Lotus Elan

Dell Orto carb service after head gasket replacement

PostPost by: pimkeirle » Wed Dec 29, 2010 12:54 pm

I am just carrying out a head gasket replacement on my +2S 130/5. As per workshop manual, I have removed the head complete with carbs. The carbs were completely rebuilt 10,000 miles ago and the car was running really well with good performance and economy prior to head removal - I have only carried this out because I have noticed that the radiator pressurises slightly after starting up, and the car had started to use a little more water than it used to ( I can now see a couple of places on the gasket that show water staining) I am tempted to leave the carbs alone on the principle of "if it ain't broke, don't fix it". What do other owners think, should I get them rebuilt anyway while they are off the car, and if not, will I fatally disturb anything when I turn them upside down to clean up the head?
Any advice welcome as I am a total novice with elan engines. Total mileage is 79,000, engine rebuilt at 52,000. carbs re-built at 69,000.
pimkeirle
First Gear
First Gear
 
Posts: 20
Joined: 08 Aug 2007

PostPost by: alaric » Wed Dec 29, 2010 4:29 pm

Hi. If the car was running fine then I can't see why you'd need to rebuild them now. Personally I'd leave them alone. I'd probably go through the full set up procedure once the head is back on. I have a carbtune II 4 column manometer that screws directly into the barrels of the Dellortos, and shows how well the carbs are balanced. Using this and setting up the mixtures following the procedure in Des Hammil's book (http://www.amazon.co.uk/Build-Power-Del ... 1903706750) got my engine running nicely.

All the best.

Sean.
alaric
Fourth Gear
Fourth Gear
 
Posts: 900
Joined: 07 Apr 2005
Location: South Dorset, UK

PostPost by: hartley hare » Thu Dec 30, 2010 2:21 am

agree with above,about not rebuilding them,as for any damage when turning them upside down,this shouldnt cause any problems,but you will find it easier to set ignition timing with front carb off anyway....
so might as well remove them,and make handling the head easier, plus you can check o rings while your at it....

good luck...
User avatar
hartley hare
Second Gear
Second Gear
 
Posts: 73
Joined: 13 Oct 2010

PostPost by: Esprit2 » Thu Dec 30, 2010 7:23 pm

There's no compelling reason to rebuild the carbs now if they were running well before the head was removed. It would be easier now, if you choose to do so, but it's optional. Modern oxygenated gasoline is nasty stuff in terms of leaving deposits in the carbs. If nothing else, this would be a good opportunity to go through the carbs and clean them up. But still optional.

The chances of removing one or both, and re-installing them without disturbing the balance are nil. If you have the tools and know what you're doing, re-balancing is no big deal. If you paid someone else to set up the carbs correctly, then you'll be throwing that away by removing carbs and/or messing with the linkage coupler.

A 4-tube manometer is the best tool for balancing Dellortos, and IMHO, the Carbtune II is the best 4-tube manometer. Not cheap, but worth the money.

Regards,
Tim Engel
Esprit2
Third Gear
Third Gear
 
Posts: 371
Joined: 02 Apr 2008
Location: Twin Cities, Minnesota, USA

PostPost by: billwill » Sat Jan 01, 2011 3:50 pm

>The chances of removing one or both, and re-installing them without disturbing the balance are nil

I disagree.

The coupling between the two Dellortos is spring loaded, and it is relatively easy to take off the front carb without upsetting the setting of the balance screw. So provided that the o-rings are in good condition and you put the carbs back where they were without altering any of their adjustors, and change in balance will be minimal.

To put it back you push the spring-loaded portion of the balance adjustor (without rotating the screw at all) and it slips over the 'blade' of the rear carb. You have to 'open' the throttle of the rear carb about a quarter to do this.
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4724
Joined: 19 Apr 2008
Location: London UK

PostPost by: Esprit2 » Sat Jan 01, 2011 9:01 pm

billwill wrote:The coupling between the two Dellortos is spring loaded, and it is relatively easy to take off the front carb without upsetting the setting of the balance screw. So provided that the o-rings are in good condition and you put the carbs back where they were without altering any of their adjustors, and change in balance will be minimal.

To put it back you push the spring-loaded portion of the balance adjustor (without rotating the screw at all) and it slips over the 'blade' of the rear carb. You have to 'open' the throttle of the rear carb about a quarter to do this.

For someone practiced at R&R'ing the carbs, it's possible to do the job as you describe. Sometimes not. For someone who has to ask the question, their experience doesn't bode well for success.

The carb mounting studs are long enough that the necessity to slide the carb back off them conflicts with the need to first slide the carb sideways to disengage the coupler. The compromise twist-it-out can put some stress on the coupler bits... both going off and on.

Depending upon where the coupler is in it's range, there may not be enough freeplay to allow the coupler to disengage without stressing something. The better move for the sake of the parts is to back off on the coupler in order to free up all the available slack before removing the carb. The even better move is to remove both carbs together, then slide the coupler apart afterwards.

Beyond that, we'll just have to agree to disagree.

Regards,
Tim Engel
Esprit2
Third Gear
Third Gear
 
Posts: 371
Joined: 02 Apr 2008
Location: Twin Cities, Minnesota, USA

PostPost by: billwill » Sun Jan 02, 2011 4:47 pm

MMM, yes, come to think of it, you do need to undo the securing nuts of the rear carb as well, so that you can pull both to the point where you can get the front carb clear of the studs.
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4724
Joined: 19 Apr 2008
Location: London UK

Total Online:

Users browsing this forum: No registered users and 5 guests