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 Posted: 04-25-2021 07:59 pm
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Jh092
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I recently took delivery of my new JH5 (#20092). I have spent the last couple of weeks getting familiar with it and making it road worthy. This included a new blue timing belt and tensioner bearing, fan belt, plugs, wires, etc. Also correcting some potential wiring problems from previous owners.

Now that everything is sorted out, it was time to tune the car up and drive it. Well it starts easily and idles smooth but it pops and sputters and is not smooth under acceleration. When you buy a used car, you expect that there will be some adjustments. Sorting out the carbs is not a problem if you know where to start. The first thing i was to check the jets, tubes, holders, etc to see how the carbs are set. Everything was matched across the carbs but were not the parts I was expecting. Rather than try to make adjustments to an unknown setup, I am going to set it to a spec 5 setup. That way I am at least starting at a known baseline.

As I said, adjusting the carbs is straight forward. My problem is that the rear barrel of the rear carb (cylinder 4) leaks fuel when idling and running. Enough that it runs out of the choke, drips on the starter and puddles on the block below the starter. No leak on cylinder 3 or the front carb. Kinda perplexing. It appears to be comming from the pump jet but i can't be certain. I took the carb apart and checked all the components for possible problems or damage. O-rings were in place and were not distorted, nicked, or cut. Check balls were in place. All the seats for the jets and components appeared to be good and I did not see any corrosion or dirt.

I did check the floats (8.5 gms) and adjusted them accordingly.

I am looking to see if there may be something I may be missing. If it was across both barrels of the carb or affected both carbs then it might be a little easier to diagnose. Any thoughts would be appreciated.

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 Posted: 04-25-2021 10:21 pm
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Esprit2
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Which carbs do you have? You mention setting them up to Spec 5, which is a Lotus set-up for DHLA45E carbs with 36mm chokes. However, all J-H with Dellortos came with 40mm throats and 35mm chokes... DHLA40 for the non-emissions Dellortos, and DHLA40E for the emissions carbs.

So what carbs/ throats/ chokes do you have?

Are the small metal ID tags still attached to a top cover screw on each carb? If so, what are the tag numbers?

So, gas is running out of the #4 inlet? Air is busy rushing in, yet fuel runs out?

You say all the O-rings and seals are present and in cood condition... I'll just have to take your word for that.

Check to see if the choke and auxiliary venturi are snug fits into the throat... installation may require some force. Then, is the aux venturi securely tightened into place with the pinch bolt screwed in through the carb body's outer wall, and a jamb nut?

If the Aux Venturi is not a snug fit, and if it's not tightly secured with the pinch bolt, then some of the fuel flowing down the diagonal passageway to the Aux Venturi might flow into the gap between the throat and Aux Venturi's OD, then migrate to wherever pressures take it... including out the inlet.

Let us know what you find,
Tim Engel

Last edited on 04-25-2021 10:23 pm by Esprit2

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 Posted: 04-25-2021 11:23 pm
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Jh092
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I have DHLA 45 E carbs. The DHLA 45 is cast into the cover and E is stamped after the cast number.

45mm throat, 36mm choke

Tag on rear carb r5325P

Yes, gas is visibly running out on top of throat and is not between it and the body. The throats and chokes are solidly locked in place. Had use a mallet and wood dowel to drive them out.

I have experience with a number of fuel systems but have not seen this before. Have owned a owned a twin cam europa with strombergs, currently have an elan +2 with webers and converted to strombergs, also had a tvr grantura with webers and SU's, and a turbo esprit hci with the bosch injection.

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 Posted: 04-26-2021 04:25 am
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discogodfather
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Is cylinder 4 firing ok?

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 Posted: 05-03-2021 05:01 am
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Esprit2
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You mentioned having Lotus Spec 5 carbs, but the tag number you gave is for the Lotus 911 2.2 Litre engine used in the Talbot-Sunbeam-Lotus World Rally Cars. Which doesn't mean someone in the past hasn't re-jetted them as Spec 5

FYI, here's the Sunbeam/ Lotus 911 carb specs:
5325 P. . . . Tag Number, Rear Carb --- P = Posterior (rear)
5326 A. . . . Tag Number, Front Carb -- A = Anterior. (front)
19.129. . . . Part # = DHLA 45E x 2
45mm . . . . Throat
36mm . . . . Choke
8011.1. . . . Auxiliary Venturi
158. . . . . . . Main Jet. . . . . . . . . . Spec 5 = 160
230. . . . . . . Main Air Corrector. . . Spec 5 = 230
7772.8 . . . . Main Emulsion Tube
58. . . . . . . . Idle Jet . . . . . . . . . . Spec 5 = 50
7850.9 . . . . Idle Air Corrector. . . . Spec 5 = 7850-7
60. . . . . . . . Accel Pump Jet (p/n 7851)
38V 42H . . . Accel Pump Jet (alternative) . Spec 5 = 38V 42H
95. . . . . . . . Starter Jet
7482.3 . . . . Starter Jet Emulsion Tube
170. . . . . . . Inlet Valve
7298.1 . . . . Float
10 gram . . . Float Weight . . . . . . (Alternate 8.5 gram. . Float Weight)
14.5 - 15.0 . Float Height. . . . . . . (Alternate 16.5 - 17.0 Float Height)
10.0 cc . . . . Accel Pump Discharge, cc in 20 full strokes
900-1000 . . Idle Rpm
2.0 - 3.0%. . Idle Carbon Monoxide Emissions

The float height depends upon the float weight used. At different times, two different float weights were specified, with two different corresponding float heights.

You wrote:
> I did check the floats (8.5 gms) and adjusted them accordingly.

You stated that you checked the float weight (8.5 grams) and set the height accordingly, but you don't mentioned what height you used. A 10gr float is set to 14.5 - 15.0mm, and an 8.5gr float is set to 16.5 - 17.0. If the float is set too high (smaller number) for a given weight, then the fuel level will be too high and can overflow into the throats.

However, that should affect both throats on a carb with the float set too high, and not just one. You indicate that only the #4 throat is leaking fuel, which does not compute. For a single throat leaking, I'd be looking into the fit of the auxiliary Ventury in the throat, and make certain the set screw is secure.

Regards,
Tim Engel

Last edited on 05-08-2021 12:59 am by Esprit2

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 Posted: 05-09-2021 08:23 pm
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Esprit2
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Jh092,
How about a progress report. Have you sorted it out yet?

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 Posted: 06-04-2021 12:36 am
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Jh092
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Well everything is working great and have the carbs dialed in. I dis-assemnled the cards and recleaned all of the components and passages. Reassembled them, set the mixture and idle screws to set-up settings. The car started and i was able to adjust it for smooth idle and transition to the mains. Don't know if the cleaning got out a piece of grit or by going back to base settings eliminated the problem. Im guessing that putting everything in balance eliminated whatever problem i had

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