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 Dellorto emulsion tubes 
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Joined: Mon Jun 10, 2013 9:37 pm
Posts: 16
Hi guys, haven't posted in a long time. Mostly lurking. I have a Jensen Healey with Lotus 907 and Dellorto 45 DHLA.
My question: is it advisable to try to modify the emulsion tubes to alter the curve or just buy replacements?
Any info or opinion is appreciated.

Fri Dec 23, 2016 2:06 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
Whether point B can be reached from point A would depend on the present tubes and intended goal. Can you be more specific. Do you have a WBO2?

How did the 750 turn out?

Fri Dec 23, 2016 5:35 pm

Joined: Mon Jun 10, 2013 9:37 pm
Posts: 16
Thanks for the reply Tuner....I thought about my question after I posted iit and realized it's pretty vague. I actually haven't even put the LM 2 on it yet so I'm kind of ahead of myself. I will say that the way it's set up spark plugs were good for about a half hour and throttle response is pretty soggy. I've put smaller idle jets in it and a thermostat so at least I can start it when I need to.

As to the 750, I read every post I could find from you and Mr. Whitener, and it turned out fine. Although I saw a post somewhere where you were fighting with a Holley that had a low speed cruise flat spot in it and you cured it by closing the secondary and I think you drilled the butterfly. Mine did the same thing, wouldn't respond to accelerator pump changes, but it did respond to bigger main jets [74 instead of 72, flat spot was in the 40 to 45 mph area when trying to change lanes or go by a slower car], now I want to try your method and see if I can use smaller jets....
Thanks for the help.
I'll post back when I have something intelligent to add[that could actually be never though]

Fri Dec 23, 2016 8:16 pm

Joined: Mon Jun 10, 2013 9:37 pm
Posts: 16
for purposes of conversation, this is what I found in the Dellorto:
36mm choke
7850-9 idle jet holder
58 idle jet
7772-7 main emulsion tube
158 main jet
230 main air corrector
60 accelerator pump jet
95 cold start jet
all on a very stock Lotus 907 with a cast iron exhaust manifold and sooty black plugs
the booster looks like a straight leg Holley, only longer

Fri Dec 23, 2016 8:46 pm
Site Admin

Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
I have a Des Hammill book about Weber and Dellorto carbs which has some suggested calibrations for other ~ 2L engines but not specifically for the Lotus 907. The MJ associated with 34MM venturi is in the 140-145 range with 180-200 air corrector, accelerator pump jet in the 40-45 range. Your idle jet is near same as these 50-55. The engines mentioned are 2L Pinto, 16V Vauxhall and 2L Ford Sierra Cosworth. So, if that book is any indication, why is yours jetted so rich? Do you have the original calibration specifications? You probably already know about the Jensen Healey site here and there must be more somewhere.

Sat Dec 24, 2016 12:52 am

Joined: Mon Jun 10, 2013 9:37 pm
Posts: 16
Thanks for your interest. I went and got a copy of that Des Hammill book myself.
So far I've been able to get the cold start system working well, took out the 95 jet and started with a 45 that I ultimately drilled to .027". Works beautifully.
Changed the chokes to 34mm. Car runs and drives well, plugs have cleaned up from driving.
I changed the low speed jet to a 50, using the same idle jet holder. Idle screws are 3 turns out, idles smoothly at 950. Actually runs really well. Changed the accelerator jet to a 40 or 42, don't remember right now.
My current issue is at about 2800-2900 rpm there is an almost imperceptible miss. You can just hear it in the exhaust, very "light" pop, and a barely "feelable"[is that even a word] vibration coming through the car. This goes away if you accelerate through it, so I believe the mains start then.
My question; Is it worth trying to tap the idle jet holder for a set screw and trying to restrict the air through it, or, try using a stainless guitar string to restrict the air [I would need suggestions on a diameter to start with] or just capitulate and drill the idle jet bigger? I know I could just change the holder, but I would be guessing as to which to choose....

Car has 32* timing total, about 16* initial, and I bought a vacuum advance can [10*] to replace the factory vacuum retard. Manifold vacuum.
Thanks for you opinion

Fri Feb 10, 2017 11:46 am
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