Webers leaking at O ring mounts

[oldchieft]

From past posts

lotus-carbs-f40/help-with-webers-t31195.html#p218433

Another way to sort levels

Jon the Chief

[Hawksfield]

Hi

The method I use to set float levels on 40DCOE 51 carbs

[elanner]

Tim,

OK, thanks. So the "+4.5mm" seems to be a typo for "+/- 0.5mm"

I set my fuel level to 25-26mm last year (with the top cover on) so it's probably still a little high. Perhaps that explains my current theory of some occasional leakage from the starter air intake - I park the car in a deep underground garage so the fuel level is definitely unstable while driving up & down. I'll tweak it again next season.

Nick

[simonknee]

Keith Franck did a lot (like a one man R&D departments worth) of work to show that the Weber spec of 29mm is not optimal at all and results in hesitation on acceleration. The 25mm spec comes from his excellent work. Set it at 29mm and you may alleviate your symptoms (yes your steep incline may be to blame. However you may also ruin your drive!

edit: although perhaps the 29 works from a different datum - all that cover on, cover off stuff. Just go from the top of the internal bit you see when you remove the inspection cover. 25mm down to the top of the fuel.

Weeping from the starter sections is best cured with the blanking plate kit weber will supply. Or the full cold-start elimination kit

http://www.webcon.co.uk/shopdisplayprod ... rchfields=

They take the preverbial on price but it does work

[elanner]

Simon,

Ah, that's interesting, thanks.

I must be the only person who actually likes the starter circuit. The sheer simplicity (crudeness?) of the design appeals to me and I use it whenever cold starting. I find it very effective and don't have to bother futzing around with the accelerator pump.

That said, it's an area of the Weber that can go wrong and most people never use it, so I can understand why it gets blanked off. Perhaps I should do it temporarily to prove my leaking theory....

Nick

[simonknee]

To be fair I think I remember Keith warning that the 25mm level could result in fuel "splashing over" on inclines and perhaps in hard cornering. Maybe this is why Weber went with a conservative value but it is at the expense of driveablility. Though Keith basically thought that Weber (or at least the guy that wrote the manuals at Weber) didn't have a clue what they were doing. Every time I see reference to that old document on this site's technical section I shudder at how bad my Elan drove before I followed the ways of Keith. It should come with a health warning.

Another example of bad Weber documentation is that they do not document how to correctly use the air-bleed-bypass adjustments you get in later 40DCOE. They are very effective at ensuring the airflow is matched through all barrels and preventing stumble when moving off idle. Yet you would not know this if you read the official Weber set up.

Keith also suffered from fuel leaking around the starter cover plates even with carbs set to his exacting tolerances. I did too but since I disconnected the choke cable back in 2003 it was a no brainer to blank it all off.

[oldchieft]

Simon,

Ah, that's interesting, thanks.

I must be the only person who actually likes the starter circuit. The sheer simplicity (crudeness?) of the design appeals to me and I use it whenever cold starting. I find it very effective and don't have to bother futzing around with the accelerator pump.

That said, it's an area of the Weber that can go wrong and most people never use it, so I can understand why it gets blanked off. Perhaps I should do it temporarily to prove my leaking theory....

Nick

+1 for the cold start device.

It is a lot less crude then the two dabs of the throttle.

It saves jetting neat petrol past an open inlet valve and washing the oil off the bores and diluting the lube oil.

Also after the engine is running you have to have the idle mixture set rich to stop a stumble on pickup.

The guys who built these knew what they were doing.

Jon the Chief

[1963Turnerjohn]

Wanted to know - is this the plate that the breather hole should be added to ??

Hi and Happy New Year,
I had a similar problem that eventually started leaving a puddle of fuel under the engine. It used to manifest itself a few minutes after shutting down the engine after having driven the car.
The following is what was suggested to me. I followed this procedure which cured the leak.
Regards,
Colin.


Throttle lever housing cover plate dribbles:

? The throttle lever housing cover plate is between the two barrels and is fixed with two countersunk screws. (Figure 1 ? item 80)
a) Remove the screws and plate. A full sealing gasket should be in place. Remove it and check if the chamber is wet with fuel or shows signs of this.
b) Fuel can enter the chamber via the pump rod hole or the return spring hole. Yes I realise this should not be the case BUT do you have ANY clearance in the butterfly shaft bearing on either side of the chamber. Of course you do even if it?s only small.
c) When you are pulling 5000 to 6000 + rpm and lift off the throttle you can appreciate many inches of vacuum generated must suck from anywhere it can. Herein lies our problem. Fuel is sloshing around in our float bowl through corners and clearances around pump rod and throttle return spring hole are considerable. The vacuum pulls fuel into the chamber but there it just builds up to gradually dribble over our distributor or hot exhaust as the case may be.

Solution to throttle lever housing cover plate dribbles -

Drill a 1.5 mm ?breather hole? in the cover plate and match drill the gasket. The hole should be level with the top screw and half way to the edge to miss the housing cast edges.
The small hole stops the effect of the vacuum but also keeps the dirt out of the throttle lever chamber. Screw the plate back on for dry, dribble free motoring.

This really is an incredibly simple fix for a rather obscure problem. It took a lot of reasoning and close inspection to analyse what was actually happening but investigation is part of the problem solving. It was only after I fixed the problem that a carburetor repair person suggested that this was probably why Weber modified some plates in the 80?s with a 8 ? 10 mm hole in the middle. Unfortunately Messers Weber don?t tell everyone why they did this modification.

NOTE: Obviously all of these fuel checks are better if carried out shortly after a run so wet fuel can be seen when the carburetors are removed.

Ok, calling all Weber experts. I've looked through my Weber tuning books and the archives here but cannot find anything conclusive for the problem I have. Recently purchased and rebuilt a pair of 40DCOE27. OE fitment on Alfa's. The carbs look great and I used Webcon service kits. Installed and running great, however after running the front carb starts dripping fuel at the mounting to the head, past the O rings. I've removed the carb twice and checked/replaced everything I can think of and all looks good. I can leave the car sitting with the carbs full and no leaks. Idling and cracking the throttle and no leaks. It seems to only occur after I've been for a drive and after shut off and a few minutes standing it starts to leak - not dripping but quite wet.
So, anyone with any good ideas?

[bitsobrits]

No!!

The location is given in the text you copied into your post: the rectangular plate between the throttle plates on the head facing end of the carbs. The plate can't easily be seen with the carb attached to the cylinder head.

[SENC]

[alan.barker]

FDB6923F-6891-493C-80E2-9067452E57DE.jpeg (94.08 KiB) Viewed 582 times

There you go.
Alan