Float Adjustment - 1965 401 Rochester 4GC (solved - I think)

[Brtele]

I’ve been trying to find the float adjustment specifications online yesterday/today and coming up with limited information.

 

Could someone please point me in the correct direction? Sorry if I’m overlooking an easily searchable topic, but I’ve searched for this info so many different ways.  
 

Thanks

Edited December 23, 2021 by Brtele (see edit history)

[1965rivgs]

1 hour ago, Brtele said:

I’ve been trying to find the float adjustment specifications online yesterday/today and coming up with limited information.

 

Could someone please point me in the correct direction? Sorry if I’m overlooking an easily searchable topic, but I’ve searched for this info so many different ways.  
 

Thanks

Hi Brandon,

  Do you have a factory shop manual? If not, that should be at the top of your wants list, especially as a "hands on" owner. Here `ya go:

Tom

 

[telriv]

Just as a caution & FYI.  Many 4GC's have diff. float settings between primary & secondary float adjustments. That's one reason to POSITIVELY identify the year, make, model & carb. number.

 

Tom T. 

[Brtele]

2 hours ago, telriv said:

Just as a caution & FYI.  Many 4GC's have diff. float settings between primary & secondary float adjustments. That's one reason to POSITIVELY identify the year, make, model & carb. number.

 

Tom T. 

Thanks Tom. This is really frustrating that the only way to identify my 4GC was an easily removable tag that was not provided with the carb when I purchased the car. 

Based in the above, I have no idea where the floats should be set to. 

i might be money/time ahead purchasing another carburetor that’s stamped or tagged with proper identification. Otherwise I could be chasing my tail for weeks trying to dial in the floats.

 

Let me know if I being too drastic too early or if there’s a good way to ID this carb without a tag.

 

 Thanks 

Edited December 12, 2021 by Brtele (see edit history)

[telriv]

Brandon,

 

    At this point I believe it would be in your best interest to just send your carb. to Jon  & have him identify it IF he can or just buy the proper carb. from him IF he has one.

 

Tom T.

[carbking]

1 hour ago, Brtele said:

Thanks Tom. This is really frustrating that the only way to identify my 4GC was an easily removable tag that was not provided with the carb when I purchased the car. 

Based in the above, I have no idea where the floats should be set to. 

Take a deep breath and look at the chart.

 

For Buick from 1957~1965 except for the vacuum assist float in 1959, ALL settings are within 1/32 of each other. 1/32 is comparable to 1/2 calibration size. You would have about the same change as driving up one (or down) of the Ozark hills here in Missouri that is 2000 feet high.

 

And its your own fault  for driving a 1965. Federal smog emissions began in 1968, and since the carburetor is considered to be part of the smog emission system, the carburetors had to be STAMPED with the identification number.

 

Just set the floats like would be correct for your model, and pretend you have a tag

 

Jon.

[1965rivgs]

1 hour ago, Brtele said:

Thanks Tom. This is really frustrating that the only way to identify my 4GC was an easily removable tag that was not provided with the carb when I purchased the car. 

Based in the above, I have no idea where the floats should be set to. 

i might be money/time ahead purchasing another carburetor that’s stamped or tagged with proper identification. Otherwise I could be chasing my tail for weeks trying to dial in the floats.

 

Let me know if I being too drastic too early or if there’s a good way to ID this carb without a tag.

 

 Thanks 

  The carb appears to me to be the correct `65 carb. As Jon suggests, use the settings for your application from the chart I provided.

Tom Mooney

[telriv]

Brandon,

 

    Just take Jon's advice on this as he has more knowledge about this than I will ever have.

 

Tom T.

[Brtele]

I got the car put back together and started the car.

 

Choke was adjusted and operated properly.

 

I set the idle rpm at 550 to start with.

 

i noticed quickly that the float to bowl gasket was wet with gas.  I’m thinking my float level is set too high showing the gas to fill too high in the carb?

I adjusted my pri/sec float level to 1-13/32 measuring from the gasket to the heel.

Accelerator pump worked well shooting gas in the primary section, but I have a slight hesitation - I’ll work that out later, but wanted to get this seepage issue worked out.

 

Any advice, guidance, questions or comments are welcome.

 

 

[Brtele]

I also tested the floats during disassembly by submerging in hot water to see if air bubbles would appear.

 

Both sets of floats passed the test.

[60FlatTop]

I am surprised to see phenolic floats in a 4GC. I would try to find out the original weight or buy new ones before going deeper into it.

 

When Q-jets were common I could just heft the float in my palm to tell if it was heavy. And it was common to find a bad one. You could have a sinker there.

 

Jon's comment of just pretending you have the number is bout the same as I would do. I might also just adjust to the mid-range of the spec and adjust from there. The top gasket can before disturbed quite a few times.

[EmTee]

55 minutes ago, 60FlatTop said:

I would try to find out the original weight or buy new ones before going deeper into it.

The one with the orange-ish gunk on it certainly looks suspect.  I think the material used has an 'open' cell structure.  If so, that junk will have permeated the stained area of the float.

[Brtele]

Prior to rebuild the primary floats’ level was much lower 1-20/32 (measured to heal). 
 

Also, both pri/sec float level measurements were quite different.

 

If I replace the floats, are there floats I should steer clear of?

 

Thanks,

[EmTee]

1 minute ago, Brtele said:

If I replace the floats, are there floats I should steer clear of?

Yes, the phenolic ones!  If you have a scale that you can use to weigh them (e.g., postal scale) it would be interesting to see how they compare to each other.  It seems like they should all have started out at the same weight given they were originally the same density and use the same float level setting.

[Brtele]

I’ll take the top back off and repeat the float adjustment but set the heel level measurement slightly higher (from the gasket). I’ll also measure the floats weight and report back.

[Brtele]

Just making sure I’m measuring and reading instructions correctly. I used the following picture/adjustment method to adjust the floats I have to 1-13/32. Please let me know if I’m off track.

[telriv]

Just my thoughts.

Those floats are JUNK!!!!   Get brass floats to replace them & then you should be OK from here out.

Call & ask Jon IF he has any to sell to you.

 

Tom T.

[Brtele]

1 hour ago, telriv said:

Just my thoughts.

Those floats are JUNK!!!!   Get brass floats to replace them & then you should be OK from here out.

Call & ask Jon IF he has any to sell to you.

 

Tom T.

Will do, thanks Tom

[Brtele]

Just a question regarding the float springs. Are they in there to “dampen” float movement over rough roads when the bowl fuel sloshes?  Just wondering about their purpose.

[Bloo]

If you must use plastic floats, never put old ones back in. They had a habit of sinking at about 80k miles. On some models, GM had you weighing them on a scale to determine if they could be re-used. If the car had already run long enough to need carb work though, what are the chances a used plastic float would hold up? Not good.

 

I agree to check with @carbking . Get brass if you can.

 

[Brtele]

Took the bowl cover back off and checked/measured the floats - I know I'm not supposed to use the plastic ones, but they appear to be working for the time being.  I'll continue to look for brass ones, but wanted to get the carb back together and see if I could get it running.  

 

Before I took the bowl cover off, I noticed the fuel connection fitting threads had a good amount of wet gas on them and decided to check the tightness of the fitting.  Holy crap, I didn't take this off during the cleaning procedure and believe it's lack of tightness was my issue.  I tightened it up using a "mechanic's tight" two finger tight and the carb is not leaking, but only "wicking" along the bowl cover gasket.  No drips.  

 

On to the next phase.

 

Thanks again for all the assistance.