1930 Cadillac V-16 Carburetor

[carbdoc]

I am humbled that I must do this, but I need some (ahem) carburetor advice.

 

I have restored the dual carburetors for a 1930 Cadillac V-16, but I cant get the right-hand carburetor to stop leadking.



A little background about me:  I have been building Cadillac (Johnson) carburetors (among many other brands) for over 30 years.  I was too young and dumb to know what I was getting into back then, and I'm too old and stubborn to stop doing it now.

So:  I have restored a pair of Johnson Carburetors for a 1930 V-16 Cadillac . . . and I have encountered a problem with one of these carbs.  The model number of the carburetor in question is R7-1017, which is stamped into the side of the mounting flange. 

When I apply the tiniest bit of fluid pressure to this carburetor (far less than 1 psi), the test fluid (odorless mineral spirits) gushes past the needle and seat, courses up through the discharge nozzle and runs out of the fixed air intake at the bottom in a small stream.  In other words, the bowl floods.

Yes, I am aware that the car uses a vacuum tank which applies only gravitational pressure to the carburetors . . . but, if a gentle squeeze on a test bottle  is "too much pressure", then why does the left-hand carb not have this problem (along with the other updraft gravity-fed carburetors that I build?).

Here is my checklist of things I have done to correct this, but to no avail:

-- Used a total of three different needle and seat sets (with pull clips) supplied by Straight-Eight.

-- Tested with vacuum between needle seated in seat and fuel inlet fitting.  Tested good.

-- Performed same test with needle seat plugged with latex plug in place of the needle.  Tested good.

-- Replaced float hinge pins with new 3/32" polished brass pins.

-- Inspected factory articulated float hinge for wear and/or "going over center".  Tested good.

-- Replaced float with Nitrophyl reproduction from Straight-Eight and adjusted to slightly lower than 7/16" factory specification.  Checked for any sort of binding by the float or its hinge within the bowl.  None found, float is clearly moving from open to closed and binding with nothing within the bowl.

-- Resealed discharge nozzle and plug in bottom of it twice.

-- Thoroughly sealed bowl bottom gaskets and nut.  No leakage from there, only from the discharge nozzle.

-- You should be aware that I always tear-down the carburetors that I build to the least component (leaving "no stone unturned"), and then clean them thoroughly with Berryman's B-12 Chemtool carb cleaner. Before reassembly.  These particular carburetors were restored cosmetically, so they received even closer attention.

Has anyone else encountered such a situation and, if so, how did you address it?  I am at a loss.

Jeff Dreibus

[Matt Harwood]

Paging @edinmass, please pick up the white courtesy phone.

[carbdoc]

24 minutes ago, Matt Harwood said:

Paging @edinmass, please pick up the white courtesy phone.

Thanks, Matt.

 

Jeff

[edinmass]

The list for problems is endless........

 

Bent lower fuel bowl

cracked main body

nozzle gasket leaking

bowl gasket leaking lower.......if upper is leaking you have other issues

stuck float/clearance issues

bad hinge

modified hinge

incorrect needle and seat

 

You need to bench test it, while looking at the carb from underneath, and actually see if the float is dumping out the nozzle........

Most of the parts available are poorly manufactured.........and I do NOT use them. I make my own stuff for them as needed.......

Many of the parts are incorrectly calibrated..............

 

I have flown out to multiple garages fixing these things after others have had issues with shops or rebuilders. They are NOT easy to deal with, and I NEVER do them without the car on hand. Too many changes with fuel delivery systems, fuel pumps, modified vacuum tanks, ect. 

 

For such a great car, the carbs are absolutely trash. I have probably done over 200 of them in the last 40 plus years. Some have kicked my ass.......PM sent with my phone number....Ed

Edited November 25, 2022 by edinmass (see edit history)

[Oldtech]

One easy suggestion. Try it without the float clip.  I know nothing about Johnson carbs but I have had carb kits that came with clips but the clip prevented the needle valve from closing quite all the way. 

[edinmass]

I’ll lay this one on you.  NO ONE makes a correct needle and seat. NO ONE. It’s a statement of fact. 
 

 

Please post photos of the new and old parts side by side……..

Edited November 26, 2022 by edinmass (see edit history)

[carbdoc]

Edinmass,

 

Thanks for the reply.  The test fluid is definitely coming out of the discharge nozzle and nowhere else.  I have tested it by plugging the needle seat and applying vacuum to the fuel inlet.  That would seem to rule out a cracked casting at the point of the inlet system. 

Using a new rectangular gasket and fiber washer each time, I have now resealed the nozzle to the main body twice (ditto the brass plug in the bottom of the nozzle).  

There is no wear in the hinge, and I have replaced the brass pins retaining it to the bracket (as I always do).  It is definitely not going over-center as I have seen extremely worn hinges do.

As others have suggested, I will  try it without the needle pull clip and see how it goes.  I will also try switching the floats between the two carburetors.

I, too, used to fabricate my own parts for these carbs, but then I found that most of the Straight-Eight components seem to work without any problem . . . until now. 

 

Jeff

Edited November 26, 2022 by carbdoc (see edit history)

[Johan Boltendal]

Hi Jeff , interesting comment from Chris about the pice of wood the driveres carried, what might help, is lessening the movement of the float, I once found an old float with a triangular thin steel wire inserted at at the lower end of the float, height about a 1/8 of an inch.

this way not allowing the float to go down to the float housing bottom all the way. normally it wont go that far at a regular fuel supply, but under certain circumstances it happens. 

The lesser movement of the float will give a shorter movememt of the needle, staying more centered,  as well as lesser movement of the hinge. Have used this float stop all the time since I found this

and have done a few carbs over the years. But then you may already have this in place . 

Not using the clip can lead to a stuck needle, if the float rests at the bottom , allowing the hinge to let it fall side ways. 

Happens if you forget to open the shut off valve at the vacuum tank , how I know....... Did you check the free movement of the new float when closed towards the center tube of the carb, 

Found some that got stuck due to too small a cap between float an carb tube. Sandpaper will solve that issue. 

Good luck and please let us know if and how you solved this issue. Johan

[carbdoc]

Thanks, Johan.  I can see this update working if the hinge is sufficiently worn that it will "go over center" when the float bottoms in the bowl, but I inverted the bowl on the center "post" while testing (as I usually do) so that I could see what happens with the hinge when the float is fully open.  No binding occurred.  I may still try your suggestion, albeit with a lighter-weight material than steel.

 

Jeff

Edited November 26, 2022 by carbdoc (see edit history)