Weber Carburetors

[TomMull]

My Plus 2 S Elan is undergoing a chassis transplant, so perhaps a good time for a carburetor tune up. On close examination I find that there are 2 different Weber 45 DCOE on it. As far as I can tell, the car had two Strombergs originally and the Webers were added by the PO some time in the distant past.

As seen in the photos, the top covers are slightly different as are the numbers. (40DCOE 18 vs 40DCOE 151).

Question then Does it matter?

 

[Tybalt]

Does it matter? I do not have a definitive answer on that, here is what I can tell about the two different carburetors that are on the car. The 40 DCOE 18 is an Italian made Weber AFAIK and would have been either a non North American market fitment or semi-shady (emission controls related) dealer installed option of part of a conversion done by a previous owner or shop of previous owners choice. The 40 DCOE 151 is a Spanish made Weber and happens to be the only 40DCOE currently in production from Weber. It looks like most of the jets and main venturi are interchangeable, but the auxiliary venturi and the the floats are not. The float setting is done differently between the two but needle and seat are the same basic part number, but like the , venturi, jets and emulsion tubes, you will have to make sure that whatever is fitted matches from carburetor to carburetor.

Here is an early 40DCOE manual and parts list that would cover the 40 DCOE 18 as well as 40 DCOE 151 parts list to review for part differences between the two. My personal opinion is that you should run a matched set so all of you set ups match. Unless you are going for a concours winner either unit paired together looks like it would work. If you are thinking concours winner, you need 2 of the 40DCOE18.

https://www.carbparts.eu/books/dcoe_service_manual.pdf

http://racetep.com/media/pdf/40DCOE151.pdf

Classic Motorsports has had two sets of 40 DCOE 18 carburetors restored in the last few years one set at Pierce Manifolds, the other at Weber Carburetor Restoration. If nothing else you might try contacting Frank Filicicchia of Famous Franks Lotus Parts. Carburetors are really outside of what he does but it wouldn't surprise me to find out that he knows of someone he could recommend.

 

[TomMull]

Nice to get such a knowledgeable and detailed response and thanks for the links attached. Logic would indicate that a matched pair would be in order and you've confirmed that. Rebuilding the two miss-matched ones does not make sense although trying them as is might be an option.
The car will be a driver hopefully, far from concourse. The Webers were installed by a previous owner as far as I can tell and the car had Strombergs originally, which hints at another cheaper option although with dozens of cars in my past this is the first with Webers so that might be hard to do.

Perhaps somebody's got an orphan 40 DCOE 18?

Tom

 

[NutmegCT]

Wondering out loud here ... how did/does the engine run with the two Weber carbs that are on it?

 

[Tybalt]

If they were jetted and "venturied" to match and correctly for the engine and altitude, with those parts being the same/interchangable and the floats set to the two different requirements of the two different carburetors, it should run decently enough. Both units are DCOEs, just different specific models of the DCOE, the theory of operation for both are essentially the same, but still a matched pair would be better in my mind.

Something my grandfather taught me was that for an engine to run you needed three things and three things only, compression, a reasonable fuel air ratio mix and spark at the right time. If you have those three things, the engine cannot help but start and run. And if you think about it, a single DCOE is really two single barrel carburetors that happen to share a common float bowl. The strength of the DCOE, IDA, IDF, etc is that they are almost infinitly tunable, that also happens to be their downfall. If you don't put some thought into it and just start changing out parts you can find yourself way off in the weeds and struggle to get back so keep good notes when changing things.

 

[TomMull]

Nutmeg,
I can't answer that. Here's why in case you're interested, but not really very interesting.
I bought the car sight unseen a few years ago from California and had it shipped to my home here in NH. The pictures looked great, the car appeared in to be complete and in good condition. The paid third party condition report was positive except that it mentioned that the engine had not been run. The seller also told me that. The engine did turn over and had compression, so how bad could it be?
The rusty chassis and sills were a surprise though and that's why I put it in the corner for a few years. I've now replaced the sills and I found a new chassis at a reasonable (for Lotus) price. I've booked that job for this winter.
I got into the carbs since they need to come off for the chassis removal.
Oh and I'm into the dash wiring harness, another challenge as is does not match much of the Factory Manual's diagram.
Strangely enough, I do all this because I like it. Few regrets.
Happy motoring,
Tom

 

[DrEntropy]

If the engine had Strombergs originally, what head is on it now??

The Weber head is much different than the Stromberg one.

As for the differences in the Italian vs. "Spanish" versions, the 40DCOE18 is what was fitted on pre-emission units, AFAIK.

Not near the "pile" of spares just now,but may have an errant 40DCOE18 in there. Will check within the next 48hours and report back.

 

[TomMull]

I can't answer which head either but I can say it was a 1970 Federal model which should have been post emissions, I think. Build record shows Feb 1970 Federal Specifications. So the option to revert to Strombergs would not not easy.
If you do have a 40DCOE18 I'd be interested, thanks.

