Hi,

I am at my wits end with my 1937 Austin 7 special.

It's a ruby engined car with a rebuilt distributor by the distributor doctor running with a zenith 26 vme downdraught carb and supalloy head and Dante manifolds

I have used the car a few times over the summer and it ran acceptably, although in my opinion too rich.

Recently it's been a pig to start and seems to constantly wet either number 2 or 4 plug. I bought some new jets and a new needle valve in the hope to get the car running sweeter by fitting some leaner jets.

I had it running yesterday and it only runs on all 4 cylinders with the choke partially closed.... I have returned the carb back to the spec it was in the summer and it still has the same problem.

I have cleaned the carb thoroughly, replaced the gaskets and did a compression check an all cyl are reading 110 psi.

After spending £40 on carb bits for the zenith, I am now considering changing it to a SU, I see people running with these vme carbs so they must work.

Interestingly I have another zenith carb which I believe is off a ford 8hp and it also seems to show similar characteristics running only with the choke

Could anyone give me any clues ?

Location: Suffolk

For a start tell us what size choke and jet's you have fitted. It sounds like you have fouled plugs through an over rich mixture, however are needing choke seems to indicate weak mixture, but this might just be that the engine is cold, it is hard to diagnose with out knowing all the facts, other than changing jets have you had anything apart since it was apparently running ok.

Location: Auckland NZ

your VME will likely either be a 20mm or 22mm choke - think the later is c1565 marked somewhere... so you ideally want the slightly smaller c1511 perhaps, not that its anything to do with the exact current problem!

Simon,

two things that have caused me similar issues for you to consider:

1. I have encountered a number of duff plugs recently - they appeared to be well known makes but are cr%p quality and I suspect were counterfeit.

2. I recently encountered what appeared to be overly rich mixture that was eventually proven to be caused by a sticky exhaust valve. The stem was covered in a thick tar-like substance that was preventing the valve from closing fully at lower revs. Once accelerating the increased inertia was sufficient to allow it to close.

Best of luck, these can be some of the most frustrating and time-consuming problems to sort.

Fresh petrol? Often overlooked. Including by me when my Ruby had been standing a while.

Simon, I was troubled with the usual Zenith problem of flooding carb and dribbling onto the exhaust. I decide to replace it with a SU. Ifitted a HS2 from a Mini making up a manifold converter to reduce down to apprx. 1 1/8". I use an AN needle and get a much smoother drive with a bit more torque, and no more leaks.
d to change

Location: Piddle Valley

Hi,

Thank you for your messages, I have been away all week with work unfortunately.

My carb is fitted with a 80 main, 57 compensation jet and 22 mm choke tube

I will drain the fuel and try a set of new plugs..... However I can't help but think the SU is a better option

Location: Suffolk

To confirm its a C1565 type carb by the way

Location: Suffolk