Lotus Elan

Dellorto DHLA40s

PostPost by: Orsom Weels » Fri Dec 22, 2017 7:24 pm

vincereynard wrote:I've heard about twisting the spindle to balance both barrels in an individual carbs but cannot see me trying it.


No, DON'T do it !
That's a bad piece of misinformation given in the Lotus WSM. The correct way to balance the barrels of an individual carb (that doesn't have the air bleed screws) is to drill a small hole in the throttle plate of the side that is down on suction. Start with a very small drill, you can always enlarge it if it isn't enough, & if you go too much, solder it up & start again :) . If you twist the spindle, you will have one barrel on progression ahead of the other, not the way to make an engine run smoothly :shock:

Regards, Tim
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PostPost by: vincereynard » Fri Dec 22, 2017 8:01 pm

I had no intention of trying Tim - as I said " cannot see me trying it".
Drilling a tiny extra hole would be a good idea. Would it make any difference if it was top or bottom? Although a somewhat laborious procedure. It might help mounting the carbs. on hinges!

alan.barker wrote:That's just it with 4 columns you can see if there are balance problems between the chokes in the same carb :wink:
Alan

What I mean was swap the tubes going to the Carbtune - see if there is a difference in readings. So if you had 1 > 1 , 2 > 2 etc and, say, 4 showed a difference to 3. Swap the 3 & 4 tubes and it should show the same.
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PostPost by: john.p.clegg » Fri Dec 22, 2017 8:12 pm

"drill a small hole in the throttle plate of the side that is down on suction"

surely you mean "up on suction"?

With a bright light down the venturi you can see the progression holes being uncovered and if need be " set " the butterflies accordingly

I was that man

John :wink: .
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PostPost by: Orsom Weels » Fri Dec 22, 2017 8:49 pm

Afraid I've only got a synchrometer John, you need to allow a little more suction on the barrel that reads low, hence drilling that plate. It would be opposite if the vac take offs are engine side of the throttle plates, none of my carbs have them. Sorry for any confusion :oops:
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PostPost by: Fredtech » Sat Dec 23, 2017 11:19 am

Guys.

Weber are possibly ahead of the game here. Take a look at a set of 40DCOE31?s, as fitted to S4 and Early Sprints.

These have various changes to the Jets and Choke Size, but they also have a 1mm hole drilled in the butterfly.

I was told, some time ago, by a knowledgeable Lotus fan, that Lotus could not get the original?s to idle right, hence the additional hole in the butterfly.
(Weber must have done this mod, as these carbs are fitted to some Alphas as well)

May be myth, may be nonsense, but it makes 31?s easy to spot at a rummage-sale, as they are the only ones with holes in the butterfly?s, despite what the number on the Top/Lid might say.
Attachments
40dcoe-31-pic-2.jpg and
John "Freddie" Nelson, Berks UK
26/3212 - Rebuilding
S4-Sprint DHC - Now at a new home.....
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PostPost by: JonB » Fri Dec 29, 2017 8:10 pm

jeff jackson wrote:This is what you want...after you get now O rings, new Thackary washers, plain washers and Nyloc nuts.
Morgan Carbtune.
Easy peasy to use.
http://www.carbtune.com/

Jeff 72 +2


More money! Groan!

How do I know that I can attach them to my Dellortos? The holes are blanked off.. but with what?

Meanwhile, got the new Thakerays, O rings, washers, nylocs fitted. Has not improved matters, but at least there is the "shock absorber" effect in play. I also struggled with the timing, set it to 12 degrees BTDC but the engine's still missing (better, but not right).
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PostPost by: alan.barker » Sat Dec 30, 2017 8:19 am

I think you are looking at the wrong holes. The holes you need for the Carbtune have brass screws in.
Alan
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PostPost by: JonB » Sat Dec 30, 2017 9:39 am

Hi Alan

Could you tell me which cover you mean, please? One of these coloured rings is it... apart from the lilac coloured mixture screws :)

dellorto-key.jpg and
Dellorto key
Last edited by JonB on Sat Dec 30, 2017 10:01 am, edited 1 time in total.
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PostPost by: alan.barker » Sat Dec 30, 2017 9:46 am

Hi Jon, it's the orange ones.
Have fun
Alan
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