Carb confusion!

[Grin-a-lot]

I've got a DCOE 40 carbs and while rebuilding it I noticed these small holes.



One is hollow so that you can see the idle air/fuel screw and the other is blocked.  I shouldve thought that both barrels would be the same.  What makes me curious is that i've always struggled to get the car tuned properly and on a couple of cylinders it always seems to run a bit rich despite what you do.

I don't suppose anyone can shed any light on this?  I've got them off the car at the moment so may pop down to a garage if no-body here knows.

Ta muchly...

['The Gaffer']

How strange, I have looked at a few online pics and dont see those holes on other carbs. These seem to be behind the gaskets?

Not even shown on parts diagram, a mystery maybe.

[Grin-a-lot]

It's the same as the overhaul kit; the holes don't feature at all.  I'm suspicious that 1 barrel on each carb is like that and 2 cylinders are hard to tune because the screw has almost no effect.  On the plus side the rebuild seems to have gone well!

[Grin-a-lot]

Right, it turns out that the holes are idling/progression holes and the blockage is a lead plug designed to block it.  What I've yet to figure out is why one side has it, why one doesn't and what I need to do about it.

The plot thickens...

[Grin-a-lot]

I think we have a winner.  The lead plugs are there to be drilled should its associated channel require cleaning/flushing.  Why it has gone missing remains to be seen but explains why the idle screw does nothing - it's essentially a big air leak on the idle circuit.

So the plan is to bung it with some solder wire when I get back to home, refit and retune the carbs and enjoy many miles of improved fuel economy and revel in correct fuelling loveliness!

['The Gaffer']

I think we have a winner.  The lead plugs are there to be drilled should its associated channel require cleaning/flushing.  Why it has gone missing remains to be seen but explains why the idle screw does nothing - it's essentially a big air leak on the idle circuit.

So the plan is to bung it with some solder wire when I get back to home, refit and retune the carbs and enjoy many miles of improved fuel economy and revel in correct fuelling loveliness!

Result

[David H]

fair play to you!