Holley 1920 Rebuild Help

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SmokeJumper69

SmokeJumper69

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I just rebuild my Holley 1920 carburetor on my slant six. I hooked everything back up but I can't figure out how the bowl vent rod gets hooked up. Right now the thing gets stuck open and fuel spills out of it. I attached some pictures of how I hooked everything up. It looks right to me but there is something wrong and I can't figure it out. Can someone help me?

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None of your pictures shows anything having to do with the bowl vent. Most of them seem to feature the choke pushrod. No amount of bowl vent linkage adjustment or hookup, however, will cause or prevent liquid fuel coming from the bowl vent. If that is happening, there's something the matter with the carburetor. Carburetor operation and repair manuals and links to Holley 1920 repair/modification threads are posted here.
 
I was over at Charlie's today and remembered to snap some pics of a 1920. Hope these help. Edit: These are pics of a Carter BBS and I have edited the photos so people do not get confused in later searches.

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Those pics will be very helpful, Kevin...

...for somebody interested in looking at pictures of a Carter BBS.

Whoever wants pics of a Holley 1920 will need to look elsewhere.

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Oh well -- I asked Charlie which one. ;-)

He has a lot of carbs on manifolds. Maybe he will be able to take a few pics.
 
I figured out what was wrong. And sorry about missing the picture that ACTUALLY shows what was wrong. The spring that shuts the bowl vent closed wasn't tensioned. I just wrapped it around the rod and it worked fine. However, I drove it up the turnpike after adjusting it and it had no power, I couldn't get her past 70! and went through a tank of gas after the 90 +/- hike from South Jersey to NYC. I dunno what's going on. I adjusted the float using the little cardboard thing that came with the kit and from what I can tell did everything else right, although I still need to get a tachometer to adjust the idle and hook it up to a vacuum gauge to set the idle mixture, I just did it best I could by ear and kept with the "2 turns out" technique that's called out in my Chilton's manual for the idle mixture screw. Not sure if that would cause my problems or not.

Any suggestions?
 
Good job reworking the bowl vent rod spring.

Throw away that useless Chilton book and get the real service manual. There is no specific number of turns the mixture needle should be adjusted to. Each and every individual carburetor, on each and every individual engine, will require a different adjustment. You need to go to this thread and read how to set the idle mixture correctly. Also remember that the 1920 uses a foam (nitrophyll) float, which over time absorbs gasoline and grows heavier than it should be. When that happens, even the correct height adjustment won't cause it to work correctly. Best to install a new float; they are still available though no longer generally stocked at parts stores.
 
SmokeJumper69 said:
I figured out what was wrong. And sorry about missing the picture that ACTUALLY shows what was wrong. The spring that shuts the bowl vent closed wasn't tensioned. I just wrapped it around the rod and it worked fine. However, I drove it up the turnpike after adjusting it and it had no power, I couldn't get her past 70! and went through a tank of gas after the 90 +/- hike from South Jersey to NYC. I dunno what's going on. I adjusted the float using the little cardboard thing that came with the kit and from what I can tell did everything else right, although I still need to get a tachometer to adjust the idle and hook it up to a vacuum gauge to set the idle mixture, I just did it best I could by ear and kept with the "2 turns out" technique that's called out in my Chilton's manual for the idle mixture screw. Not sure if that would cause my problems or not.

Any suggestions?
Click to expand...


Have you ever checked out your gas tank? The filter sock (or whatever they use) may be clogged. That will definitely limit your top end. It could also be your fuel pump, of course.

Edit: At one point in time I owned a Olds Custom Cruiser wagon with a 455. I was having a similar issue and used an air line sprayer adjusted down to just a few psi to "backflush" the fuel line going to the tank. That showed me that there was a problem and I dropped and opened the tank and cleaned it out.
 
Before you run out and buy a float, check the weight. I contacted Holley as to what the 1969 Holley 1920 spec should be. They wrote back this morning:

... it should be 7.5 grams, with a high and low of 6.5-8.5
Click to expand...

Good luck.





slantsixdan said:
Good job reworking the bowl vent rod spring.

Throw away that useless Chilton book and get the real service manual. There is no specific number of turns the mixture needle should be adjusted to. Each and every individual carburetor, on each and every individual engine, will require a different adjustment. You need to go to this thread and read how to set the idle mixture correctly. Also remember that the 1920 uses a foam (nitrophyll) float, which over time absorbs gasoline and grows heavier than it should be. When that happens, even the correct height adjustment won't cause it to work correctly. Best to install a new float; they are still available though no longer generally stocked at parts stores.
Click to expand...
 
I have found that the gas evaporates and float weighs less. It may last about 2 days, then will float like a rock! One problem is the modern additives in gasoline to keep injectors clean. They are hard on many materials and hoses in older cars. One solution I found is to use a brass float, however that may not be available for the 1920. The BBS carb does have a brass float and a carb conversion is possible.
 
How does the fuel proof dope for model aircraft hold up? Anyone know? You might be able to seal the cells with that. I know all the effort is starting to make the time worth more than a replacement float.

You could put the gas and float in a well sealed container in the fridge for a couple days and then quickly weigh the float. The lower temp will depress the evap rate and you should have time for an accurate measurement.

Brass floats have their own problems. I have patched many brass floats with pin holes.


KitCarlson said:
I have found that the gas evaporates and float weighs less. It may last about 2 days, then will float like a rock! One problem is the modern additives in gasoline to keep injectors clean. They are hard on many materials and hoses in older cars. One solution I found is to use a brass float, however that may not be available for the 1920. The BBS carb does have a brass float and a carb conversion is possible.
Click to expand...
 
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