Lotus Elan

Weber 151 jet needed for the 1600 lotus twin cam (elan 1968)

PostPost by: elans3 » Fri Nov 20, 2020 1:01 pm

Good to hear. let us know how you get on when you fit them !
Current :- Elan S3 DHC SE S/S 1968,
1963 Alfa Giulia Ti Super Rep.
Previous :-
Elan S3 DHC SE SS 1968,
Elan S3 DHC S/E 1966
Elan S3 FHC Pre-Airflow 1966
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PostPost by: mini90 » Thu Nov 26, 2020 2:53 pm

good afternoon

I'm on the step of checking the twin weber DCOE 151 config for my car before starting engine

Image

my car is a +2 S130/4 1972on

could you tell me if this config could run correctly or what I have to change before:

Chokes 50
Main Jets 120
Air Corrector jets 155
Emulsion Tubes F11
Idle jets 50 F8
Accelerator Pump Jets 35
and something unidentified writed 750 85F9

This is my first car with weber carbs and I don't know exactly how it work...
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PostPost by: elans3 » Thu Nov 26, 2020 4:39 pm

If your +2S130 still has it's "Big Valve" engine, the spec for jets for your carbs should be as follows :-
Chokes 33 (You must have misread the choke size, 50mm chokes is not possible.)
Main Jets 120
Air Correctors 155
Emulsion Tubes F11
Idle jets 50 F8
Accelerator Pump Jets 35
The "something unidentified" are the starter jets. Don't worry about them, as they only come into play when the cold start mechanism is connected, which you should never need to do once the carbs are set up correctly.(they aren't the right ones for a big valve engine, but you don't need them anyway).

I note that your carbs are the much later 40 DCOE 151's ie. not original for a Sprint or +2 130 Big Valve engine.
Originally they would have been either Weber 40 DCOE 31's, or Dellorto 40 DHLA's.
No matter, the jetting spec above will work fine. Once up & running, you just may find that the 151's need a slightly richer idle jet, as they are a later "emissions" type carb. In my experience, some do, some don't.
The great thing about 40 DCOE 151's, are A). They have the auxiliary airscrews for balancing the airflow between two barrels of one carb. and
B). They have sealed ball bearing throttle shafts, seals on the idle airscrews to prevent air leaks, and rubber top cover gaskets to better prevent damp getting into the float chambers when being stored.
Hope that helps
Current :- Elan S3 DHC SE S/S 1968,
1963 Alfa Giulia Ti Super Rep.
Previous :-
Elan S3 DHC SE SS 1968,
Elan S3 DHC S/E 1966
Elan S3 FHC Pre-Airflow 1966
elans3
Third Gear
Third Gear
 
Posts: 257
Joined: 12 Sep 2003
Location: Doncaster, South Yorks.

PostPost by: mini90 » Thu Nov 26, 2020 8:27 pm

Many thanks for this helpful answer
I will check the choke size, maybe i have misread as you said

Tomorrow i will try to start the engine and balance carbs with motorcycle 4 ports synchronizer
It's always a pleasure to find in this place all these technical informations
mini90
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Posts: 49
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Location: france

PostPost by: elans3 » Thu Nov 26, 2020 8:44 pm

You're very welcome.
Just a thought. When you said they were 50mm chokes, were you looking at the chokes, or the auxiliary venturi's ? There's just a chance that you may have 5.0 aux venturi's in them, which, for the Lotus Twincam, should be 4.5.
The auxiliary venturi's are what you can see in the carb barrel when looking at a fully assembled carb, and are held in place by a slightly pointed grub screw which, on a 151, screws in on the underside of each barrel.
The chokes are located behind this venturi, and are held in place by the auxiliary airscrew (to stop it rotating in the barrel, and are located underneath the white plastic caps, one on each barrel, topside), and a brass pin , set into the side of each choke, see exploded view below link :-
https://www.webcon.co.uk/weber/40dcoe.htm
Current :- Elan S3 DHC SE S/S 1968,
1963 Alfa Giulia Ti Super Rep.
Previous :-
Elan S3 DHC SE SS 1968,
Elan S3 DHC S/E 1966
Elan S3 FHC Pre-Airflow 1966
elans3
Third Gear
Third Gear
 
Posts: 257
Joined: 12 Sep 2003
Location: Doncaster, South Yorks.

PostPost by: elans3 » Thu Nov 26, 2020 8:47 pm

You're very welcome.
Just a thought. When you said they were 50mm chokes, were you looking at the chokes, or the auxiliary venturi's ? There's just a chance that you may have 5.0 aux venturi's in them, which, for the Lotus Twincam, should be 4.5.
The auxiliary venturi's are what you can see in the carb barrel when looking at a fully assembled carb, and are held in place by a slightly pointed grub screw & locknut which, on a 151, screws in on the underside of each barrel.
The chokes are located behind this venturi, and are held in place by the auxiliary airscrew (to stop it rotating in the barrel, and are located underneath the white plastic caps, (again, with a locknut, one on each barrel, topside), and a brass pin , set into the side of each choke, see exploded view below link :-
https://www.webcon.co.uk/weber/40dcoe.htm
Current :- Elan S3 DHC SE S/S 1968,
1963 Alfa Giulia Ti Super Rep.
Previous :-
Elan S3 DHC SE SS 1968,
Elan S3 DHC S/E 1966
Elan S3 FHC Pre-Airflow 1966
elans3
Third Gear
Third Gear
 
Posts: 257
Joined: 12 Sep 2003
Location: Doncaster, South Yorks.
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