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1920 Holley cleaning
https://slantsix.org/forum/viewtopic.php?t=21644		 Page 1 of 1
Author:  BigBlockBanjo [ Sun Jan 28, 2007 7:27 pm ]
Post subject:  1920 Holley cleaning
Hey guys,
I was looking at the guts from my 1920. Metering block and all...
Just a question. Do they even have power valves? How come everyone says they become junk?
The trash had to just "float" in there, so what would keep you from cleaning it? You can get a wire in most places, and a rubber-tip air nozzle could take care of the rest, right?(with carb cleaner) I can see where the little balls sliding around inside could get in the way.....but are they truely "uncleanable", or is it just a matter of being easier to find another?
I have a buddy that keeps telling me I should put 2 Carter BBS on my intake. I'd rather have the Holleys. He says they won't stay in tune, I say thats garbage. A carb doesn't "fall" out of tune; if it runs right one day, and won't idle the next, it's because it wasn't set right to start with. It doesn't change jets/idle mix by itself. I believe it's just a more tunable "instrument", and therefore more sensitive to change.
I guess it bothers me when I don't understand something that looks simple. (Death to the Rubix Cube!!)LOL
Take care,
BBBanjo
Author:  Rug_Trucker [ Sat Feb 03, 2007 9:40 am ]
Post subject: 
Is that the carb that came on my 198 in 1972? I have one and it has 32K on it. It was a real pain in the butt to start hot even in 50* weather. It always flooded and I had to floor it to get it to start.
Author:  SlantSixDan [ Sat Feb 03, 2007 2:08 pm ]
Post subject: 
Quote:
Is that the carb that came on my 198 in 1972? I have one and it has 32K on it. It was a real pain in the butt to start hot even in 50* weather. It always flooded and I had to floor it to get it to start.
Yep, your '72 came with a 1920 carb, and all the 1920s have Nitrophyll floats, which over the years absorb gasoline and sink. You will want to replace the float and put in a good quality (Walker or Hygrade) kit. And, do the fuel line mod to ease hot starting!
Author:  SlantSixDan [ Sat Feb 03, 2007 3:09 pm ]
Post subject:  Re: 1920 Holley cleaning
Quote:
my 1920. Metering block and all...
Just a question. Do they even have power valves?
Yep. See here for a description of the 1920's "Economizer" (power) valve setup.
Quote:
How come everyone says they become junk?
Different carburetor designs fail in different ways. The 1920's metering block has a great many hidden/blind passages that can become clogged or corroded after a few decades and maybe eight or ten rebuilds.
Quote:
You can get a wire in most places
Don't clean passages with wires! You stand a high chance of wallowing-out the passageway, making it too large and throwing off the carburetor's calibration. And you will certainly scrape away the surface protective coating, exposing the base potmetal and greatly accelerating corrosion of the metal. Potmetal corrodes in very messy fashion, producing white powder that clogs whatever it collects in.
Quote:
I have a buddy that keeps telling me I should put 2 Carter BBS on my intake.
OK, so it sounds like you're running a twin 1bbl intake. My preference is for the Carter BBS rather than the Holley 1920, but as has been mentioned on here before, these days it often comes down to a choice of which can be had in better condition. A new or excellent-condition 1920 is better than a used-up or poor-condition BBS. But condition for condition, I do prefer the BBS.
Quote:
He says they won't stay in tune
A carburetor of fundamentally sound design, in fundamentally good condition, will hold its tune. If one or more of those conditions isn't met, then all bets are off. But yeah, he's wrong. A 1920 in good condition will hold its tune fine.
Author:  Doctor Dodge [ Sun Feb 04, 2007 6:48 am ]
Post subject: 
Over the years, I have spent way more time on trying to get Holley 1920 carbs to work right. Seems that I can get a BBS to work well in a shorter amount of time. I have had some 1920 that would not run well until I swapped to a different metering block. All my "poking, spraying and blowing" would not fix it. I have cut a few of these DOA metering blocks apart and have found what SSDan discribed, corroded potmetal "mold" clogging-up passageways.

1920s work well when they are working but are much harder to fix when they have a problem. If you enjoy a "challenge", take-on the task of "reserecting" a Holley 1920 that has "crapped-out". It can be done but don't be in a hurry.
DD
Author:  BigBlockBanjo [ Sun Feb 04, 2007 12:26 pm ]
Post subject: 
Quote:
Quote:
I have cut a few of these DOA metering blocks apart and have found what SSDan discribed, corroded potmetal "mold" clogging-up passageways.
O.K., I understand......I thought the carb was Aluminum. :roll: I would guess the BBS isn't potmetal??
Quote:
If you enjoy a "challenge", take-on the task of "reserecting" a Holley 1920 that has "crapped-out". It can be done but don't be in a hurry
That's me! I don't mind working a little harder to make something work....thanks for the help!! I see a small light at the end of the passage now! :) (Pun intended)
I'll post when I get the setup working.
Thanks again,
BBBanjo
Author:  Rug_Trucker [ Sun Feb 04, 2007 12:41 pm ]
Post subject: 
Should I disassemble my low mileage one clean and lube to store to stop internal corrosion?
Author:  SlantSixDan [ Sun Feb 04, 2007 1:56 pm ]
Post subject: 
Quote:
O.K., I understand......I thought the carb was Aluminum. :roll: I would guess the BBS isn't potmetal??
The BBS is made out of potmetal (except the throttle body) but it hasn't got such tiny and inaccessible passageways as are found in the 1920's metering block.
Author:  SlantSixDan [ Sun Feb 04, 2007 2:20 pm ]
Post subject: 
Quote:
Should I disassemble my low mileage one clean and lube to store to stop internal corrosion?
It's probably fine the way it is. If you're especially paranoid or storing it in a damp or salt-air environment (yikes!), then spraying some light oil back through the ports visible as you peer down the carb throat should be enough to stave off the corrosion beastie. Fact is, if the Zinc Dichromate passivation coating is present on the potmetal, it won't corrode. If that coating is blasted off or eaten away by improper cleaning methods, it will corrode.
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