Series 3 Zenith 361V rebuild howto

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Castor

Castor

Trainee maniac
Posts
669
Location
Ebley, Glos.
Evening all,

I've just taken a misbehaving Zenith "Made in UK" off my 83 109 shed, and I have ordered a rebuild kit offa da net. I have probably overhauled a hundred or more carbs over the past fifty years, but never a 361V. New territory for me

Can anyone point me to a good "how to overhaul and recommission your 361V" article/document etc?
 
Its not hard honestly, you dont need a guide. Just take photos as you go and clean all orifices with 30psi and carb cleaner. Check needles are not shagged and float not taking on fuel. Absolutely the most crucial thing on a zenith is to lap the top and bottom mating surfaces. Get a completely flat surface like a kitchen work top, mdf sheet or glass pane. Stick some 1200 grit on and spray with light oil of choice. Do both mating surfaces in even strokes until you get a both flat. Zeniths warp badly.
Check accelerator pump is working ok too, nice jet of fuel when primed.
 
Thanks for that....
It's asking a lot for a casting like that to stay flat - but mine doesn't seem too bad. The principal problem is it's had water through it and what looks like a significant quantity of very finely ground Iraqi desert.....
 
Re: Flatting carb edges: You'd be surprised how bad it is. It's a matter of 10 minutes to clean it up, and well worth the effort.

As far as the water and dust I'd think about dipping it if you can get it. Here in the States you can buy a 1-gallon paint can 3/4 filled with solvent and a dipping basket for not a lot of money. This stuff is an agressive solvent for all sorts of carburettor crud. A dip and soak in that will shift the most persistent garbage - i did one that was full of tar and varnish from long-expired fuel and it came out clean and worked well.

Other than that, Ron is right - just be methodical, clean and blow out all the passages and it will work just fine. I rather like the Zenith myself - it's a good carb when the castings are stress-relieved and flattened to seal properly.

Alan
 
I'm wondering if a warped casting base might be my problem, or if it's simply some internal gummed-uppedness, or if it's something else entirely.

42k mile from new original Zenith on very late 3-brg 2.25 in 1980 88". The car'd sat around for about 14yrs, with a couple of years on the road (but minimal mileage) a few years back. To start with, it would not idle at all. I took the idle air screw out completely, and the groove was blocked up. Cleaned that, put it back in. It's now idling happily, but if I adjust the throttle stop so the idle speed is any less than "quite fast" (at a guess, about 1200rpm), it dies a good proportion of the time when you first come to a stop. I've put ~8-900 miles on this year, probably more than the entire rest of the century.

It did have EGR on - long disconnected from the exhaust manifold, which has been changed and has no boss. The union for the EGR on the carb's been welded up and is air-tight. It's on powerspark ignition, all-new HT.
 
The way to tell if you have a warped casting is simple - wind the mixture screw all the way in. if the car dies, the O-ring is sealing properly between the upper and lower halves (which is a part of the warping problem).

This sounds like another carb that could use a dip - or at a minimum a good bit of carb cleaner shoved throufgh the passages.You've likely got varnish or some sort of crud in the idle circuit.

I just ran into a similar problem on my Series I 86 - it would idle fine, then wouldn't idle at all. Reemoving and blowing out the passage behind the mixture needle and the idle jet seems to have cured it.
 
I like the dip can approach, but alas no such thing here in the UK.
Years back we used a mix of xylene, toluene and dichloromethane, ether and aviation spirit and ran the engine on that for a few minutes. Amazing stuff came out of the back.....

So yes, in my case it's the squeaky clean and blow through approach - let's see what happens.
 
Well I stripped and rebuilt the carb. And the squeaky clean and blow through approach works fine! We now have a carb that behaves...

What a ridiculously overcomplicated pile of cak the Solex/Zenith is though - give me an SU any day.

Thanks for the input, team. :)
 
Xylene and toluene are pretty carcinogenic! But good solvents : ) glad its working ok. I had to ditch mine as it had a worn thread somehow on mix screw. The weber 34ich I replaced it with was new and worked very well, should anyone want to change a zenith.
 
ciderman said:
Get the weber 34ich- apart from very occasional icing, it is very simple and far far better than the zenith.
Click to expand...

Not really - lower top-end and general power - throat is a lot smaller. it's a good 'economy" carburettor. I have one of each, myself, on different cars - and they each have their virtues. In any case, this is not the place for this argument, methinks...
 
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