One other thing to add. The power valve is open to manifold vacuum. When the engine is shut off warm, fuel vaporizes and then will condense in the cavity behind the power valve. If the power valve checks good and the gasket is OK then that is likely where the moisture and discoloration is from.

Although it doesn't sound like this is your problem.
There is a "fix" for leaking holley power valves that are caused by backfires. Holley makes a kit.
https://www.holley.com/products/tools/carburetor_tools/parts/125-500

A little trivia.
Back in the 80's with Fords variable venturi carburetor this vaporization issue cause the rubber diaphragm to deteriorate and since vacuum and the diaphragm was what controlled the ventura there was no throttle. The Ford fix was to drill a drain behind the diaphragm. I had a lot of customers request that I convert the Variable Venturi  to a holley 2bbl back in the day..

Dave

I don't think that is the problem given that the symptoms point to too much fuel, causing flooding.  It will be easy enough to test with a remote fuel source and fresh gas, though.  We'll see how it does after I clean it up and put it back together with new gaskets and power valve.


Lawrenceville, GA

The photos of the brown stuff and your description of it sounds a lot like Phase Separation. Where enough water gets into the fuel and causes it to separate into little bits that are soft. Eventually bacteria can get in there. Also the water will rust metal. At this stage of separation : with fuels that have Ethanol in it it will harm the engine when running, with Conventional fuel it does not harm the engine when running. Either way the engine will misfire.

https://www.epa.gov/sites/production/files/2015-09/documents/waterphs.pdf


1936 Ford 3W Coupe : 56 T-Bird 312, 47 Packard 3 speed, 40 juice brakes.
1968 Merc Cyclone FB GT 390, Getting a better front clip!
1977 Ford F-250 Supercab RWD Explorer Long box.
1976 Chev Camaro RS LT
Future rebuild : 1949 Ford F-1

All good questions.  Looks like you need a finer screened fuel filter.  My experience with power valves has been if the power valve holds a vacuum, then the gasket is the problem.  Those gaskets can be touchy in remaining centered on the power valve when tightening them to the metering block; if not centered then fuel is allowed to seep into the power valve cavity in the main body.  When in doubt, just replace the power valve.

Lorena, Texas (South of Waco)

I did find some sediment this time.  It starts out somewhat coarse and disintegrates as I rub it between my fingers until it can't be felt.  I see it in the float bowl and on the float bowl side of the metering block.  I don't see evidence of it on the other side of the metering block or the main body.
Is this contamination due to inadequate filtration?

I also got the power valve tester and the valve is a 7.5 that is fully closed at about 6psi according to the gauge on my vacuum pump and moves smoothly between 0psi and 6psi.  I don't know how accurate the gauge is.  It does hold vacuum.  The portion of the diaphragm that can be seen looks wet.  The pintle and seat look ok.  There was also fuel in the power valve cavity of the main body.  The power valve gasket was moist with fuel but the valve was tight.  Given that part of the gasket is exposed to the fuel, I don't know if that necessarily means anything.  The power valve cavity and corresponding area of the metering block have black residue consistent with what I have seen when fuel has been seeping or leaking for a while.

Can a power valve test good but still be bad somehow?
I'm thinking that the actual cause is either the metering block gasket or power valve or power valve gasket.  I'll clean it up the best I can and if it seems like a full rebuild is in order afterwards, then I'll have a good excuse to try the new 670 that I have.











Lawrenceville, GA

I have a power valve tester made by Moroso that works good in conjunction with a hand held vacuum pump.  I typically use it to check the vacuum rating but it also checks for leaking diaphragms.

Lorena, Texas (South of Waco)

I replaced the pump with my lower pressure spare and the pressure is now under control.  I reinstalled the float needle / seat and am able to adjust the float level and it doesn't seem to be flooding because of pressure or float / needle related issues anymore.  The problem still exists, no matter the float level so I will dig deeper.

Is there an easy way to test a power valve or is it just easiest to replace it and see what  happens?

The Carter does not seem to have an externally accessible regulator.  Maybe I'll take it apart to see how it works.  I couldn't get the Holleys to last.  It is a much different design, and made in the USA, at least 7 years ago, they were.

When I said powder, I was only using that to try to describe the texture of the o-ring.  I did not notice anything that was actually powder or grit.  I've had the bowls off a couple times over the years probably 2-3 years most recently.  It's always been clean.  Who knows, maybe something has changed since then.  I'll find out soon.


Lawrenceville, GA

Charlie, I’ve owned several Aeromotive pressure regulators. Boost referenced, EFI, they all just work. If yours doesn’t pull it apart and look for contamination. This doesn’t address the pump problem, but I’ve gone from 5lbs and boost reference to 40 lbs for EFI by just changing the springs in them. If its passing more pressure, it’s got to have junk holding it open. IIRC they are all alcohol rated, and the springs come in pressure ratings so look for something upstream from it. Or a spring the pump is pushing past.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

What does the carb say for max pressure? If less than 12 it may be too much pressure for the needle and seat.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Do you have a separate pressure regulator in the line,  or are you relying on the pump alone?   I don't think the carb problem is related,  your not overflowing at the bowl.   The only thing that might mess with that is if the regulator starts working or allows the pressure to drop all of a sudden and you lose flow to the carb . 
The white powder in the carb is from the alcohol eating into the zinc of the carb.   I'd suggest a rebuild.   I went through that issue about 5 years ago.   I got a big load of alcohol in my gas.  It ate into the bowl a little and I had quite a bit of that white powder  in the bottom of the bowl.  It actually plugged up my idle circuits and was eating up the rubber in the accelerator pump.  I did a rebuild and it fixed everything.   2 barrel Holley