Carbs, Plugs and Fuel.

[Aleco]

Ever since I converted my sprint to Dellortos I done think the fuelling has ever been fully spot on.
The initial set up was horrendous, the smell of fuel could have knocked you out after 2 minutes in the car!
I had a the car set up on a rolling road by a local specialist and it transformed the car.
That was about two years ago. The car has been running well but still a little 'petrolly' occasionally. Which I just put down to running the bigger carbs.
I've got the car back running after a taking it off the road for a trackerjack conversion which took a while due to other commitments.

Anyway, the car still pulls well at higher revs but is flat and a bit farty low down and the smell and taste of petrol has returned. Not as bad a previously but enough to make a long journey unpleasant.

Do anyone with Dellortos/Weber's have the same issue? Is it a feature of the product? I've also noticed the oil is starting to smell of petrol.

I did a bit of digging about on the forum and had the realisation that it could be the plugs. I've ordered a new set of NGK BP6EFS's and will change as soon as they're here
I'm currently running Bosch HR7DCX plugs. I didn't fit them, I'm not entirely sure if the garage I use occasionally fitted them.
Anyway, I pulled a plug and it looked ok. Not a perfect biscuit colour but serviceable. The gap is 35 thou which seems a little large.

Does anyone have any thoughts or suggestions? Would the incorrect/old plugs cause the symptoms above?

Does it need another session on the rolling road? I thought that Dellortos/Weber's were (relatively) fit and forget once set up correctly.

Any info or guidance would be greatly appreciated.

Alex

[dollyman]

Those plugs are running fine Alex, i would suspect the carbs are the problem. Dellorto's were always troublesome as they were Weber's poor cousin The Weber's are pretty much fit and forget and are a much better unit.
Is the oil level rising at all? As it could be down to the fuel pump or are you on electric? Maybe another trip to the rolling road is in order? Or put the money towards a set of Weber's. Just my thought having used both in the past.

Tony.

[Mad Mart]

I would say 35 thou is to big a gap, standard is 25 thou. But I don't know about the Bosch plugs so maybe they are ok with a bigger gap.

[cleverusername]

Did you set these up yourself or get a professional to do them? I have looked into these sort of carbs and the consensus seems to be, that you need a rolling road and an expert to set them up properly.

Twin SUs are a lot easier for a home mechanic to setup properly.

[Aleco]

They were set up on a rolling road by a professional. I'm thinking of booking into Airey to have another set up but I wanted to ensure that I wasn't missing something obvious.

Mart: Yes, I think the gap is a little large. Will go for 25 thou on the NGK's .

Dolly man: I'm running a pacet electric pump with a regulator. The oil level hasn't gone up that I can see just smells a little like petrol.
I thought Dellortos were better than Weber's? That seemed to be the consensus on the research I did before buying them. I don't have any real life comparisons just what I had read.

[dollyman]

I was just going off what was being used in the rallying scene in the 70's and 80's Alex. Dellorto's you could buy for peanuts as everyone wanted the Weber's. I tend to keep my cars bog standard now I think it's called "getting old"
I never tend to go off articles about anything these day's, i just go off personal recommendation Maybe i should have kept the many Dellortos that i binned back in the day.
Good luck with them though.

Tony.

[MIG Wielder]

Hi , You are probably aware of most of these comments below, but I hope my experiences are useful anyway. I assume you have DHLA45-E ?
I have a pair of Dellorto 45s on the Lotus. Yes they are a lot more complex than the twin SU Sprint set up, but they just work and don't need much looking at between services. They shouldn't smell of fuel. That is not good news. The first thing I'd do is have them off the manifold and replace the floats and needle valves. The needle valve operating tab does wear and develops a little wear pip after a high mileage which causes it to stick.

Then there is a setting up procedure which will be in the manual.

Its q bit odd that the plugs don't look sooty but the car smells of petrol

I suppose you have a suitable air-box with a breather to the cam-cover to get rid of oil / petrol fumes ?

Now I've seen many modified Lotus set-ups with open trumpets etc; etc; but they never seem to work as well on the Lotus.

