Lotus Elan

DHLA 40 E Specifications

PostPost by: bill308 » Wed Aug 17, 2005 6:10 pm

I'm getting ready to acquire a set of Dellorto DHLA 40 E carbs to replace a pair of ageing Weber 40 DCOE 18's on my 1966 S2 SE Elan. The engine is fitted with Sprint cams, Sprint intake valves, and the ports have been matched to the O-ring carriers, the exhaust headers and the large intake valves. Compression ratio is slightly increased from a stock 9.5:1 to about 9.8:1, verses the Sprint's 10.3:1.

Some early Elans were fitted with DHLA 40's for which jetting is well defined. Some late model +2's and Sprints were fitted with the later DHLA 40 E's which are in effect very early emission carbs in that they are capable of extended operation on the progression circuit which has 5-progression holes verses the 40's 3-holes. The E-model also has provision for barrel-to-barrel balancing with air bypass circuits, a different float assembly, and I believe some minor differences in the idle circuit.

Other than a tech bulletin that references a different float setting because of a different float assembly, I have not been able to determine any differences in jetting from the early DHLA 40's. Does anyone know if indeed there are other differneces?

Thanks,
Bill
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PostPost by: marcfuller » Wed Aug 17, 2005 10:10 pm

Hi Bill,

Robinshaw & Ross (p79) shows the following differences between the Big Valve Domestic and Big Valve European Emmisions Dellortos

Market -- UK Domestic -- European Emissions
Model -- DHLA40 -- DHLAE40
Choke -- 33mm -- 32mm
Main Jet -- 120 -- 135
Main Air Corrector -- 130 -- 200
Idling jet -- 50.02 -- 47L
Pump Jet -- 45 -- 33
Float Assembly -- 7298-01 -- 7298-02

Other things like the emulsion tubes are the same spec for both DHLA40 and the DHLAE40

Hope it helps.

Regards, -Marc
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PostPost by: bill308 » Thu Aug 18, 2005 2:59 am

Thanks Marc,

I don't have the text you cite but seeing your post prompted me to consult my copy of the "Lotus Twin Cam" Revised Edition 2nd reprint autumn 1996, by Miles Wilkins. Sure enough, he had specifications for Dellortos as follows:

.............................Domestic S/E....European......Domestic.........European
.............................small valve.......small valve....Big Valve.........Big Valve
.............................C-type cam......C-type cam....D-type cam.....D-type cam
carb type...............DHLA 40..........DHLA 40E......DHLA 40..........DHLA 40E
choke.........................30...................30................33.................32
main jet......................115.................120..............120...............120
air corrector jet...........160.................200..............130...............160
slow running jet...........50...................45L..............50.................50L
idle-jet holder.............7850-2............7850-4........7850-2...........7850-1
emulsion tube.............7772-1............7772-5........7772-5...........7772-5
pump jet.....................40...................33................35.................33
starter jet...................70....................70..............70.................70
starter emuls tube......7482-1.............7482-1.........7482-1..........7482-1
needle valve...............150..................150..............150..............150
air-horn length(mm)....40....................40...............40................40
float levels(mm)..........14.5-15*..........16.5-17........14.5-15.........16.5-17
idle speed (rpm)..........900-950 ..........900-950.......900-950........900-950

*If there is persistent flooding, set the float levels to the European specification.

Type DHLA 40 is used on all domestic small valve and Big Valve engines.
Type DHLA 40E is used on all European ECE 15 engines.

Domestic in column headings denotes UK domestic.
C-type cam is as used on Elan S/E models.
D-type cam is as used on Elan Sprint models.

I hope the above table comes out readable. It's a real pain in the butt to present comparison information like this any other way.

Bill
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PostPost by: marcfuller » Thu Aug 18, 2005 3:30 am

Appreciate the follow-up. It is always interesting to see the differences in specs, even between respected texts. Guess that's what tuning to engine and locale is all about.

BTW - With the difference, I rechecked my numbers, they are accurate as to the text I quoted.
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