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Carbs - Adam Brown - 28-01-2020
We've been having some problems with our Chummy which I think considering it has a fuel pump (new) and the valves were recently attended to narrows our search for a cause down to the Carburetor.
It has the Zenith 22FZB which after talking to lots of people is identified as problematic.
My question is what are the alternatives? This one has been fiddled with to no avail and the bronze version seems the best way out (if one is findable). Are there any other like for like or similarly fitting alternatives out there that are more readily available?
RE: Carbs - Barry Townsend - 28-01-2020
I managed to find one on ebay and after some careful cleaning, setting up and treating it to a couple of brand new jets - problem solved. I was getting nowhere with the old ali one
RE: Carbs - Howard Wright - 28-01-2020
Hi Adam
Are you sure the ignition side is spot on?
It could be that your fuel pump is the cause of the problem. The 22FZ needle valve, float and butterfly actuators were designed for gravity feed, pressurising the assembly could result in flooding. The carb is relatively critical to float height.
However the Mazak material of the 22FZ doesn’t last well and post war Austin recommended fitting a Zenith 24T2 which was in use on several makes of tractor. The Bristol A7 club web site has a very good article on this carb and it’s fitment to early Sevens.
Of course you could always fit an SU. There are many threads in the forum on this mod.
Cheers
Howard
RE: Carbs - Barry Townsend - 28-01-2020
I managed to find a bronze one on ebay and after some careful cleaning, setting up and treating it to a couple of brand new jets - problem solved. I was getting nowhere with the old ali one
RE: Carbs - Adam Brown - 28-01-2020
Fairly sure. It has never previously been an issue and the fuel pump has been on the car for a very long time now. It did John O Groats to Lands End with it fitted in 2000.
I want to avoid an SU. Ideally I think the 22FZ is what I'd prefer but if I can't get one other avenues will need exploring.
The Bristol Club article is very good indeed.
RE: Carbs - Steve Jones - 28-01-2020
You don't say what the problems you're experiencing are, Adam. I wonder if your issues relate to using a fuel pump with your updraught Zenith? Dependant on what type of pump you're using and its location on the car it could be that fuel the pressure is too great for the carburettor and, if so, that can result in all sorts of issues from flooding to frothing in the float bowl. The FZ and FZB were quite basic carburettors with little to go wrong but were intended more for a gravity feed than pump. If your Chummy has a normal, scuttle, tank then try eliminating the pump all together with a simple pipe between tank and carb as original. If the tank is elsewhere and a pump is essential then look at fitting a pressure regulator so as to reduce the pressure of the fuel reaching the carb. The latter worked for me with a long standing problem although that was with an SU carburettor.
Steve
RE: Carbs - Chris KC - 28-01-2020
When you said 'carbs' Adam I thought this was going to be a dietary question! I could scarcely walk after the Cambridge club dinner on Friday.
As Steve suggests it would help to know a little more detail of what the problem is? Valves and pump still leave a few other possibilities.
RE: Carbs - jpsmit - 29-01-2020
As mentioned, more detail is always helpful, but, a persistent issue in the rest of my British Car World (and my lawn care world) is ethanol in the fuel. What fuel are you using? the carb can varnish up - I only use ethanol free fuel here in my MG (and lawn mower) and have had no issues since.
RE: Carbs - Adam Brown - 29-01-2020
The issue is that it doesn't like idle-ing at all when cold, and not that much when warm. It also runs fair well on a cold day but the minute it gets warmish after a while it starts to stutter horribly
I would rule out Fuel as that is changed regularly, the distributor is newly reconditioned, and as I've said we've done the valves. It always used to suffer horribly from overheating so a few years back it was all flushed out and a considerable amount of gunk removed from the block, which had previously blocked the water supply to all of the jacket around No.4 and most of No.3.
The fuel pump has been on it for years without ill affect. Understanding that the maizac on the carbs is often an issue that is where I've turned attention to.
RE: Carbs - Dave Mann - 29-01-2020