Lotus Elan

Twincam expert help

PostPost by: chrisbeck » Tue Sep 28, 2021 10:16 am

I think it's time to seek expert help, I've got a low throttle misfire and have run out of ideas. Replaced everything on the ignition side and have eliminated a high speed RFI issue, now think it must be carburation.
Can anyone recommend someone who knows their way around a Twincam with Dellorto's local to me in South Bucks, UK, who can do a diagnosis?
Thanks.
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1973 Lotus Europa Special (under restoration)
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PostPost by: cliveyboy » Tue Sep 28, 2021 12:02 pm

I have Heard good things about these people. Based near Winchester
https://www.aireytuning.com/
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PostPost by: chrisbeck » Tue Sep 28, 2021 12:16 pm

Thanks, I spoke briefly to a guy at Kop Hillclimb on Sunday and he recommended a garage in Maidenhead (I think) who'd worked wonders on his Elan. He said he visits this forum frequently so maybe he'll spot this and remind me of their name!
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PostPost by: lotusfan » Tue Sep 28, 2021 12:36 pm

chrisbeck wrote: he recommended a garage in Maidenhead (I think) who'd worked wonders on his Elan.


Maybe Steve Williams Sportscars?

http://swlotus.com
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PostPost by: JohnP » Tue Sep 28, 2021 12:37 pm

Max Hurst. Max 500 in Guildford.
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PostPost by: cliveyboy » Wed Sep 29, 2021 7:14 am

Chris
That might have been me.
I used a local classic car specialist in Oxfordshire.
https://classic-car-services-oxford.co.uk/
Toni sorted out my Sprint running badly when I was struggling. (Newish Lumenition faulty which caused some other electrical issues).
He does not have a rolling road but worth a call.
Clive
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PostPost by: nmauduit » Wed Sep 29, 2021 8:12 am

chrisbeck wrote:I think it's time to seek expert help, I've got a low throttle misfire and have run out of ideas. Replaced everything on the ignition side and have eliminated a high speed RFI issue, now think it must be carburation.
Can anyone recommend someone who knows their way around a Twincam with Dellorto's local to me in South Bucks, UK, who can do a diagnosis?
Thanks.


if you are unsure about the carburetion somehow (I understand you've cleared out possible ignition issues, and would have made sure carbs are clean and nominally jetted - but also and more importantly if everything else is stock the fuel level in the bowls), a measure of richness may be a quick way to assess that more accurately than by the look of spark color via the use of a wideband lambda sensor. The best is to have a bung welded to the exhaust, but one can also get a measure at the exhaust, though less accurate (esp. a low revs)
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PostPost by: 69S4 » Wed Sep 29, 2021 9:07 am

cliveyboy wrote:Chris
That might have been me.
I used a local classic car specialist in Oxfordshire.
https://classic-car-services-oxford.co.uk/
Toni sorted out my Sprint running badly when I was struggling. (Newish Lumenition faulty which caused some other electrical issues).
He does not have a rolling road but worth a call.
Clive


Hi Clive

Great to chat to you at Kop Hill on Sunday. I went there expecting to spend most of my time amongst the two wheelers but the Lotus owners were much more interesting! :lol:

Despite being just up the road from me I hadn't come across Classic Car Services before. That's another one to add to my list of small local specialists to turn to when things go pear shaped.

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PostPost by: LaikaTheDog » Thu Oct 07, 2021 7:08 pm

Novatech in Slough
Novatech.info
he worked on my Weber's and removed a Low rev stumble, I have seen him tuning a 2 seater Elan also.

Knows what he is doing.
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PostPost by: chrisbeck » Sun Oct 10, 2021 3:10 pm

nmauduit wrote:
chrisbeck wrote:I think it's time to seek expert help, I've got a low throttle misfire and have run out of ideas. Replaced everything on the ignition side and have eliminated a high speed RFI issue, now think it must be carburation.
Can anyone recommend someone who knows their way around a Twincam with Dellorto's local to me in South Bucks, UK, who can do a diagnosis?
Thanks.


if you are unsure about the carburetion somehow (I understand you've cleared out possible ignition issues, and would have made sure carbs are clean and nominally jetted - but also and more importantly if everything else is stock the fuel level in the bowls), a measure of richness may be a quick way to assess that more accurately than by the look of spark color via the use of a wideband lambda sensor. The best is to have a bung welded to the exhaust, but one can also get a measure at the exhaust, though less accurate (esp. a low revs)


I wonder if I've disturbed some debris when I removed the carbs, either that or should have fitted new O-Rings on the manifold plates and I'm sucking in air? How difficult is it to check the jets are clear? Can I do it with the carbs in situ?
1970 Lotus Elan S4 SE
1973 Lotus Europa Special (under restoration)
1990 Morgan +8
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PostPost by: ericbushby » Sun Oct 10, 2021 3:31 pm

Hi Chris,
An easy test for air leaks inwards at the carburettor plates is to spray a little carb cleaner or similar volatile fuel there. Propane will probably work equally well.
If there is a leak then the engine will respond to it.
Eric in Burnley
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PostPost by: chrisbeck » Sun Oct 10, 2021 3:45 pm

Good idea, thanks!
I'm reminded of listening to a colleague's +2 and being able to hear the carb sucking air because he'd trapped an O-Ring, it was too high a frequency for him to hear. Next time I saw him he had hearing aids!
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1973 Lotus Europa Special (under restoration)
1990 Morgan +8
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