TR6 TR6 Leaky Carbs

[mrv8q]

Hello, listers, so my next post on my "new" 74 TR6 is on the leaky rear carb. Now that I've figured out how to attach a pic, it's leaking from where the white paper towel is stuffed into a brass hole. I'm not familiar at all w/ ZS carbs. Anything to look at before I send 'em out for another rebuild?

Also, can someone, at their convenience, either post a pic, or point me to a clear pic of the vacuum tube routing of these carbs? There's lots of small tubing in the bay, not hooked up. I don't have a Haynes yet for this car; there's a thrashed TR4 book in the trunk, go figure. Many more questions to come!

 

[RomanH]

Kevin,
That hole is the float bowel vent. If you are getting fuel out of it there are at least 2 things you have to do. The first is you need to adjust the float level for that carb. Presantly it is set too high or the needle valve is sticking or the float actually took on fuel and sank. Second you need to make sure that the vent valve is operating properly and adjusted correctly. The vent valve should be closed at idle IIRC and open with the throttle. Take a hose and cover that hole then blow into it to check the operation. You should be able to easily find the screw that adjusts the lever.

 

[AltaKnight]

Kevin....
Look at the moss motors website for more info on the vacuum hose routing. It's got pretty good drawings which will help you locate the right places for that plumbing.
There is a small hose comes off the bottom of one of your carbs which goes to the vacuum retard on the distributor via a switch on the top hose, if that's not connected you have a large air leak and will have trouble with mixture and idle speed.
Of course, the gas leaking out the vent indicates you've got other issues to deal with, most likely a stuck or leaking float needle valve.

 

[mrv8q]

Thanks, gentlemen, I'm awaiting the Moss catalog, and I've got to scare up a Haynes; more to come!

 

[mrv8q]

While I await my Bentley manual, another dumb question... Can you adjust the float level while the carbs are on the car; that is, does the bottom of the carb unscrew and pull down without springs and such flying everywhere? Thanks in advance!

 

[AltaKnight]

The carbs come off the inlet manifold fairly easily via 4 nuts.
Make sure you note or photograph how the throttle linkage is assembled before you start to aid in reassembly.
There's not much you can do to the carbs in situ, don't bother trying.
Take the carb off and invert it, remove 6 screws (there are 2 different lengths make note where they go back) and the float bowl lifts off. You can then inspect the floats for signs of any gas inside them and you can remove the needle valve to clean or replace it.
If you replace it you may have to reset the float height by bending the tang (gently) that presses on the needle valve since not all valves are the same height.
I had a lot of trouble re-setting the float height with the car wanting to run rich and eventually got pretty good at removing those 6 screws and adjusting the float height in situ. After a couple of trial and error adjustments I got it spot on.
The mixture itself is adjusted seperately (after you've corrected the flooding problem) with a special allen wrench through the top of the carb after removing the large plastic damper nut. The wrench is special since it holds the air piston still while turning/adjusting the needle height, if you don't use the right toll you will tear the diaphragm inside.
Good luck.

 

[mrv8q]

Thanks, Graham, you're a very capable Bentley substitute in the meantime! One more question; do you use ATF in the damper? I initially put in SU oil, (30W?), because they were bone dry, but read somewhere about the ATF...also, is that special allen wrench available? As you can see, I've a lot to learn.... again, many thanks!

 

[AltaKnight]

The special wrench is available at TRF or Moss motors etc for a few Dollars. If you have a British car (or maybe an import) repair shop locally they might have one also, you will most definitely need it.
I just use engine oil in the dampers, 20/30 or whatever, it doesn't matter except that lighter oil is more likely to leak past old o-rings and disappear more quickly than thicker oil.
The damper oil slows down the rising of the air valve when the throttle is poked thereby momentarily enriching the mixture so the engine doesn't bog down or stall. It's the same but opposite effect to the accelerator pump on a conventional American carb. Thicker oil means a richer mixture for a bit longer than thin oil.

 

[prb51]

I use ATF in the winter months as a 30 weight is a bit much, to slow, when cold. 20/30 fine in the summer months.

 

[Tinster]

Kevin:

You also might want to contact Jeff Palya.

https://www.paltech1.com/

His speciality is restoration of Stromberg
carbs. The carbs on my 1969 TR6 were so messed
up a Brit car expert told me to send them off
for restorarion. My intake manifold was also
buggered up by the previous owner and I sent
it off to Jeff as well.

Many folks here have used Jeff and his finished
product are carbs that are functional and drop dead
beautiful. Jeff is also very helpful during the
install of his carbs. They arrive pretty much bolt
on and fire it up.

Send Jeff a few photos by e-mail, he will answer
you back in a day or so. He is a good guy to work with.

Dale in Bayamon, PR

 

[danstr6]

I had my Zenith Strombergs rebuilt by Joe Curto in NYC a couple of years ago. He did a fantastic job and was very reasonable. This is his speality. He truly knows his stuff. You can check out his web site at https://www.joecurto.com.



"Knowledge is power, but everybody knows that."