WEBER 40 DCOE types

PostPost by: RichC » Sat Jan 21, 2012 9:44 pm

hi folks,
I've trawled thru the archives to try and uncover the difference between the different type numbers . How does pair of 18s differ from 31s, 35s 151s etc
my '68 +2 is running on what I think are the original type 31s , if anyone can confirm that? I picked up that the type 18s were quite common on 60's elans.
Would a pair of 34s 35s or 151s be any good with the right jets etc swapped in?
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PostPost by: Jeff@Jae » Tue Jan 24, 2012 5:00 pm

Given the choice the 151s are the best. They have steel throttle shafts that don't twist over time and handy air bleed adjusters that allow accurate synchronization throat to throat in each carb. They will do the job with the jetting swap. With the original 18s on my S2 I find that to get exact synchronization I have to carefully un twist the bronze throttle shafts due to the center pull throttle linkage. About once every two years of heavy right foot fun.
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PostPost by: elans3 » Tue Jan 31, 2012 7:50 pm

I agree, if you're not bound by the originality bug, then 151's are better.
However, on no account buy 34's or 35's, they were made for a specific Rootes Group 1725cc engine and are quite different, and don't work well on most other engines, particularly Twincams.

That's why you see so many advertised on Ebay and the like on x-flow and Pinto manifolds, they've bought them, tried them and they can't get 'em to work correctly.
They can be modified to work ok, but it ain't worth it.

There's also a huge myth building up around Spanish made 151's which quite frankly is a load of bull.

Yes they did have a problem with porosity on a batch made during their first attempts in the early 80's, and yes the castings aren't quite so crisp, but given the choice between an old pair of knackered 18's or 31's, and a spanking pair of Spanish 151's I'd go for the latter anytime.

I work with DCOE's every day, and nowadays you have to accept that they have their limitations, but in period they were a superb piece of kit.

Hope that helps,
Steve
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PostPost by: gjz30075 » Wed Feb 01, 2012 12:52 pm

But to answer RichC's question, the difference amongst them is the number and placement of the progression holes, and 'off the shelf' settings and jetting. The differences are shown in the various weber books.

I, too, have the 151s (thanks Jeff@JAE) and couldn't be happier. Yes, rougher castings, loose screws and overtightened screws when I first got them, but once sorted, they really work well.

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PostPost by: elangtv2000 » Wed Feb 01, 2012 3:28 pm

+1 on 151s - the progression circuit and other features give them better throttle response and tuneability. They look like copies compared to original Italian production, but as long as they are machined properly, work great. They are also widely available and not that pricey.

Cheers,

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PostPost by: bob_rich » Fri Feb 03, 2012 5:51 pm

Hi Rich

Firstly I must say that I am not anything like an expert on Weber carbs but I though I would put into one place the variuos bits of data I have on them. I am sure someone more skilled in the art of weber tuning than me can comment (confirm) but I think the 151 are of Spanish extraction and I think they were use on the Lotus (and Caterham) Seven S3 Sprint and Super Sprint using the Ford crossflow engine.

My only other useful experience is that over the years I suspect many Carbs may have been "Tuned" by "Experts"! In its earlier years my seven was a normal GT with the single twin barrel progressive carb. During an earlier rebuild when I striped it down I found that variuos jets and tubes had been changed from the original spec. I rebuilt with the recommended parts and it was a lot better after that.

hope that helps best of luck

Bob
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PostPost by: elans3 » Fri Feb 03, 2012 7:32 pm

Hi Bob, sorry but 151's were made in Bologna first, a few years before production went to Spain. I have 2 sets of Bologna made 151's in my garage now.
Similarly, 45DCOE 152's were made in Bologna before the production transferred.

As we've said before, the Bologna made ones have slightly "crisper" castings,
Kind Regards
Steve
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PostPost by: RichC » Sun Feb 05, 2012 6:52 am

Thanks chaps. That's very handy to know. Think I'll look out for a pair of 151s now ...
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PostPost by: RichC » Sun Feb 05, 2012 7:22 am

there's a pair of 72/73s on ebay ???? are they possible candidates ?
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PostPost by: elans3 » Sun Feb 05, 2012 9:28 am

DCOE 72 / 73's were original equipment on the 70's and early 80's 1.8 Alfetta.
If they haven't been changed, they will be choked and jetted with :-
Chokes 32mm
Mains 135
A/C 210
Idle 55F17
Pumps 35
Em. Tube F34


All except the pumps will need changing. Very expensive for a pair. at new prices something over ?100 . I'd carry on looking for a good pair of 151's, their standard setting from the factory come very close to std Elan settings.

Steve
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PostPost by: RichC » Fri Feb 24, 2012 10:56 am

Thanks Steve for a good set of 151s!

I can't tell you what a difference to tuning it has made & I haven't done anymore than warm it up at mo...

The old webers(31s) had all serviceable items replaced when I got the +2 back on the road a couple of years ago, but it was never easy to balance carbs & get fuel mix right & tune them despite having all the right tools for the job.

Straight away within a minute of fiddling with the mixture screws I got the sweetpoint on all 4 and the airflow in all 4 the same .
Fabulous !
Can't wait to take it for a spin at the weekend once I've sorted the little niggle of the throttle bar .
I need to be able to secure the end of it somehow to stop it from coming out of place & jamming the throttle open see pic below ...
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PostPost by: elans3 » Fri Feb 24, 2012 12:16 pm

Richard, very glad you're pleased, it's amazing the difference they make in comparison to a worn pair .

I would just dress the casting lug back enough to clear under all conditions and potential positions of the throttle arm. Alternative is just to bend the arm away slightly,

Kind Regards
Steve
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Elan S3 FHC Pre-Airflow 1966
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PostPost by: RichC » Fri Feb 24, 2012 5:49 pm

sorted the throttle bar . Found a Ba thread nut to screw on the end and have alraldited in place .

Next Issue ... Trumpet length . The ones on the old carbs were i presume the originals and were very long . The ones on the 151s are very much shorter ...(see pic)
Am I right in thinking the engine will run leaner at high rpm as a result ?
Any other comments on impact of much shorted trumpets ?
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PostPost by: elans3 » Fri Feb 24, 2012 7:19 pm

Richard, that's not always the case. What you have to remember is that the optimum distance from the end of the trumpet and a filter backplate is around 35mm, certainly no less. If your original trumpets were closer than that, then I'd use the ones I provided with the carbs, (which are the shortest you can get and are normally used with a fairly shallow KN), or source some that will give you that 35mm clearance.
Only real way is to get it on a good rolling road, which I would recommend
Steve
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Elan S3 DHC S/E 1966
Elan S3 FHC Pre-Airflow 1966
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PostPost by: holywood3645 » Sat Feb 25, 2012 3:46 am

I have a set of the 151 that I have just installed on my LHD S4. My question is with throttle linkage. i would like them to operate from with the cable entering from the top, (like the strombergs) however the parts that I can source seem to lead me towards the cable entering underneath tha carbs for operation.
Any advice?
James
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