What is this stuff gathering in my carburetor?

[cleandan]

Back story:
Truck that has been sitting unused since at least 2010.
Fuel tanks were empty.
We added about 5 gallons just to get the engine running after prepping and priming first.
With new fuel the tanks now smell like varnish rather than gasoline.
I've got two fuel filters inline as sacrifice filters to help catch anything we unleash from the old tanks...so far nothing of any substance has been caught in the filters...not even mild debris...which made me hopeful.

The problem we are experiencing is a fine, grey powder like substance clogging up the carb fuel bowls and accelerator pump system to the point of jamming things up and stopping function.
If you have ever used a product called "Rotten Stone" polishing compound it looks exactly like that.
The grey powder does not seem to be suspended in the fuel and there is nothing in the fuel filters (pleated paper in a clear case and about 2" in diameter)...not even discoloration.

Today will be the third time the carb has been clogged by this grey substance with about an hours run time total.

I am starting to think the fuel is dissolving the carburetor body and metering block.

This carb was a used carb purchase (Holley 670 avenger) and I went through it before our first use and things seemed fine, but the metering block did have the appearance of losing its finish.

If you have any ideas what might be going on I would be happy to hear it...I'm stumped on this one because I have never seen anything like this before.

[6667fan]

I have seen powder that is more white than grey from gas that contains ethanol. Collects in bottom corners of float bowls.  Took apart my buddies Holley for him and there was so much in bowls I asked him if he had been hanging at beach with his car.

[cleandan]

I have seen powder that is more white than grey from gas that contains ethanol. Collects in bottom corners of float bowls.  Took apart my buddies Holley for him and there was so much in bowls I asked him if he had been hanging at beach with his car.

This is certainly not the ethanol grey powder I have also seen.
This stuff is the consistency of talcum powder and the color of JB weld grey (it does not get "wet" in the fuel either and turn into a paste. It stays dry even in fuel)

After testing a few things (I'm not done yet) it is looking more and more like the Holley metering block is disintegrating.
I don't know why, but that seems like the most reasonable answer at this time.

I have checked the filters carefully and there is no grey residue of any type, let alone the large amount I have found in the carb fuel areas.
The secondary float bowl does not have this grey residue.
I have pumped some fuel through the trucks system and into a clear container and there is no visible particulate, and there is no settling particulate.
I ran an Autolite 4100 on this engine for a little while (until I found it leaking at all welch plugs, which are being repaired) and that carb did not have any grey dusty residue in the bowls.
I am currently running an Edelbrock carb and that too has no grey residue.

I don't know what else to test within this system to help me figure out what is happening.

I'm going to remove the primary metering block and drop it into a container of gas and see what happens.
If grey dusty residue precipitates, I think that is pretty definitive concerning the metering block dissolving.

What do you think?

[GerryP]

The zinc in the carburetor is probably disintegrating.  Zinc powder is a dark grey/blue color.  While gasoline is generally neutral, there may be additives that have become or are acidic, particularly high levels of sulfur or bad storage conditions.  It's hard to measure that so you end up accepting the symptoms as the evidence...unless you can send the fuel off for analysis, which may be worthwhile.  Blackstone does fuel testing. 

[Riderjeff]

Have you reached out to Holley?