Weber advice

[Esprit2]

To follow on from Tim's analogy..
If she is built for comfort the top end performance won't be there
If she is built for speed she will be fussy and dificult to live with on tickover

Boy, is that ever food for a different thread...

Are the 151's the right carbs for an elan?

The 40DCOE-151 is the modern, Spanish-built version. It does have some internal differences compared to the early versions Lotus used, and will no doubt require some re-tuning after the engine is running in order to achieve the same end result.

Also, I've heard some less than complimentary things about the quality of the Spanish Webers.

Early Lotus applications used 40DCOE-18, and later ones used 40DCOE-31. Still later ones yet switched to Dellortos, and never went back.

For the most direct plug-n-play on a stock engine, I'd shop for a set of 40DCOE-31 and start with the Lotus set-up. Internal differences in the -151 versions, the progression holes in particular, will probably mean some creative tuning will be required to get the engine running well. I'm sure they can be made to work well, but they'll require some effort.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[AHM]

Tim,

Nice explanation earlier.

Re. the 151?s the progression holes were what I was alluding to but did not have the knowledge or experience to comment ? Allan I would do some reading about making 151?s work on an elan.

Simon

[promotor]

That's a really simplified version how venturi carbs work, but hopefully it gives you a mental image of what's going on. Constant Depression carbs, like SU and Zenith-Stromberg, are a different kettle of fish, and require a different understanding.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

Well written and interesting. I wonder if you could do a write-up (in another thread) about the workings and science of the SU/Stromberg?

[gearbox]

Tim, Thank you for the wonderful write up. I actually visualized what was going on with the carb as I was reading the post. "I see said the blind man". Needless to say, I will be reading it again several more times with an exploded diagram and my disassembled carb in front of me. Thank you again. BTW I did email Matthew the day you mentioned him, no response yet.

I'm a bit confused about your comments about the 151 carb. I recieved the carb from a dyed in the wool Lotus enthusiast (owns 10 of these things, some of which he was the original owner). The carb came from a original Sprint which he was restoring. He opted for a new 151 carb and I believe he took the choke and emulsion tubes, losing the emulsion tubes in the transfer. That's how I got the carbs with the 30mm choke without the emulsion tube assemblies. But he was pretty adamant that they were original. The carbs I have are marked DCOE 151 and "Made in Italy", so perhaps they were very early production before being made in Spain and somehow they got into Lotus production? If so, that means these things should have been made around 1973/4. Maybe better than the Spanish ones?......... I hope.


Simon, Thank you for the links, I will follow up on them. But my initial search on this forum turned up some very positive information and reviews on the 151. Apparently the 151 was a replacement for the 31 and while the early Spanish versions had casting defects, but after it was corrected, it was said to be better for low idle adjustment as it had a steel throttle shaft. I haven't found anything on the progression holes yet, but will keep on searching. Seems like I have no alternative but to become a Weber expert by the time I get this car running lol. As for suitability of the 151's for an Elan, I'm beign told that they were OEM on late Sprints, but who knows. Jeff from JAE swears by them for the Elan, but then again he sells them lol. But thank you for the help and let me know if you find that progression hole thread.

[Esprit2]

The carbs I have are marked DCOE 151 and "Made in Italy", so perhaps they were very early production before being made in Spain and somehow they got into Lotus production? If so, that means these things should have been made around 1973/4. Maybe better than the Spanish ones?......... I hope.

Allan,
The Sprint Twin Cam used 40DCOE-31 carbs, and, to the best of my knowledge, the 40DCOE-151 was not original to any Twin Cam or Elan. I don't have hard documentation on the -151's introduction date, but I'm quite certain they came out well after Elan production had ceased.

The dash numbers were pretty much sequential, with each new revision or upgrade getting the next higher number... there's a big gap between -31 (Sprint spec) and -151 (current production). I have heard that -151's were available in the 1980's, I can't confirm that. That would be closer to Elan production, but still after it had ended.

The current box-stock 40DCOE carries the -151 suffix. (The current 45DCOE is the -152.)

I don't know what to tell you about where your carbs came from, but I'm inclined to doubt they ever saw the inside of the Lotus factory.

Early -151's were built in Italy, so that part is possible. And yes, I'd expect the Italian ones to be better. At the very least, the castings are more crisp. As I understand it, DCOEs are not built in Italy any longer, and production has moved to Spain and Germany.

Regards,
Tim Engel

[fatboyoz]

Allan,
You could go to this site and ask Keith your original question:

http://autos.groups.yahoo.com/group/sid ... l/messages

You may have to join the forum to post.

Regards,
Colin.

Tim, Thank you for the wonderful write up. I actually visualized what was going on with the carb as I was reading the post. "I see said the blind man". Needless to say, I will be reading it again several more times with an exploded diagram and my disassembled carb in front of me. Thank you again. BTW I did email Matthew the day you mentioned him, no response yet.

I'm a bit confused about your comments about the 151 carb. I recieved the carb from a dyed in the wool Lotus enthusiast (owns 10 of these things, some of which he was the original owner). The carb came from a original Sprint which he was restoring. He opted for a new 151 carb and I believe he took the choke and emulsion tubes, losing the emulsion tubes in the transfer. That's how I got the carbs with the 30mm choke without the emulsion tube assemblies. But he was pretty adamant that they were original. The carbs I have are marked DCOE 151 and "Made in Italy", so perhaps they were very early production before being made in Spain and somehow they got into Lotus production? If so, that means these things should have been made around 1973/4. Maybe better than the Spanish ones?......... I hope.


Simon, Thank you for the links, I will follow up on them. But my initial search on this forum turned up some very positive information and reviews on the 151. Apparently the 151 was a replacement for the 31 and while the early Spanish versions had casting defects, but after it was corrected, it was said to be better for low idle adjustment as it had a steel throttle shaft. I haven't found anything on the progression holes yet, but will keep on searching. Seems like I have no alternative but to become a Weber expert by the time I get this car running lol. As for suitability of the 151's for an Elan, I'm beign told that they were OEM on late Sprints, but who knows. Jeff from JAE swears by them for the Elan, but then again he sells them lol. But thank you for the help and let me know if you find that progression hole thread.

[Esprit2]

Apparently the 151 was a replacement for the 31 and while the early Spanish versions had casting defects, but after it was corrected, it was said to be better for low idle adjustment as it had a steel throttle shaft. I haven't found anything on the progression holes yet, but will keep on searching. Seems like I have no alternative but to become a Weber expert by the time I get this car running lol. As for suitability of the 151's for an Elan, I'm beign told that they were OEM on late Sprints, but who knows. Jeff from JAE swears by them for the Elan, but then again he sells them lol. But thank you for the help and let me know if you find that progression hole thread.

I can think of no reason why the -151 shouldn't work well on the Elan's Twin Cam. The only concern is that internal differences between the -151 and -18 or -31 will require minor jetting changes to compensate. The Lotus manual gives Standard Twin Cam jetting for the -18 and -31... I'd start with the -31 set-up. But don't get your expectations too high... there will most likely be some follow-up tuning required to get the -151 running best. When they're good, I'm sure they'll be great. Just don't expect it to happen in one shot using the book set-up.

The big benefit of the -151 design is the addition of Air Bleed Screws and Vacuum Ports for connecting a 4-tube manometer. This is a great tuning/ balancing aid that Dellorto DHLA carbs had, but early Webers didn't have. IMHO, the Carbtune II is the best 4-tube manometer on the market, and with one of them hooked up, balancing is quick and easy.

Early -151s had three progression holes, and later ones got 4 (Lotus Dellortos had 6). I doubt that you'll find published data on hole size or location. That's no big deal, since the progression holes aren't something you should mess with anyway. Not unless you really know what you're doing.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[Esprit2]

Allan,
You could go to this site and ask Keith your original question:
http://autos.groups.yahoo.com/group/sid ... l/messages

You may have to join the forum to post.

Keith at Sidedraft Central eats, sleeps and breathes Weber carbs. He even makes custom parts for them and knows the Twin Cam application. The only downside is you may get overwhelmed with a flood of info.

Yes, you will have to subscribe to the group in order to participate.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[Esprit2]

Just some -151 settings for comparison. Probably not worth much to your cause, so don't let it confuse you.

?.......................... Caterham 7 .... Part Number
Application .............. SuperSprint ... 19550.174
............................. Crossflow ....... Type 151
Tuning Priority ......... 1700 ............. BOX STOCK
Manufacturer .......... Weber ........... Weber
Model & Size ........... 40DCOE 151 ... 40DCOE 151
Choke .................... 32 ................ 30
Main Jet ................. 120 .............. 115
Main Air Correctors ... 165 .............. 200
Emulson Tubes ......... F16 .............. F11
Auxiliary Venturis ...... 4.5 ............... 4.5
Idle Jets ................. 45 ................ 45
Idle Air Correctors ..... F9 ................ F9
Accel. Pump Jets ...... 35 ................ 40
Needle Valve ............ 1.75 ............. 1.75
Float Height, mm (in) . 12 (0.472) ..... 12 (0.472)
Float Material ........... Plastic ........... Plastic

Note that vintage DCOEs had brass floats, and more modern examples have plastic floats. The height settings are different for the two types:

Brass:... 8.5mm (0.335") Height
........... 15 mm (0.591") Drop

Plastic: 12.0-12.5mm (0.472-0.492") Height
........... 25 mm (0.984") Drop

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[gearbox]

Early -151's were built in Italy, so that part is possible. And yes, I'd expect the Italian ones to be better. At the very least, the castings are more crisp. As I understand it, DCOEs are not built in Italy any longer, and production has moved to Spain and Germany.

Regards,
Tim Engel

Maybe China? http://www.alibaba.com/product-gs/36430 ... retor.html

Mathew finally got back to me, his suggestions are as follows"

I would suggest:

32 chokes
135 mains
175 airs
45F9 idles
40 pumps
F11 emulsion tubes

This should be about right.

Now this is different from the factory set up. I'll reach out for Keith and sees what he suggests, but I think it's becoming a bit confusing again.

[Elan45]

Allan,

There is a page in the Webers section of the Elan factory manual about detuning the Sprint carb settings, because of driveability issues. Knowing where you live and will be using the Elan, I'd certainly start w/ 30mm and if this Elan turns into more of a track day car, then move up to larger chokes for more top end performance. You are savvy enough that you'll pick it up quickly once you have it running.

Roger

PS: Very good explanation Tim of how Webers, really all fixed choke carbs work.
Oh, and Allan, you're in for a treat with the Webers. That growl they create really puts a smile on my face and I have 30mm chokes and std comp ratio, B cams and SE header. Plenty of go on the street. RLS

[Esprit2]

Maybe China?
http://www.alibaba.com/product-gs/36430 ... retor.html

There's more than one Chinese knock-off of Weber carbs out there. OER is another. Solex and Mikuni also make DCOE clones, but they're done with formal licensing agreements... they're "official" in one way or another.

Mathew finally got back to me, his suggestions are as follows" (Snip)...
Now this is different from the factory set up. I'll reach out for Keith and sees what he suggests, but I think it's becoming a bit confusing again.

Allan,
I think it's confusing because you seem to be seeking one answer. There isn't just one, and the correctness of any solution depends upon your goals. If a variety of answers confuses you, then I think you should stop asking. Build the engine as you have decided to do... with Lotus' 30-choke set-up. Once it's running, address any specific stumbles or hesitations as they occur.

The settings Matthew gave appear to be for a high performance application (it's pretty rich), and the 32 chokes indicate he was presuming a high rpm power peak. Not what you've been talking about on this forum. Most customers who go to the effort of converting to Webers are in pursuit of more power. If not given some specific guidance, Matt would probably presume, "More power, More Power, MORE POWER!!" And it appears he did.

