant Frank Bullitt[/url] double clutched a 390 powered Ford that wasn’t too shabby. You may have seen that flick.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

[quote]Haha,I was pokin fun in good spirit anywho[/quote]

Think nothing of it Matt, I knew you were yanking my chain…

[quote]I believe I now know what movie I'll be renting next.[/quote]

Once you see Bullitt, than it’s on to the second best car chase in movie history; 1971's [url=http://en.wikipedia.org/wiki/The_French_Connection_(film)] “The French Connectionâ€￾[/url], in which pork pie hat wearing, Popeye Doyle, beats the crap out of a Pontiac La Mans as he alternates from WOT to double footed braking while chasing a NYC elevated train…

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC