Projects The Hardscrabble Hop-Up; A 1940's Style 'T' RPU build

It's leaking the most out of the top of the float chamber. The fuel inlet needle valve is likely the culprit, but I think I might have some leaky gaskets. going to tear into it tonight, will post up what I find.

 

Got the carb apart...fuel inlet needle valve looks good and seems to be working properly; tried to force gas down the fuel line into the bowl and I couldn't overwhelm it with moderate pressure...float/fuel level in the bowl stays constant. Looks like the fuel line/fitting is dripping gas down onto the bowl...apparently the stock Model A style fitting isn't compatible.

While I'm at it, I'm going to put new gaskets in it & add some solder to the idle, intermediate, and hi-speed needles; they're a little worn. Hopefully that'll cure the idling issue.

 

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Yeah, pretty sure the stock fitting doesn't work. I'm using a compression fitting and 5/16 line. And nut

 

I'm thinking the compression fitting I've got is jacked up...the ferrule won't seat against the carb inlet...fitting gets tight before it's seated. Where'd you get your compression fitting?

 

Went to a few local parts stores/supply houses looking for the correct fuel fitting...found one I thought would work, but gas still dribbles out of the connection.

On a positive note, spent the evening hand lapping all float chamber mating surfaces and even with my crappy gaskets I've got it completely sealed. Still need to silver solder and true up one of the needles, and replace all gaskets - but the tedious work is behind me.

 

Try loosening and tightening like 5 or 6 times?

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Might give that a try. If you get a chance, can you post up a pic of your fitting?

 

i have never actually touched one of those winfield carbs but from the picture of it on the first page of this thread it looks like it requires a fitting that uses a copper washer. maybe?

 

With the help of my pal @Hitchhiker, looks like the fuel line leakage issue is figured out...apparently the ferrule is too small in diameter to compress to the 1/4" fuel line. Looks like I need to step up to 5/16" line and corresponding ferrule (presumably with a larger O.D. to better seal against the inlet casting).

In the mean time, I finished getting the mating surfaces trued up and needles silver soldered to the correct profile.


While I was at it, I bushed and drilled the air bleeders to the correct size; per Jim Brierley, the "B" size carb uses #28 bleeders - mine had #24. Luckily the fix was a simple as pressing in 3/16" brass tubing (.032" wall thickness) and drilling to the correct size (.1405").


Waiting on gaskets to arrive, then I'll slap it together and try to get it started.

 

Shit...I've got #30's in mine...

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Both the S and SR fuel inlets use female pipe thread. The were made to use a male pipe x compression fitting, male pipe x flare fitting, or male pipe x hose fitting.

 

That's what I was thinking mine was, but didn't want to say without going out to the garage and checking, and I've been too sick the past few days to drag myself out there.

 

Here's what I've been trying to use. Can you advise on the correct fitting & size line?

 

definitely different than what I am using, I never really thought about what thread style it was, I just dug around in a box of fittings I have and found whatever screwed in best.

 

can you post a picture of the "hole" it screws into?

 

Alright, my inlet has 1/2-20 UNF threads, so I need to ditch the -5AN fitting and get a proper Model A-Ford V8 inverted flare fitting & ferrule. Should solve the problem. I believe the vertical inlets might be the ones that use NPT...

In the mean time, I put it back together with the old gasket set & tested the inlet valve and inlet-to-bowl cover gasket seal. No leaks! Also cleaned up the hardware and brass bits.

As soon as the new gasket set is here, I'll go through it one last time & get the float level set.

 

Oh wow...excellent thread!!! Very cool!

 

Nice! I was pretty sure it was 12-20 but wasn't sure of the UNF stuff, as I still am not sure I understand all that, and didn't want to advise it as I wasn't sure.

 

Thanks man!

Yeah 1/2" diameter (major) with 20 threads per inch. UNF, or Unified National Fine is just the standard; has something to do with the thread profile (60* IIRC). Pretty typical thread, but it gets confusing because there's some funky stuff out there, especially with early pieces...British Standard, Whitworth, etc.

Pipe thread (NPT) is a different animal as well - its threads are tapered.

My issue is that I've been trying to seal it with an AN fitting...it has the right threads - wrong flare (doh!)

 

Remember AN translates to Army-Navy Standard, and was a product of the military trying to standardize all the defence manufactures during WWII. It wasn't fully harmonized until 1943.

You can pretty much assume that anything pre-war is incompatible with anything AN.

 

Rainer Hooker. Great info. Mechanical history sleuth!

 

never had one of these carbs in my hands before, is there a power valve or a accelerate pump in them??

 

The SR's (like mine) have a diaphragm that is supposed to act like a pump...I've heard they never really worked quite right, so most guys just screw the needle for it all the way down (richest setting).

Not much to update; still waiting on a few bits & pieces to get the carb finished. A while back I picked up another B sized intake and stashed it away...at one time thought about welding it up to make it a 2-carb intake as the casting is MUCH rougher than my other one (shown on the 1st page). Don't think I'll end up doing that, so I decided to start polishing it. Thinking it might make a good backup with a Stromberg 97 adapted to it. Chrome 97 and a polished intake would look yummy.

Smoothing the casting and polishing inside those tiny letters is a chore!

 

The fitting for your carb is probably JIC not AN. They look the same but have a different angle on the flared end. One is 37 one is 45. Both are available in brass.

And yes it is a 60 degree thread, whitworth is 55 degree but that is pretty much english stuff even pre WW1.

Try following with vintage rifles if ya wanna see some odd ball threads and pitches.

 

I have or have had several of fuel inlets with the side inlet. They have all been 1/4 pipe some one must have modified that inlet. I also have dual manifold castings. As to the diaphram pump most just turned bottom cover 1 hole to close it off. It was strictly a marketing gimmick as most other carbs were coming out with the pumps and the people that controlled the marketing of Winfield demanded that he produce a carb with a pump. I have read where it was stated he never liked the carb. If a S is tuned properly there is no need for a pump, they don't stumble!

 

how the hell are you polishing in between those letters?

 

Hey Bill, that's what I initially suspected as well, but the math doesn't seem to work for tapping 1/2-20 over 1/4 NPT; the TPI and major/minor measurements overlap too much. This one appears to use the Model A/early V8 fuel fitting & ferrule. My inlet definitely has a shoulder machined inside for a ferrule.
Don't know anything about it's history, but the throttle body, fuel bowl, bowl cover, and inlet all appear to be of the same vintage. The float bowl is stamped "G" and the cover is stamped "C" - indicating it was designed for gravity feed with the "C" float inlet seat/needle, which matches period literature. Perhaps Winfield had 1/2-20 inlets available as an option for Model A applications?

Everything you see there was done with various files and fine pumice & cloth (by hand). I have a decent collection of jeweler's files that really get into the nooks & crannies of those letters; it's just a super-tedious job! Still have a ton of work to do on it to make it presentable...

 

I have two of the side inlet tops. One looks to be 1/4 NPT while the other is 1/8 NPT. I don't know if a single intake could handle the weight of another carb. They weight almost 5 pounds each.

 

love following this build! The quality is outstanding and attention to detail is great! Keep at it!

 

Mine is 1/2-20 as well. I can check my others.

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