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Triumph TR3 - Float Bowl Bolt - New Moss Type

After trying everything to stop gas from leaking from the union between the float bowl arm and the bottom of the H6 carb on my '60 TR3A, I'm about to install the alternative bolt, cup washer and some new rubber seals from Moss. Does anyone know if this will necessitate a change to the float setting? Anyone installed one of these with good results? Any tips on making it work?

We just can't have gas leaking over the exhaust pipe. Lucky so far...

Thanks, all.

Bill Stagg
1960 TR3A
Bill Stagg

Bill: I had the same problem when I bought my TR.
I purchased a carb rebuild kit from TRF which I think contained those washers. I don't think I bought them from Moss, but I'll look at my invoice records and keep you posted.

If memory serves me correctly, these are sort of a flanged washer; one going on either side of the bowl arm with the flat side away from the arm.

In any case, haven't had a drop of a leak since...


Mike Gambordella


Thanks for the comments. Glad to hear you are leak free.

The bolt I have from Moss does not use the fiber washer (between the bolt and underside of the carb body). Both the standard style and the newer Moss bolt require the two flanged rubber seals for the float bowl arm.

Now that I have the new Moss bolt mounted, I can see that the float bowl sits as much as 1/8" higher than the one with the standard bolt. I'm wondering: will this require a change to the float valve tang (the one that is supposed to be 7/16" from the underside of the float bowl cover).

How's that beautiful 3 of yours running? Getting out much this summer?

Thanks, Mike.

Bill Stagg

Bill: The washers were not included w/ rebuild kit, bought separately from TRF. Part # SUAUC1534.
Don't think they require the fiber washer either.
Set my float forks at 7/16, never really noticed a different mounting height. Try it and see?

Running well thanks, 23-27 mpg pending amount of enthusiasim...Don't get out enough though.

Went to a show in CT awhile back, did a 1-1/2 hr interstate trip at 70-75 mph the whole way. Damn thing will do 90+ if I wanted to. (yes, I have) People look at us as if to say "that car goes that fast?"
Not something I'd want to do too often.

How's yours? Sounds like you are re-doing quite a bit of stuff.
Good luck w/ washers -

Mike Gambordella

I never have changed any of these washers, but if I understand correctly, all that could happen is the float bowl might sit a little higher. I don't think that would change the level of fuel in the bowl.

Tom - Bill's concern is that if the bowl sits higher, the float will sit higher and the float might not shut off the flow into the float bowl. Or the upper gas level may be higher in the bowl when the float shuts off the inlet valve.

This might mean that theere could be more flow into the carb in the venturi because the static pressure in the fuel feed in higher because the gal level static height is higher.

Bill - I'd get the job done and run it on the road. If it seems to be running rich (or richer than before) because it's mounted higher, you will want lean out the carb or carbs concerned by turning upwards on the lower brass hex nut(s) for this.

If it still seems too rich you may need to lower the needle in the piston that gets vacuumed up as you step on the throttle.

Don Elliott

Sorry Bill, before touching the richness settigs, you will want to bend the fork prongs that set the needle setting and the gas level in the bowl to put the fuel level back to where it was before. Then you should be OK.

Don Elliott

Wait a minute - this is a self-contained unit, so the float/forks and needle should do their job no matter where the bowl is mounted, no? To a point, anyway. The spacial relation between the float and the forks would remain the same, therefore fuel will come in, and given the correct setting, the needle should do it's job.
Like Don says, put 'em on and try it.

Ironically, my brass adjustment nuts wound up just about where the manual recommended for the initial setting after a rebuild.

Mike Gambordella

I get it now. Like your toilet would flush harder if the tank was high like the old water closets. In other words, the float should be adjusted with the chamber/piston out by looking down at the fuel around the jet. I have heard of this method but never used it. Old SU guys seem to think it's the only way, so there ya go. I forget the magic detail in this method, besides blowing down there to see the level better (fuel ripples).


That's exactly my concern. Randall says that the height of the float bowl relative to the carb body/jet shouldn't make any difference during operation of the engine because it is the vacuum that pulls the gas into the jet, and that shouldn't be changed. What could be affected is the amount of gas that would flow into (and out of the) the jet after shut off, because water/gas will seek its own level, and if you raise the level of the float bowl (as a unit), it may raise the resulting level of fuel in the jets. That may be why some folks have a strong gas odor after parking the car in the garage.

It seems that you can adjust for this by setting the float level lower (because the float bowl is now higher) or by raising the jet, as Don suggested. Because my float bowl is now approximately 3/16" higher than before, I'm thinking that lowering the float bowl is more feasible than raising the jet by 3/16". Not sure I have enough threads left on the jet adjustment screw.

Actually, Randall thinks the float bowl is now where it should be, given the carb body that I have. The only way to be sure seems to be a visual inspection of the carb, pulling the piston out after running the engine to get the gas flowing to its operating levels.

All this and more awaits in the garage today.

Thanks to all for the help!

Bill Stagg

UPDATE on Float Bowl Bolt and Levels

I installed the Moss float bowl hollow bolt (370-080) along with two rubber t-seals and one cupped metal washer. I pulled the rubber seals out of a rebuild kit I had laying around.

The unit still leaked, probably more than ever. I pulled it apart and noticed that the two rubber seals were a very loose fit around the hollow bolt. I then reused two old seals that fit much more snuggly around the bolt. Reinstalled the float bowl and, voila! No more leaking carburetor.

As for the different height of the float bowl relative to the carb body, it doesn't seem to make any difference. I'm using the standard 7/16" float setting. There is no flooding, no overflow of gas or any of that, either while running or after shutoff. This is the first time I've been able to pull the car into the garage after running without it smelling of raw gas for hours. What a change.

Thanks to everyone for the help.

Bill Stagg
Bill Stagg

Good to hear you have your leak fixed, and it still runs good. Now only your hands will smell like gas for a couple days.

Congrats! That must be welcome relief...
Gas 'er up, baby - you've got driving time to make up.
Mike Gambordella

This thread was discussed between 02/08/2004 and 11/08/2004

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