Amazon: Rebuilding Zenith VN36 carburettor - any advice?

[fishyboy]

Hi all,
I intend to start rebuilding the Zenith VN36 carb from my 1966 131. I have the rebuild kit and a parts diagrams, but no instructions. My aim is to try a reduce fuel leaks from either the accelerator pump or between the car body and float chamber.

If anyone has any advice on rebuilding these cars it would be greatly appreciated.

Phil

[221Tom]

Hi Phil,

The Amazon Haynes manual and the B18A Volvo ‘Greenbook’ workshop manual give basic instructions to take the carb apart and re assemble it. If you talk to Burlen nicely, they might be willing to give you more detailed instructions or wear tolerances for components; I know that they do an S.U. Workshop manual, so may do one for Zenith.

Tom

[grumpydad]

Hi
well on the Austin A35 we have
it had a zenth on it and after several go at trying to rebuild it
it went in the bin we got a SU from a morris minor
and the car has been happy since

[Derek UK]

The VN36 is know as being a bit leaky down the side. Annoying but not a disaster. They come apart quite easily so dismantle and clean everything really well. If the butterfly spindle is loose in the body you have a problem. I don't know if they can be rebushed. It's a big jump to fit the later Stromberg with the twin downpipe manifold as you have to get a front exhaust pipe as well, but it is a really good update. About another 5 bhp and a bit more mpg if you can keep your foot out of it.

[fishyboy]

Hi all
Thanks for the input Tom, grumpydad and Derek.
Stripped the carbs down removing all the ancillaries. Throttle shaft looks and feel fine (the car has only done 16k miles). Gaskets were all in a pretty poor shape.
The cast parts have all gone in the sonic cleaner.
Hopefully I'll find time to get the rebuild done tomorrow.

Phil

[Derek UK]

Looks like you have the kit and are being very methodical. All should go well. If all of the stains don't come off in the cleaner, don't know what fluid you are using, cellulose thinners and a toothbrush may do the job. Good luck.

[fishyboy]

Hi al,
Carburetor body cleaned up really well in the ultrasonic cleaner (Photos). All the new parts went on without too much of a problem. Carburetor ancillaries (choke etc) all worked fine so I set the basic settings and put the carb on the car and she fired up first time. Set the idle to 700 and tweaked the mixture and ran the car for 20 mins.

After about 10 mins I started to notice the dreaded fuel leaks which appear to becoming from the joint between the float bowl and carb body. I used two paper gaskets here (one old and one new) because I could see an actual gap when I only used one gasket. I assumed two might seal the gap more effectively. Unfortunately there are no bolts to tighten the float bowl directly against the body (just the four vertical ones connecting the float top to the reservoir. I'll try with just one gasket but hard to see how that would help matters.

What about using some fuel-resistant Hylomar gasket sealant along the mating surface?

Any suggestions?

Phil

[fishyboy]

Hi all
Just found this image which shows a green gasket between the fuel bowl and the emulsion tube. Now when I disassembled the carb there was no gasket here so I didn’t look for one in the kit. Having looked again at the parts diagrams there is one in the kit I should have fitted. Will try in the morning.
Phil

[fishyboy]

Hi all
I added the gasket between the emulsion tube and the float bowl wall (Photo). Put the carb back on the car and ran for 20 mins. No leaks!

I'm not sure how long this gasket was missing before my rebuild, but I would guess many rears from the staining on the inlet manifold.

Fingers-crossed it stays leak free.
Phil

[WSU303]

I've just done the same job on my PV544 with Zenith carb. Previously it was leaking all over the exhaust manifold, covered in nearly 60 years of grime and gummed up petrol, and the car ran badly and didn't want to start.

Now after using one of the 'service' kits, it runs sweetly, starts better, and doesn't leak! Only downside is that it makes the rest of the engine bay look shabby But that's ok, that's the car's "look".

I didn't go down the ultrasonic route - instead just spent a few hours with wooden picks, toothbrushes, and lots of petrol and carb cleaner. Made sure to get into all the jets and passageways.

Thanks Phil and everyone else on this thread for describing the process - gave me the courage to crack on with mine