 

[DrEntropy]

That is decidedly a Weber head, Tom. Likely changed at some point. After '68 the US cars were with Stromberg heads, the ports were "Siamesed" to accommodate two single carb throats. The head castings were different. There have been some "conversion" setups to allow fitting twin Webers but we've never run across one.

No chance yet to dig thru the parts but possibly t'morrow.

 

[NutmegCT]

"I bought the car sight unseen a few years ago from California and had it shipped to my home ..."

That's become quite the activity for folks over the years, especially when "browsing the 'net" for a car to fix up. I always recommend people see the car in person first, or hire *someone from a nearby car club* to check it out personally.

Anyway - we're here to help.

Tom M.

 

[TomMull]

Tom M, Not the first time I've done this!
T

 

[DrEntropy]

A pair of 40 DCOE 27's (Alfa 1600, IIRC), a lone 40 DCOE 4 (Alfa for sure) but no orphan DCOE 18's.

Esthetically, the "151" would get head-shakes from the concourse crowd, but so would a Weber head on a 1970 chassis Elan+2. I'd say jet the later carb to match the original and press on. The white plastic caps cover air by-pass circuits, I would think closing those and re-jetting would be one solution. Idle jets in particular.

 

[TomMull]

Thanks anyway. The car will never submit to a concourse judge, at least not under my stewardship, but the mismatched carbs are a bit of a glaring fault. PM sent.
Tom

 

[PAUL161]

There is a Weber idf on Tulsa Craigslist for $40.00. Know little about Webers, just posting for someone if interested. PJ

 

[Tybalt]

I thought I would hold up until the good Dr. had a chance to chime back in on possibly having a DCOE18 sitting around. We now have that answer so here is my take on things if I ran the zoo or asylum, take your pick.

I would want a matched set of carbs, if you can find a more period correct DCOE18 and then have it and your existing DCOE18 rebuilt by a Weber Specialist such as Mike Pierce at Weber Carburetor Restoration, that is probably the best answer:

Weber Carburetor Restoration | Salinas California

Webercarburetor Restoration is equipped for nearly every stage of restoration on Weber carburetors. Weber carburetors restored and tested on one of the original Weber carburetor test bench from the Weber factory in Bologna, Italy. We have restored over 7000 Weber carburetors to "Runs like new...

www.webercarburetorrestoration.com

And even though carburetors are outside his normal part of the Lotus spares and restoration parts business, I can't help but think that it would not hurt to check in with "Famous Frank" to see if he has any thoughts on Weber rebuild and restoration service providers.

The other option would be to double check you existing 40DCOE151 to make sure it is a Spanish* built unit with the plastic floats and either have it rebuilt and mate with a new 40DCOE151 or just buy a pair of brand new Weber 40DCOE151s (not some of those knock offs that are floating around out there on the interwebs) and have them set up for your car. Above I had stated "the theory of operation for both are essentially the same" with essentially being the key word. The 151 was sort of developed to be a more emission friendly unit and the differences in operational theory are primarily tied to the way the progression circuits are set up and that is one of the tie ins that DrEntropy is alluding to when he mentions the white plastic caps and the air by pass screws. I have heard that some people that have altered the progression holes in the 40DCOE151 to make them more like the 40DCOE18 or 40DCOE2, but personally do not know anyone that has done so. I know that I don't have the type of equipment to want to try such a thing.

Here's another rabbit hole to head down. Figure 11 shows an idle enrichment hole and figure 12 shows the idle enrichment screws, note what they say about different screws having differing tapers. Figure 22 shows the progression holes in the bore of the carburetor while figure 23 shows the progression holes from the access port on the top side:

Weber DCOE Carburetor Reference: Theory, Configuration,Tuning & Reference Documents

* Rumor central has it that there were supposedly some very early on Bologna built 40DCOE151 carburetors, but every 40DCOE151 I have ever seen was Spanish built.

 

[DrEntropy]

* Rumor central has it that there were supposedly some very early on Bologna built 40DCOE151 carburetors, but every 40DCOE151 I have ever seen was Spanish built.

I would be curious as to which float is in the 151 Tom has. The cover is stamped "Made in Italy" so it may be one of the rumored Bologna units.

I do have a pal who has rebuilt Webers for a long time, many for the concourse Amelia-type crowds. Problem is, he's back-logged and not taking in any more work. The Pierce guys are a best bet if you farm it out, IMHO.

 

[Tybalt]

I would be curious as to which float is in the 151 Tom has. The cover is stamped "Made in Italy" so it may be one of the rumored Bologna units.

....

Good catch, I missed that. New glasses with "progressive lens" and roll off when transitioning from one focal length zone to another coupled with the astigmatism correction has been eating me up as I try to get used to these things. Dammit, I thought these things were to help me see stuff!

The float question is a good one, it is my understanding that the metal floats can be fitted to a 151 but you still have to set things to the 151 specifications. Never tried it so no first hand data here.

 

[TomMull]

I would be curious as to which float is in the 151 Tom has. The cover is stamped "Made in Italy" so it may be one of the rumored Bologna units.

I don't know how definitive the plastic float is but here it is:

 

[Tybalt]

Plastic, the metal ones are brass and with the float part being more cylindrical in form.