Did you just say, "I'm installing 40DCOE-151s on a Lotus Twin Cam, what choke & jetting set-up do you recommend?" Or did you add, "I'm more interested in street driveability, and will be using Lotus' "Standard" set-up for the smaller, 30mm choke 40DCOE-31 as a starting point (not S/E or Sprint). Given the internal differences between the -31 and -151 versions of the DCOE, are there jetting differences I should make going in?"

Given Matt's answer, I'm guessing he was working with the (perhaps mistaken) understanding that you were seeking more power. The answer you get depends upon how you ask the question. Keith, not knowing you any better than Matt did, will be faced with the same dilemma of understanding your goals. Don't make him guess.

Keith has also put a lot of time into developing special replacement jets he calls Hypo-jets. They're supposed to be the ultimate answer to Weber driveability problems. His ultimate answer will probably involve converting your carbs to Hypo-jets. If that just confuses you more, then tell him up front that you just want to get the engine running in near "Standard" trim (not S/E or Sprint) before launching into any mods. One step at a time.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)

[elans3]

Hi All, just to say that 40 DCOE 151's work very well on Twincams. I work with DCOE's on a daily basis, and indeed have sold sets to a few members on here who have been delighted with the results obtained over the old 18's and 31's. I've also sold at least another 6 or 7 sets to go on T/C's to people that are not on this Forum.

Most of these people, have fitted them to standard spec engines, and have just swapped over all the chokes and jets into the 151's with good results.

One thing I would say, is that if you are contemplating using the SE spec 32mm chokes and 150 air correctors, you will probably find the car has electric acceleration at full throttle, but it will be a pig to drive around town. That's certainly been my experience, having owned three standard S3's, and all three exhibited this trait. In each case I swapped to the Factory advice written as an addendum in the Factory manual, ie 30mm chokes and 200 air correctors.

151's were originally made for quite a long time in Bologna, I have 3 in stock at the moment.
I've been doing this for nearly 4 years now, and hundreds of carbs have passed through my hands, I guess the ratio of Italian 151's to Spanish has been about 1:3
Don't be put off by the Spanish versions. It's true that they had a short period when they first started , where a batch of castings were showing porosity, but they rectified that quite quickly.
Yes the castings still aren't as crisp as the Bologna ones were, but give me a Spanish 151 with no wear rather than a knackered old 18 or 31 that's been "refurbed" many times in the last 40-50 years any time.
The 151 also has the benefit of having the extra airscrews which means you can adjust the air mixture to a finer degree, and also you can attach a manometer to a tapped hole in the body, for even better balancing

Another plus is the fact that the 151 utilises a composite rubber top gasket, and this keeps the damp out much better than the old paper one. Virtually 100% of 151's I open when I get them are pristine inside, which I can't say about the older Bologna carbs.

Much of the bad publicity about Spanish 151's is BS, based on a few early problems, and visually poorer castings, but nowadays, they're a great replacement for the carbs on our engines.

Hope this helps,

Steve
elans3

[gearbox]

Thanks Tim, sounds like a plan, I'll stay with the 30mm configuration. I was hoping for a plug and play answer, but I guess that was a bit nieve and optimistic. I contacted Matt very early durning this post, so while I did mention driveability, I just gave the same info I posted, level of engine rebuild, and what would a good safe starting point would be. As for keith's site, yeah, a bit above the curve for me right now, maybe at stage 3 or 4 of my progression of dialing in the carb, but for right now, I'm ordering parts for the stock 30mm set up.

Steve, thanks for clearing up the 151 shadow, I guess these Italian ones I have were a very early replacement back in the day on the car it came from. But I was concerned about having another variable of the progression tubes to deal with, I'll approach that when I get to it. Also thanks for reinforcing the 30mm choice, I'm definietly more interested in idle and low to mid end performance where the car will be 75% of the time. If I need more, I'll address it when the car is idling and running without stumbling. Thanks again Allan