Greetings all,

It's been many moons since I last posted. Out of frustration, I parked my car late in 2012 and am just now getting back to it. It has an NOS Holley 2280, 2 bbl (purchased from the same eBay vendor as Reed and others). I have determined that it also has the vacuum-actuated power valve, the same as Reed's 2280, as discussed in this post:

http://www.slantsix.org/forum/viewtopic ... +2280+rich

Here is a pic of my carb:



As you can see, there is no linkage where the power valve would otherwise be - on the left. With this type of valve, as I understand it, lower vacuum pressure causes the valve to open, and feed more fuel when needed.

I have an a/f gauge, and it shows a mix of about 14.5 to 15.0 at idle. When I begin driving, and am feeding it any throttle at all, the gauge goes off the bottom of the scale (which ends at 10.0 - very rich). Based on info in Reed's link, above, I suspect I may have a vacuum leak, which is causing the power valve to open too soon, and close too late. Unfortunately, I have not been able to find a leak in any of the usual locations: rubber hoses/lines or intake manifold gasket.

My questions:

1.) How much vacuum should a 225 normally produce at idle? Mine is currently showing 18 inches.

2.) Approximately how much vacuum should I see at a steady cruise on level ground?

3.) How much vacuum is required to avoid actuating the vacuum power valve on a 2280 (i.e. when should it open, and when should it close)?

As always, many thanks for your help.

Roger

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That is what my shot engine shows. Even my new engine idles around 18". It depends on if your at 6 degrees initial or 12 degrees. The vacuum goes up with more initial advance while keeping the throttle plates closed.
I watch my vacuum gauge like a hawk! it should be between 15" and 21" depending on speed. At 50 it will fluctuate more. At 70 much less and generally higher like 16" to 23".
above 6" typically.

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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

Thanks for the info, Ted. I will try to get a vacuum reading of the engine while driving tomorrow.

Meanwhile, I've been poking around the web, looking for information specific to Holley power valves. I've found some very useful stuff, including how to identify what size power valve one has, and how to determine what size is needed. I also found this page, which contains videos on rebuilding the 2280:

http://www.carburetor-parts.com/Holley-2280_ep_335.html

If this page isn't in our Engine Technical FAQ section, perhaps one of the mods may want to add it?

I'll report back with my findings after more data gathering.

Roger