Weber 40 DCOE Types - what's yours?

[TANGO7]

There appear to have been a number of different Weber 40 DCOE types fitted to Sevens over the years, with perhaps the most common being the 151. I am trying to ascertain if there is an "standardisation" or "development" in relation to this and what actual types were fitted. 

What have people got fitted or has anyone replaced worn out carbs with a particular type.

I am particularly interested in the types fitted to the various Crossflow engines

[Roger King]

I'm not an expert on the different suffixes but quite often they indicate a version made for a specific purpose. Having been out of the business for over 15 years I may be out of date, but so far as I know the 151 is still the current "general purpose" version that is expected to be re-jetted to suit whatever purpose the customer has.

The really big difference appeared in about 1980 (only an approximation). Before this DCOEs had plain throttle spindle bearings that wore out rapidly, circular brass floats that often sprang a leak, and no idle bypass screws for the butterflies. Later ones are vastly better, having ball races for the spindle bearing, black plastic rigid foam floats that can't puncture and idle bypass screws. I suspect they were forced into this by the fact that Dellortos had all of those features.

The idle bypass screws are the easiest way to spot later carburettors; they are positioned, one per barrel, on the outside of the body near to the butterflies. When new they had white plastic caps on them, covering the adjuster screw and locknut.

Unless you are after historical accuracy, I can see no sensible reason to use the earlier type.

[cobaltcodd]

88 xflow - type 151

[NigelHeard]

Hi, i have a couple sets of 40 DCOE's one set on a  spare Lotus Twin Cam which has a big vale conversion on a head that was reworked by Bill Quine while he was at Downton these are 31's the others are fitted to a Competition Engine Services tuned 711m crossflow engine from my project S4 which I think are the same type 31's but they are at my mates garage at the moment hope this is some help but these older cars may have gone through many upgrades.

Nige H.

[john g]

95 xflow - type 151 

[7 wonders of the world]

ISTR from my days on the rollers that the early versions had a small bleed hole in the butterfly to compensate for the 1st progression drilling being in the wrong place too.

[HendrixsWhiteStratReturns]

1990 Xflow 1700 SS - 151s

 

[Golf Juliet Tango]

Already I know more about DCOE 40s than I have done after 22 years of driving behind a pair.

[blueyedbiker]

Quite.  How does one tell which version they are?  Mine's on 45's.

[TANGO7]

The Type is stamped on cover plate, following "Tipo" (which in my wisdom I deduce is Italian for Type). It will take the form of DCOE40  (or 45 I guess) followed by some more figures. (e.g. 34 or 35 as in my case).

This was the reason for my initial interest as this Type, fitted to my '92 Factory CKD 1600 Crossflow, seems to vary from the "usual"151 (if anything can be regarded as "usual" in Caterham production). I wondered if Caterham had got hold of a batch of carbs which were not their ususal spec and fitted these to a batch of Sevens at one time. (No Factory Records exist, nor would I expect them to,  to detail this, as checked with Martin Phipps), My Carbs perform fine, presumably being fitted with the requisite jets for Caterham application, as noted above would be done to the 151s

   

[HendrixsWhiteStratReturns]

[AnkerB-S]

Mine are 151s. 87 1700 SuperSprint.

But I did have an interesting issue with the carburetors: The car had a flat spot between 2000 and 3000 RPM and it spat through the carburetors on partial throttle. Also, big explosions out the exhaust.

I asked around whether all SuperSprints had this issue and got more nos than yeses. I made an appointment with a shop that is familiar with Webers and they diagnosed the idle jets as being too lean. They ordered the next size up and what difference! No flat spot, no spitting, and no explosions!