Lets just hope that the 45's are the italian made and not the spanish ones. I have heard a few bad reports about them now in reguards to poor casting quality, made from USA's famous 'Cheese' aluminium.

has a 35mm crack in the float bowl over where the venturi sits, problem found.

I know there is probly a set of 45s on now. But I will throw in my bit cos I would like to know what is wrong. Have you heard of a leak detection machine that injects smoke under pressure into small areas. ie exhausts intakes. I use one of these at work & they work extremly well. If you can get the use of one remove the float bowl cover & fill the ventury up & you will see a small trace of smoke coming up from any small cracks. Did you try a differant fuel supply to elimanate any fuel tank issues?

just red full post
good luck with new carbs
i couldnt give up, i would need to no problem
my guess is the casting is pooruss/tinny little holes
was once blocked, carby soked and cleaned now leaks
had this prob before

OK, good home right here!

All of these things we have tried unfortunatly, the only thing left that could possibly do this is a crack in the actual body. Being 27's they have obviously seen abuse in some way or other during their life, I think I am just having #OOPS#ty luck with them.

They are coming off today.

My 40's leaked yeas ago, and I tracked it down to two issues.
1st being that in the early days of my cars development I had no fuel return line. Carbs in general specifically Webers dont take too well to the needle and seat being kept under constant pressure, and 2nd, the gasket and alloy cover on the base of the main body[located on the underside of the fuel bowl] was not sealing 100%, it was weeping more that dripping.

From memory the cover plate covers the underside of the "inlet valve with exhaust orifice jet, which works in conjunction with the pump jet to regulate the duration of fuel delivered during acceleration.


Another plausible explaination of your carbs is that the idle cct is leaking down via the progression ports and then weeping down under the auxillary venturies and then down past your soft mounts.

edit: the more I think about it there are so many possibilities with DCOE weber losing fuel. If the pump jets are not seated correctly, [there is usually a little ally washer which sits between the brass jet and the alloy carb body] then the fuel could make its way out.

best of luck with it.

I dont even need to leave them overnight,

I primed them 2 hours ago (left fuel pump on for 20 seconds without starting, shut it off and watched the pressure drop to zero instantly) checked float level with the main jet assy removed spot on 29mm, put a few sheets of FLpa (paper that changes color when it gets wet with hydrocarbon's)under the carbs, within 5 minutes it started dripping and the float level dropped 15mm in 2 hours. Definate crack in the body... drips out the front carb's second trumpet, crack must be around the venturi

Ohh well, this motor could do with some 45's with 36mm chokes anyways because im reving it up at 8500 to 8800rpm. Looking forward to the upgrade

By the way, ive almost always ran my carbs at 18-20kpa (2.7-2.9psi) tried 1, 2 and 4psi previously with the last set without any difference

Rezlo - I'm very sorry to hear of the trials you've been put through. Without knowing more, it's indeed possible there's a crack in them, or a casting imperfection, and when 'warm' the leak is not visible because the fuel can evaporate at the same rate it's seeping out a small hole.

For what it's worth, sometimes there is good sense in the peace of mind of starting fresh with a known new and flawless carb.

In very very general terms - I'm not going to make out I'm the world expert on carbs, but I've done a fair bloody chunk of time on a bunch of different carbs - webers as a general rule should _not_ go out of tune. Almost always (and this goes for SU type carbs too) if they are going out of tune, it's actually traced back to stuffed throttle shafts, which never re-set to the same exact amt of air flow when they go back to the idle position, as they are leaking air through hte shaft, and/or it's a case of weak/flimsy linkages which likewise don't produce consistent/equal opening from carb to carb.

If there is one achilles heel of webers, it's already been mentioned - they are EXTREMELY sensitive to fuel pressure, and anything above around 3-3.5psi fuel pressure and they will over run the needle and seat, and produce inconsistent and overfuelling because they are overfilling/flooding the fuel bowls and then the engine. EVen many std factory mechanical fuel pumps have an output too high in pressure to be appropriate for a weber. If it's only leaking overnight, maybe just maybe there is a blocked breather and the tank is ballooning from petrol vapourisation over time, but that's a long shot imho.

For all you know the reason these sets of 40dcoes came up for sale was there was a previous issue with them, and somebody has sold them on and kept quiet about the known problem, leaving you to do a sherlock holmes and try and find out why.

What else comes to mind - actually here's an odd tid-bit. I've mentioned here and there that I've been into early (i.e. the original ones) minis, and also the locally produced hemi 6 cylinder chargers. An odd thing I can mention is that both of these have been weber shod (the hemi 6 pack chargers had triple webers from the factory, and any historic mini racer runs a single weber on a long neck inlet, or possibly twin split webers). Now here is the funny thing. The hemi guys, as a rule tend to run a specific 'solid' style gasket between the weber and the manifold, and swear by them, as the rubber ones allow too much vibration (this is partly because they are on a big tall 6 cylinder, with a moderately long intake manifold, so they are spaced out fairly far so 1-2 degrees engine movement = a greater distance of travel up that high and out that far to the side. Now on the other hand, on minis, these solid gaskets see the carbs with short distance but high frequency vibrations, and the needle and seat can't keep closed, and they overfill and are all over the place as far as consistency goes. Nearly everyone in contrast on a mini runs the rubber o-ring imbedded gaskets between weber and manifold and is sure not to overtighten the nuts holding the weber to the manifold - and on the mini that combo tends to dampen out the vibrations and keep it 'on song'. I am aware of an exception or two here or there, but that's almost universally the different case for each engine. it's a long shot, but maybe give the opposite to whatever you are running a try and see if it worked.

Having said all that, I'm sure everyone here (myself included) wishes you a 100% trouble free upgrade, and the end of all hassles, with the fitment of the 45dcoes!!

About the only other thing I can think of with the old 40s is to maybe add some type of really strong/thin dye to a load of petrol, and run the fuel pump to fill the fuel bowls, and then leave overnight and see what happens - maybe the source/location of the seepage would become apparent??

Good luck mate!

My problem is that these carbs are done by the best Weber guru in the country, he charges a LOT and honestly they look beautiful and when the car runs they fine, its bloody leaking, it has to be a crack in the body and after 2 years of messing around with them im done... Refund leaves me only $300au short of brand new 45's, I have more than $300 in fire damage, let alone one motor rebuild due to bore wash.. $300 to go from used leaking POS's to brand new 45's seems like a good idea to me