Weber Installation - Thackeray Washers

[AHM]

I was just trying to point out that it's important to check both gaps, spacer and coil.

That'll be why we agree - My post was a follow on from Bill's, trying to point out that it wasn't simply about the 'O' ring.

[twincamman]

I use 2 anti vibration washers or split washers instead of tackery washers . Combined with anti vibration nuts it's a one tighten and forget it deal . Also easier to find than the Thackeray that went into hiding at 1 in the morning ....ed

[reb53]

As to why they're there, this explains it.

free-parking-f45/origin-the-thackeries-t24310.html

Ralph.

[abstamaria]

Rereading the good comments here when reinstalling the Webers on my spare engine (gap not critical in this case as it is unlikely the motor will be used in the near future).

Andy

[elanner]

Just a quick question - on replacing the carburetor flexible mount O rings should they be smeared with something to improve the seal?

-----------

Spring has vaguely arrived in Boston so I got the Elan started again last week after almost 4 months of silence. All seems well with just a couple of new work items appearing. One of them emerged after a good 70 mile run yesterday - petrol leaks from the Weber flexible mounts.

Rohan's fire has made me (and hopefully all of us) much more vigilant about dampness under the carbs. As far as I can tell both rear carb mounts are leaking - with general wetness over the fuel pump and chassis both behind and in front of the pump. Initially I suspected the pump itself until I fortuitously spotted a few drips falling from above it. #3 seems to drip onto the pump, while #4 drips onto the chassis behind the pump.

For carburation experts, I'm curious as to what leak behaviour would be expected. If some level of vacuum is the most common situation in the inlet manifold how would drips occur? The 5-6 drips that I saw were after the engine had been switched off, which is also a bit perplexing. I never saw any drips while the engine was running, but the general wetness makes me think that they must be happening.

Even more surprising is that the engine is running very nicely - smooth idle, no roughness or coughing or anything. I have no reason to suspect air leaks but presumably it's not possible to have a fuel leak with no air leak.

Nick

[billwill]

Those O rings should not leak even if un-greased, so if the leak is at the O ring, I would guess you either have pitted surfaces or simply the thackray washers & nuts are not done up tight enough or you need O rings.

Have you got the one-piece intermediate plates or the aluminium intermediate seperartor with 2 o-rings in each. If the latter the grooves may have muck in them.

But you need to check for leaks ar the top carb gasket and the idle jet adjusters as well.

[Galwaylotus]

Just a quick question - on replacing the carburetor flexible mount O rings should they be smeared with something to improve the seal?

Probably belt-and-braces but I did put a light smear of Permatex Super Lube grease on the O-rings. It was as much to protect the rubber as it was to ensure a seal.

[fatboyoz]

Nick,
Something to consider.
Cheers,
Colin.

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.



europatek wrote:
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?

Just a quick question - on replacing the carburetor flexible mount O rings should they be smeared with something to improve the seal?

-----------

Spring has vaguely arrived in Boston so I got the Elan started again last week after almost 4 months of silence. All seems well with just a couple of new work items appearing. One of them emerged after a good 70 mile run yesterday - petrol leaks from the Weber flexible mounts.

Rohan's fire has made me (and hopefully all of us) much more vigilant about dampness under the carbs. As far as I can tell both rear carb mounts are leaking - with general wetness over the fuel pump and chassis both behind and in front of the pump. Initially I suspected the pump itself until I fortuitously spotted a few drips falling from above it. #3 seems to drip onto the pump, while #4 drips onto the chassis behind the pump.

For carburation experts, I'm curious as to what leak behaviour would be expected. If some level of vacuum is the most common situation in the inlet manifold how would drips occur? The 5-6 drips that I saw were after the engine had been switched off, which is also a bit perplexing. I never saw any drips while the engine was running, but the general wetness makes me think that they must be happening.

Even more surprising is that the engine is running very nicely - smooth idle, no roughness or coughing or anything. I have no reason to suspect air leaks but presumably it's not possible to have a fuel leak with no air leak.

Nick

[billwill]

Or you could fit Dellortos instead of Webers as the Dellortos don't have that hidden chamber.

[Galwaylotus]

Heresy!!!

[Esprit2]

+1 on what Colin, fatboyoz, wrote about adding a vent hole to the cover plate. That is a real leak potential that can be easily avoided.

Also, the fit of the chokes and the auxiliary venturis must be tight when assembled and/or can get loose. The assembly depends upon having airhorns with the proper length sleeve that pilots into the throat. If those bits are loose, fuel can leak into the throats, and from there find a way out.

Actually, switching to Dellortos is not heresy. There's precedence in that Lotus switched from Webers to Dellortos on later production Twin Cam engines (1972 onward ?). Dellortos were Lotus own approach to solving the number of Weber related problems. I have twin Dellorto DHLAs on three engines, and a single DCOE on a Europa S2's Renault engine. That one Weber causes me more maintenance and tweeking work than all my Dellortos combined cause. IMHO, Dellortos are an improvement in running and reliability with no apparent downside, other than a new learning curve.

Dellorto was an engineer at Weber, knew the issues, and figured he could design a better carburetor by starting over. And he did.

Regards,
Tim Engel

[Galwaylotus]

It was meant as a joke, hence the " "!

[Esprit2]

Yup, and I saw the humor.

But like a lot of humor, it strikes very close to the truth... which is why people recognize it. While you're one-word comment is funny, it also points in a good direction.

Regards, and no offense intended,
Tim Engel

[Galwaylotus]

None taken.

[elanner]

Wow - you guys are great. Multiple answers in 24 hours.

The idea of the leaking cover seems to address the symptoms better than my leaking O ring theory (it's impossible, of course, to actually watch a leak drop off the underside of the carb, so I was guessing).

The O ring center plate is crushed up against the manifold for #4, so no doubt it makes sense to change them all once I've got the carbs off, regardless of anything else.

The thing about the drips I saw was that the engine must have been off for a few minutes by then. I had been poking at the fuel pump for a while before I saw one. Also, on restarting the engine and turning it off again I couldn't induce any more drips. And lastly (I didn't dare write this in my original note!) I really got the impression that a few drips were going slightly sideways, implying that they were spat out. Of course, it's all over in a flash and not repeatable, so I couldn't swear to it.

Anyway, the vent hole seems like a sound idea.

All of a sudden my Easter weekend is busy. Along with the Boston Marathon on Easter Monday (just watching, of course, and bomb free, we all hope).

Nick