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Thread: problem just rebuilt SU carbs

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    Yoda
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    problem just rebuilt SU carbs

    I hate these cars why do I work on them. I just rebuilt these SU carbs and the front carb has fuel dripping fast out of the lower jet assembly when I try and start the car. At first I thought it was the lager cork gasket, but I do not think so now. The kits are new and I got them from Joe C.--- I took out the assembly and everything looked correct. The grand washers are new. How could it leak like that right at the bottom of the jet assembly soooo much; it is a fast drip! Any suggestions to fix, adjust, or change in the jet assembly. The engine probably has about 3 hours on it.
    steve

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    Great Pumpkin TR3driver's Avatar
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    Re: problem just rebuilt SU carbs

    Remove the jet and inspect it. Originals used a blind hole in the center, but I've seen reproductions that have the jet drilled through, then a plug put in that also retains the clevis for the choke linkage. Those plugs often leak. You can try sealing it up, but I just replace them. If necessary, use the old jet until the new one comes in.

    If you're using the (original type) cork gland washers, I suggest changing them for modern nitrile O-rings. Cork being a natural product frequently has flaws in it that can cause a leak. The nitrile will also last much longer.

    While the jet is out, check the surface for any imperfections as well. The surface should be shiny, not dull. (A dull surface won't be the cause of your leak, but does make choke operation much harder, and accelerate wear of the gland.)

    Make sure the fuel is actually coming from the jet assembly, and not running down from the float bowl mount.

    Everything else I can think of involves improper assembly. Oh yeah, suggest a more positive attitude. If you've ever rebuilt a Rochester Quadrajet or Carter Thermoquad, you'll see that SU carbs are a miracle of simplicity
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Yoda
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    Re: problem just rebuilt SU carbs

    Thanks Randall makes good sense. I guess I do not know what really makes the assembly seal if not the gland washers. The ones I used were like a synthetic cork. I can never get those O rings to seal, but I probably had the wrong ones. Those copper washers that fit on the top half of the jet and the thin one that goes on the lower part of the jet, are they for sealing fuel back or messing parts? I thought--- I saw once how the thin gasket was a shim to bring the lower assembly to the correct height, but cannot find the info? I mean I could put another one on to raise the lower jet up or something, and yes I have seen those jets you mentioned with like an insert and I will look for that. Think I will take it apart again tonight.

    I do need an attitude adjustment also, really I do—I should be more grateful for my shop and the stuff I get to do. Plus I rebuilt a 3 barrel carburetor on 1985 Honda.

    thanks Steve

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    Jedi Knight
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    Re: problem just rebuilt SU carbs

    I do not know if it will help your situation. I have always been told to soak the cork in oil overnight.
    Charley
    Charley
    1962 TR4
    1963 TR4
    1959 TR3A A work in progress.

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    Yoda
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    Re: problem just rebuilt SU carbs

    I do that too. I took the assembly back off and cannot see a problem. The only thing maybe is the little brass washer did let the lower assembly fit a little low, but I do not know if that matters, yet I added another very thin copper washer. I am going to replace the big cork gasket while the assembly is removed and I have that soaking in oil, but again the other one is new and looks good.

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    Yoda poolboy's Avatar
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    Re: problem just rebuilt SU carbs

    See if Joe has any tips for you.
    DRIVE 'EM IF YOU GOT 'EM

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    Yoda
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    Re: problem just rebuilt SU carbs

    Good idea Poolboy, I often forget the obvious.

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    Yoda poolboy's Avatar
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    Re: problem just rebuilt SU carbs

    I was taking to Joe today. He was asking for feedback or reports on some of his components so I bet he'd be interested in what you have to say.
    DRIVE 'EM IF YOU GOT 'EM

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    Re: problem just rebuilt SU carbs

    Tom Bryant sells teflon o-rings for very reasonable prices. His blog is also a wealth of information on rebuilding SU carburetors.

    https://thosbryant.wordpress.com/faqs/
    60 TR3A TS66043

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    Re: problem just rebuilt SU carbs

    Good Day! Just a few words of encouragement (I hope); I just resealed the carbs including float bowls on my TR3, first time in them or any carburetor that I can remember. Went well and after 2 or 3 short runs, no leaks, minimal fuel smell (if any). I stumbled my way thru, ordered parts as I went along (not very cost effective-shipping) but I am pleased and feel a simple confidence from the task. Looks like a dark tunnel at the beginning but as progress is made, daylight! I agree with other comments regarding the simplicity, impressive!

    Best, JS

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    Yoda
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    Re: problem just rebuilt SU carbs

    It took me some time, but I did figure it out. I did not tighten up the screw tight enough on the needle in the piston and it moved up and down. I am getting better at taking assembly’s apart. It was a difficult one for me.

