jw1955buick

Tuning ‘55 322 issues

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5 hours ago, 60FlatTop said:

 

When Detroit switched to downdraft carburetors the dealer network service manager requested lots of screws and adjustments for the carburetor. Lots of them right under the owner's nose just tempting him.

 

I would make sure I got it running on the idle circuit. You can do that by looking down the throat of the carb when it is running and making sure fuel isn't dribbling onto the throttle plates. Close the plates until that stops. If it doesn't stop, address the level issue. If it does stop at least you will be on the idle circuit and there's not much to scrutinizing that.

 

Wasn't there an initial drill bit size to use as a gauge to preset the throttle plate opening?

 

Actually, many of the older updraft carbs had significantly more adjustments than the downdraft carbs.

 

Virtually all updrafts would have:

 

(A) Idle mixture

(B) High speed mixture

(C) Curb idle (RPM)

 

These are the same basic adjustments found on most downdraft carbs.

 

Additionally, many updraft carbs had:

 

(D) throttle opening adjustment (yes, you could limit the opening of the throttle plate, Wouldn't that be useful when your 16-year-old got their license ;) )

(E) Dash adjustment for the auxiliary air valve.

 

And many (most?) late 1920's updrafts also had an adjustment on the amount of the accelerator pump shot.

 

Jon.

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From experience, there are some deposits that will NOT be removed by soaking.  They will have to be removed "mechanically", if at all.  BUT if they were in the idle and main system tubes which are on the "fuel side" of things, those deposits will restrict fuel flow and cause a lean condition (which will also prevent sufficient fuel getting into the venture for the engine to run.

 

Are there any small holes on top of the venture cluster?  IF their placement coincides with the smaller, solid brass tubes which go into the fuel side of things, then those air bleeds are calibration points in the fuel mixture curve for the idle system.  As they clog or are restricted, the idle circuit goes "rich".  Just spraying carb cleaner or blowing them out with air is not enough to get them cleaned out, from my experiences.  You might probe them with a very small wire to see if they are fully open.  The larger holes are for the main system, not affecting the idle mixture fuel curve.

 

In order to determine the size of the hole, you might try using a bent-wire spark plug gap gauge, to see which of the smaller sizes might or might of might not fit the hole.  With that size in mind, you can go to the hobby shop and get some twist drills of that size range.  Then gently probe/enlarge the restricted hole until you "get metal shavings".  KEY thing is to not enlarge the hole from the OEM size!  But clean it out just to that point and NO LARGER.

 

Now, I'm not fully aware of how that particular carb is designed.  But knowing how later Carter 2bbls and 4bbls were designed, I do know about, which is where my main knowledge is.  The air bleeds are part of the total fuel calibration curve of the carburetor, although the metering jets and such are what people generally think about when the subject of fuel curve is mentioned.

 

HOPE this might help,

NTX5467

Edited by NTX5467 (see edit history)
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It’s handy that I’m taking guitar lessons, I used a bit of that string to probe everything I could find, my choke pull off adjustments are getting better as I’m understanding the terminology in the shop manual, floats are now within a 16th of spec, that’s some stressful stuff bending those things 

I don’t know how to test the accelerator pump without installing it and running it which is fine, just takes time 

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23 minutes ago, jw1955buick said:

test the accelerator pump

Just fill the cavity with WD40 and push down on the loose pump.

Note that the float settings are done with the gasket OFF, which means that the floats will have to be removed to put the gasket back on.  I use appropriate size drills to set the floats instead of those supplied cardboard things.

Don't  swap or mix the main metering jets...the primary and secondary are not the same. Even if put back to where they were located, someone may have "messed with it" before (page 62 of service manual).

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41 minutes ago, jw1955buick said:

are getting better as I’m understanding the terminology in the shop manual

 

A couple of days ago I was talking about my friend, Mike, who passed away three years ago. He would use incorrect terms and be misunderstood. I would tell him "You can't call it that". He would always reply "Well, that's what "I" call it". But, Mike, it doesn't work that way.

 

What I wrote about updraft to downdraft was an untruth for illustrative purposes. I tried to make it lack credibility, make it bristle with adjusting screws to be irresistible.

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1 hour ago, 60FlatTop said:

I tried to make it lack credibility,

Bernie, apparently you succeeded beyond your wildest dreams.  As the owner of four vehicles with updrafts, I just chuckled....  🙂

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Silicone spray or lithium grease spray on the gaskets will assist removal - in case you need to pull apart a number of times.

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IF you plan on painting anything NEAR the place the silicone spray is deployed OR it might land, better get some "fisheye" additive for the paint being used.  Or a liquid to remove the silicone from the surfaces being painted.  Grease will work as well without the painting issues, I suspect.

 

NTX5467

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1 hour ago, NTX5467 said:

IF you plan on painting anything NEAR the place the silicone spray is deployed OR it might land, better get some "fisheye" additive for the paint being used.  Or a liquid to remove the silicone from the surfaces being painted. 

 

How true, that stuff is a horror story in body shops. Used car lots would use silicone spray to detail cars, then if that didn't work, they would send them to my shop. I had to buy a hot water  pressure washer with strong detergent suction hose to clean the cars, including the engine compartment to get paint work done without fisheyes in it AND other cars sitting nearby!😡

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