Lotus Elan

Dellorto DHLA Needle Valve

PostPost by: andyelan » Thu Feb 03, 2011 3:17 pm

Hi Everyone

I wonder if anyone here might be able to help

I have a '73 Plus2S 130/5 fitted with the standard Dellorto DHLA40 carburettors. Although the car generally runs ok, it has always seemd rather thirsty and also gets quite wet inside the inlet box so I've just taken the carburettor tops off with the intention of checking the float heights.

What I've now found is that the floats are set to nothing like what it says in the Workshop Manual, but most significantly, there are two seals under each of the needle valve seats. I assume this is incorrect (presumably a mistake by a previous owner) and there should only be one, however, I just wondered if anyone else had any thoughts on the subject or knows anything different.

Regards
Andy
andyelan
Fourth Gear
Fourth Gear
 
Posts: 555
Joined: 28 Feb 2008

PostPost by: terryp » Thu Feb 03, 2011 3:42 pm

Andy
Were the floats set too high or too low?
Mine have only one aluminium type seal. I also have fitted Viton tipped needle valves which is a good idea as they seal better. The two seals may have been a fix for worn needle valves?

Terry
terryp
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1670
Joined: 29 Nov 2007

PostPost by: types26/36 » Thu Feb 03, 2011 3:49 pm

Andy, maybe the fitting of the two seals (washers?) were not so much of a mistake but more of an attempt by the PO to alter the float level? I seem to remember with some carbs (maybe Solex???) that adding or subtracting washers is the recognized method of float adjustment.
I would suggest you put it back to Lotus specs and go from there.
http://www.lotuselan.net/publish/lsb_de ... dhla.shtml
Brian
64 S2 Roadster
72 Sprint FHC
User avatar
types26/36
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 3655
Joined: 11 Sep 2003
Location: U.K.

PostPost by: andyelan » Thu Feb 03, 2011 4:07 pm

Hi Brian and Terry

Thanks for that, I do think this was someones attempt to cure a flooding problem. The floats were set too low (ie the setting dimension was too large at 19.5 mm)

The thing is, I never just like to accecpt that mistakes were made with understanding the reasons why. I this case the fact both carbs were the same suggests this was done deliberately and there was some logic behind it even if that logic was incorrect. It is now my intention to put things back to standard with a new pair of viton needles

Regards
andy
andyelan
Fourth Gear
Fourth Gear
 
Posts: 555
Joined: 28 Feb 2008

PostPost by: terryp » Thu Feb 03, 2011 4:36 pm

Andy
In the manual from memory there are two settings, normal and one for when the carbs are continuously flooding. I set mine to the later and it seems fine.
Terry
terryp
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1670
Joined: 29 Nov 2007

PostPost by: Esprit2 » Fri Feb 04, 2011 8:46 pm

I can't say why someone would have shimmed the inlet valves out with washers, unless they were bringing some old Solex habits to their Dellortos. But I do believe the best solution for you is to go back to stock, install new inlet valves and set the float heights to stock spec.

Viton tipped needles work great, but the rubber tip will take a compression set shortly after installation. If you use rubber tipped needles, install them quickly, and then let them set for a few days with fuel in the bowls. Then go back in and take your time properly setting the float heights. If you don't do that, the float height will drift from your perfect setting toward something higher as the needle tips take a set.

Inlet valves are sized, a little like jets. Be sure you use the correct size, per the specs.

Dellorto floats come in several weights, and there's a different height setting for each weight. If you change weights, you must change heights in order to produce the correct fuel level. The weight is marked on the float, so be sure to compare that to the specs prior to setting the float height.

The basic Dellorto part number for the floats is 7298-99-_ _ with two final digits for each specific weight:
01 = 10 gr
02 = 8.5 gr
03 = 7.0 gr (no longer available ??)

The service bulletin linked in a message above covers two different carb set ups, not optional set-ups for one carb. Do not mix and match. Having said that, if one replacement float is unobtainium, then use the other along with the height recommended for it. You may have to tweak from there, but that combination will produce a workable fuel level.

Regards,
Tim Engel
Lotus Owners Oftha North
Esprit2
Third Gear
Third Gear
 
Posts: 386
Joined: 02 Apr 2008
Location: Twin Cities, Minnesota, USA

PostPost by: bill308 » Fri Feb 04, 2011 11:43 pm

Tim,

Can you tell me which is the most common part numbers/weight for Lotus applications, especially the Elan?

Bill
bill308
Fourth Gear
Fourth Gear
 
Posts: 781
Joined: 27 May 2004
Location: Windsor, CT USA

PostPost by: Esprit2 » Sat Feb 05, 2011 12:54 am

From the Lotus Service Bulletin linked in Brian's message above:

Lotus Service Bulletin
Class ...... 111
Number ... 1973/10
Type ...... All models
Date ....... 02.04.73

Title: ...... Dellorto Carburetters - Type DHLA 40 and DHLA-E 40.
Reason: ...To inform Dealer personnel of the recommended revised float level adjustment.
Action: ... This information supersedes that already published in Section V (Fuel System)
.............. of the Workshop Manuals.

Two float assemblies are currently used in Dellorto carburetters, these being:

Dellorto DHLA 40 (non-emission) carburetter
Float Ass'y: 7298-01 (A036 E 6061Z)
Float Level: 14.5 to 15 mm ... (0.571 to 0.591 inch)

Dellorto DHLA-40E (emission) carburetter
Float Ass'y: 7298-02 (A036 E 6062Z)
Float Level: 16.5 to 17 mm ... (0.650 to 0.669 inch)

Check your carbs. DHLA40 or DHLA40E will be cast into the carb body, on top of one of the barrels.

To check the float level, the whole cover assembly is held on edge with the floats hanging down and the needle valve only lightly closed (ie, light contact). The gasket must be in place on the cover... measure from the float to the gasket face, not to the cover's metal face.

Regards,
Tim Engel
Lotus Owners Oftha North
Esprit2
Third Gear
Third Gear
 
Posts: 386
Joined: 02 Apr 2008
Location: Twin Cities, Minnesota, USA

PostPost by: andyelan » Sat Feb 05, 2011 5:30 pm

Hi Everyone

Thanks very much for all the suggestions. I think it confirmed what I already expected which was best to return everything back to the standard settings.

The carbs are DHLA40 and they do have the correct 10g 7298-01 floats, so I've set them to exactly 15mm and fitted new viton tipped needles. I expect this will have affected the slow running mixture settings but I'll look at that tomorrow.

The thing is, although the engine has never been quite as sweet as the one in my Europa (that has DHLA40E which I know are set up correctly) the car has never really run too badly. It has always been very difficult to start in very cold weather which I imagin could be down to the low float level, yet on the other hand, fuel cosumption has always seemed to be rather high and it's always been wet inside the air box and that to me would suggest a high float level. My only thoughts are that the needles may have been leaking and the previous owner had attempted the cure this by lowering the float levels instead of fixing the root cause. If this were the case, then I guess the fuel level in the carbs could have been anywhere.

Once again thanks for the suggestions

Regards
Andy
Last edited by andyelan on Tue Feb 08, 2011 1:41 pm, edited 2 times in total.
andyelan
Fourth Gear
Fourth Gear
 
Posts: 555
Joined: 28 Feb 2008

PostPost by: elancoupe » Tue Feb 08, 2011 11:33 am

Mike
elancoupe
Fourth Gear
Fourth Gear
 
Posts: 995
Joined: 11 Sep 2003
Location: Spam-on-Rye

Total Online:

Users browsing this forum: No registered users and 3 guests