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    Jedi Knight
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    Re: problem just rebuilt SU carbs

    Yes, there are a hundred or more ways to assemble them wrong and only one way to assemble them right. This keeps us on our toes.
    Just don't give up.
    Charley
    1962 TR4
    1963 TR4
    1959 TR3A A work in progress.

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    Re: problem just rebuilt SU carbs

    Bravo! I disassembled/assembled mine 2 - 3 times during the process. Good experience to have and unbelievable resources on this forum and other sites.

    Best,

    JS

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    Yoda CJD's Avatar
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    Re: problem just rebuilt SU carbs

    Glad you solved it! I think Iíll have to rebuild mine soon. Funny, they were tight as a drum for 2 years, but starting to seep a bit lately.

    Another leak I took on today was that original shut-off valve. It was dry for a year...then leaked when turned on for a second year...and this year is started dripping constantly. The only direction it positively stopped the fuel from going is to the engine! So, the long term study says cork is only a temporary gas seal...and this includes carbs too. The goal for today was to get the valve removed and the line to it plugged. I got one of every size plug I could find in the shop and broke the fitting loose. Within a minute my latex gloves were melted to shreds, a gallon of fuel missed the catch bowl and was all over the floor, and I was stuck holding the fuel in with my bare finger. Yep, the Dutch boy with his finger in the dyke, but no one to call for help! I finally managed to stuff part of one plug precariously into the line and run for a hose. I should have thought of the hose to begin with...but I am slow these winter days. In the end all is well, except I have every fan in the house drying the several gallons of gas out of the garage and I smell like a gas pump.

    My plan is to re-engineer the piston inside the valve to accept an o-ring seal. An o-ring should last a couple decades instead of just a couple years. Iíll post the results...

    Anyway, just rambling...get back to work, Steve. I am still living through your project!
    John

    1955 TR2

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    Yoda
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    Re: problem just rebuilt SU carbs

    Yeah I met that Dutch boy twice, once 20 years ago and last year; he is very, very scary, guy, and now I carry a rubber/knofreem cork and one of those ones I fabed up out of 2 different size weed eater fuel line pieces with one inside the other to hopefully keep that Dutch boy away. The O ring is a good idea. If I had a metal lath, I would have probably gone that way. However, the weed eater fuel line looked good and is holding so far.

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    Yoda glemon's Avatar
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    Re: problem just rebuilt SU carbs

    Quote Originally Posted by charleyf View Post
    Yes, there are a hundred or more ways to assemble them wrong and only one way to assemble them right. This keeps us on our toes.
    Just don't give up.
    I know most of you know this, but in the event it might be of use to somebody...
    When blessed with a pair of parts to work on (carbs, suspension, and brakes come to mind) do one assembly at a time if at all possible, that way you can use the intact part as a reference. I figured this out when I was young, but it is more and more useful as I get old and sequences of bolts, spacers, washers, seals and such often slips from my mind faster and easier than the assembly comes apart.

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    Great Pumpkin TR3driver's Avatar
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    Re: problem just rebuilt SU carbs

    Quote Originally Posted by sp53 View Post
    Yeah I met that Dutch boy twice, once 20 years ago and last year; he is very, very scary, guy, and now I carry a rubber/knofreem cork and one of those ones I fabed up out of 2 different size weed eater fuel line pieces with one inside the other to hopefully keep that Dutch boy away. The O ring is a good idea. If I had a metal lath, I would have probably gone that way. However, the weed eater fuel line looked good and is holding so far.
    I did much the same thing, but it was just nitrile (ethanol-safe) automotive fuel line. It did start weeping a bit after 10 years or so, but just took a tiny fraction of a turn on the adjustment to stop that.

    Yeah, cork doesn't last very long. I strongly suspect the original stuff was better than what we get today; but still didn't last nearly as well as more modern materials. When I was commuting to work in the TR3, cork in the gland seals would only last about a year before it started weeping. I got pretty good at just dropping the jet housing to change those seals (without removing the carb) but it was still a PITA. But ordinary nitrile O-rings work great.

    While we're on the topic of better materials, anyone using Delrin for throttle shaft bushings? Hadn't occurred to me, but the rebuild kit for the Ferguson tractor came with Delrin instead of brass. Seems to be working OK, although it has other issues that I haven't run to ground yet.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Yoda CJD's Avatar
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    Re: problem just rebuilt SU carbs

    Interesting. Are the inserts solid Delrin or a Delrin insert in the middle of the larger brass insert?
    John

    1955 TR2

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    Great Pumpkin TR3driver's Avatar
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    Re: problem just rebuilt SU carbs

    Just Delrin. Same size and shape as the standard insert (although a bit longer than necessary). The kit came without instructions, but the carb (an updraft Zenith IIRC) already had (badly worn) brass bushings in it, so I just tapped them out and pushed the new Delrin ones into place and trimmed them to length. Never thought to take photos, although I definitely should have.

    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Luke Skywalker
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    Re: problem just rebuilt SU carbs

    Who sells the Delrin bushings?

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