Lotus Elan

Dellorto DHLA set ups

PostPost by: Midlife » Sun May 13, 2007 7:45 pm

I have a standard 130S/5, this the first real time of running the car since I got her. I have run the engine once before a while back, and it was quiet i.e. problem free. It was running really rich though! Anyway I have now finished my overall project and I also rebuilt the carbs with a maintenance kit but kept all the original jets in.

I have now started the car again with the re-built carbs on and it is running very rich with poor revving, puffs of black stuff etc. all the signs. Having done some research, I realise that all is not how the book says (Des Hammill). This is what I have in the car and I realise it is rougly what is in the "tech tips section" on this forum?

- Chokes 33mm
- Main Jet 120
- Main Jet Emulsion Tube 7772.5
- Main Jet Air Correction 130
- Idle Jet 50
- Idle Jet Holder 7850.2
- Pump jets 45

But if you research on what should be in there you come up with...

- Chokes the same 33mm
- Main Jet 135
- Main Jet Emulsion Tube 7772.10 or 8
- Main Jet Air Correction 160+
- Idle Jet 45
- Idle Jet Holder 7850.8
- Pump jets 35

Does anyone agree with the new set up? Has anyone got a set up they could advise?

Cheers

Doug
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PostPost by: bill308 » Mon May 14, 2007 3:27 am

Doug,

I'm not a Dellorto expert but I did do a fair amount of research on the subject when I bought a set of refurbished DHLA 40E carbs back in 2005. I have yet to fit them.

I looked at specs from the Baby Elan Work Shop Manual, Wilkins, Robinshaw & Ross, and Dave Bean. The settings covered important details like what model carb your have (early no suffix, E, G, or other?), what cams are are fitted, standard or big valve?. State of tune should also be considered.

Your current setup is consistent with Wilkins specs for an early DHLA 40 (no suffix) carb fitted to a Domestic Big Valve engine with a D-type (Sprint) cam, except that Wilkins calls for a 35 pump jet rather than your 45. I logged a question mark on this one item though. Dave Bean shows the same settings for a DHLA 40 on a Sprint, +2, and 130S, but differs in that he calls out a 45 pump jet. Wilkins lists a float level setting 14.5-15 mm. Did you check your float level and freedom of movement? Sometimes they drop and get hung up. There should be a droop limit.

The other thing is that jets, air correctors, and other internal pieces are sometimes drilled out without leaving a record or note to the new owner, so be warned. I would also double check your cam timming based upon a true and confirmed TDC. What's your fuel pressure?

The internals you cite should be close to what's needed based upon my research. I hope this helps.

Bill
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PostPost by: Craig Elliott » Mon May 14, 2007 5:31 pm

Doug

Are you using a fuel additive?

I think my +2 S130/5 has the same carbs as yours and the same carb set up. I believe the rest of the engine is more or less to standard sprint spec. I have had problems with it apparently running rich (sooty plugs, missing etc) but the main cause of this seemed to be the type of fuel additive I was using. Changing from using Castrol Valvemaster + (i.e. with an octane boost) to using Valvemaster (i.e. without) made a big difference. This plus ensuring that the carbs are balanced and the mixture properly seemed to be the key to getting the engine in mine running properly.

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PostPost by: Midlife » Mon May 14, 2007 8:35 pm

Thanks for the feedback... I did test the float level and check on re-build, interesting point is though after thinking things through I thought of coming down a size on the pump jet as well or rather do this as the only change first, and see what happens. WRT to the fuel additive, I have put octane booster in, I didn?t realise it would make a difference in that way? I do have the sooty plugs though!! which brings me to the next point? before I go changing things I think it might be worth giving the car a good fast/hard run and check the plugs after high rpm, i.e. check its running correctly up the top end.

Thought I would put a pic of the car in as well, she has gone from road going to track, and I was busy during the winter! Just got the rear suspension to do now.

Cheers

Doug
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PostPost by: Craig Elliott » Tue May 15, 2007 9:38 am

Doug

Looks very good... may be worth topping up the fuel in the car using no lead replacement additive. The valve seats in twincams are apparently pretty hard so I tend to only put in additives when I'm on a long motorway journey. I couldn't (and still don't) understand why the use of the octane booster made the car run rough but it definitely did - I'd clean the plugs off and it would run fine for a few miles then they would soot up and the car would miss, not rev etc. This could have been down to the particular brand I was using - having solved the problem I haven't bothered to investigate further. Using the non-octane boost additive made a vast difference.

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