Weber 18

[Dieschelan]

Hi

I have in my S3 Weber 18 carbs. Are there different to Weber 31. Can I tune the engine with these carbs? Should I put the early type airbox?

Regards

[nmauduit]

you can tune 18 the same way one tunes 31 (changing jets chokes etc), the remaining difference being progression holes (harder to modify, try at your own risks, I would not in most cases).

As for the airbox, if you have a later airbox and like it, you actually may get a bit more power from that as the early type tends to restrict flow to #4 cylinder...

[Dieschelan]

Thank you for the reply. Can I put sprint cams without problem?

Cheers

Diego

[nmauduit]

you sure can. The tuning of the issue 18 may be a bit more finicky to smooth out the idle to main transition (different progression holes), but I would try that first if the carbs came with the car and are in good condition.

[elans3]

The accelerator pump stroke in 31's is also greater than in 18's. Although you'd never notice it in day to day running.
Differences in progression holes similar to above. Don't try to modify those. You can use either 2's, 18's, or 31's successfully on a Twincam, although the latter two are slightly better (newer design).
Alternatively, especially if your originals are worn, use much more modern 151's. They last longer, don't suffer as badly from internal oxidisation, don't suffer from worn throttle spindles / bushes, and seal better. They also have the auxiliary airscrews, which help in fine tuning much more. They don't look quite as nice, but are a way better bet than an old pair of worn out 18's or 31's.

[TBG]

Diego - 18s re fine but it can sometimes take a fair bit of time and trial and error to get the jetting right. Believe me I have just been there!! D

[miked]

+ 1 for the 151's
I bought some nice Italian ones from elan3 about 8 years ago for a plus 2.
Way better.

[Andy8421]

Collecting parts for my impending restoration.

My carbs are 40DCOE18, and look to be original (filthy, corroded and knackered). Having trawled the forum, the consensus seems to be not to bother with trying to restore, but to replace with modern 40DCOE151s.

Is this still the accepted best route?

If so, there is a gentleman on eBay selling 151s at a good price. Has anyone any experience of the seller?

https://www.ebay.co.uk/itm/201022020967?epid=23027212161&hash=item2ecdd89d67:g:9zoAAMXQlgtSrflK

Thanks in advance for any comments.

Andy.

[2cams70]

To all those tossing out original Italian Weber carbs - please toss them my way. I’ll gladly take them off your hands!!!

Remember that Weber are just a niche supplier of old antiquated technology to hobbyists these days. Back in the day they were supplying product to virtually all the major motor manufactures. These manufacturers for the most part didn’t accept junk. There just isn’t the same incentive to produce quality product as existed back then. The car manufacturers in fact used to send engines to Weber in Italy so the carbs could be properly calibrated. They didn’t try and calibrate them themselves.

[Craven]

My experience of well used 18’s is as the many many reports, fuel leaks, one sort or another.
Lots of theories put forward on remedies, most involve extensive reconditioning with no guarantee they will function as new.
Unless you are after originality, new carbs will have all the evolved ‘improvements’ that to a large degree overcome failings of earlier types, non-precise adjustment of emissions at idle for one.
FWIW

[nmauduit]

If so, there is a gentleman on eBay selling 151s at a good price. Has anyone any experience of the seller?

I've purchased repro jets from him some years ago and they actually fitted (which is not always the case), also other smaller new parts for webers, remember him as reliable for what I got (standard disclaimer apply, no affliliation on my mpart)

PS: I've not seen often Weber 151 made in Italy ... but quite often ads mentionning Italy for carbs with "made in Spain" on the top cover...

[2cams70]

Generally the only things that will kill the original Webers are butchery by ill informed repairers, impact damage and severe corrosion. Wear isn’t an issue because all the wearing parts are available and replaceable. Later improvements such as sealed bearings and steel throttle shafts can be retrofitted.

The 151’s are more of a “universal fit” Weber suited to a wide variety of engines. They are cost down in areas like the throttle disc retaining screw which is a large cheese headed screw rather than the nicely countersunk low profile earlier screw that was used. The originals were calibrated specifically by Weber for the engines they were intended to be used with and given a specific Tipo number accordingly.

If you have significantly modified your engine the 151’s properly calibrated may be better but if you engine is relatively standard there is no reason to change.

[mbell]

I am in the 151 camp but also think 2cams70 has very valid points here.

I don't think there is a right answer here and as every it depends on skill of the person and the state of the carbs. In my case I did a basic rebuild of the carbs that came on my car but couldn't get a good balance on them. I looked at the cost of new bearings, spindles and plates etc which added up to quite a bit and seemed better to buy new than throw money at carbs of unknown condition. This also gives me the advantage of air bleed screws and vacuum ports.

If I had more experience with rebuilding them then maybe I would have gone that route. But I didn't have confidence that they would be fixed and suspected I might end up spending even more money try to sort them out. Or have to buy new ones later wasting money.