What jets do you have currently ? This is the complex part with 16 jets to be cleaned at each service. And yes, do run with a good fuel filter. Its cheap insurance.
A standard Sprint fuel pump should be fine for the Dellortos. Lotus have an S.U. lekky pump which works well.

For setting them up I use a Gunson's Carbalancer. The best bit of the Dellortos is the clever differential throttle balance screw. A nice bit of design !
For mixture setting I use a Colourtune. Ooooh yes if you clean off the mixture adjusting screw needles and replace the seals it makes setting up much more predictable.
And when it comes to the emissions for the MOT the car runs quite happily at 1.8% CO.

And check the accelerator pump works O.K. There is a setting procedure for this in the manual.

Like you , I used to have problems at low engine revs; on acceleration. Changing the idle jets cured that. But clean out the progression holes as well.

Re-attaching the carbs; to the manifold also has a procedure to avoid cracking the castings. Use new gaskets.

And yes, hot starting can be a problem in the Summer. The recommended way is to floor the throttle, hold it there and turn the engine over until it fires.
The Dellorto Agents are ( were ?) somewhere near Reading in Berks; they are very helpful. Parts are expensive though.
The fuel banjo units into the carbs do work loose and on the Lotus the leaks are BAD news. You need a torque wrench on these. There is the standard story of the Elite owner going into the specialist and asking if they have a solution to the banjo bolts working loose ….
"You haven't got a Lotus have you….. ? "

HTH,
Tony.

[Aleco]

Hi Tony,
Thanks for taking the time to give such a detailed response, it’s appreciated.
Yes, I’m running 45 – E's.

I was thinking about the float and needle valve but the carbs are reconditioned units from Eurocarb with less than 2k miles on them. Eurocarb are the UK agents you mentioned.
I’ll give them a call and see if they have any advice.

To give a bit more detail, I put the car in the garage Monday and went in Tuesday and had a really strong smell of petrol again. It might sound weird but I went round sniffing the carbs and found the smell was very strong from the top of the carb. From the choke intake vent/port?

I don’t have an airbox just K+N filters. Would an airbox make a big difference?

I don’t know what jets etc I’ve got fitted I pretty much left that to the chap doing the rolling road set up.
I do run a filter and change it regularly.
And I've already fallen foul of the banjo working loose! Had a panicked few moments as I saw petrol pour down the side of the engine!

Alex

[MIG Wielder]

Hi Alex, Thanks for the update. I used to know the Dellorto place as Contact Developments ; I did find the web-site and it looks as if they have merged now and moved to Pangbourne. Yes, since they have reconditioned the carbs; the floats etc; should be good and the workmanship will be of a high quality, with all the parts back-up on site. A good start.

I think there may be a clue in where the petrol smell is.
Do you have an actual choke linkage back into the dashboard ( with the link-rod across the tops of the two carbs; ) or do you rely on 2 presses of the throttle pedal when doing a cold start ( to activate the accelerator pump ) ? If so, is that choke linkage closing O.K. It's the quarter turn cam on the tower with the brass plug on top. If this cam is turning and closing O.K. I suppose it could have come disconnected from the mechanism inside the tower, but it would mean the choke was open all the time. But I would have thought you would have sooty black spark plugs.
If you have the sectioned diagram of the carbs; on page 61.1.31.29/1 (!) the float chamber is vented to the outside through the vent Item 4 and 5 which is also the plastic nylon jet cover. As you say, the vent port. I imagine this is where the smell is strongest. If the choke was open the vapourised fuel in the drillings to the engine side of the throttle disc would be all around here. I would have another look at this area perhaps ?
The reason that Lotus have this airbox ( so the legend goes) is because the Lotus engine is inclined to spit back and chuck neat fuel back out of the trumpets. So Colin Chapman decreed that the whole intake side would be enclosed in a fireproof box with a long duct to the nearside. I don't think I've ever had mine spit back. It also provides somewhere to vent the crankcase to.
I think a Colourtune might tell you a bit more; but with the plugs being reasonable I think a chat with Eurocarbs technical people may also help.
Good Luck with it,
Tony.

[gmsclassics]

I ran 45 Dellortos for over 20,000km on the brown Sprint I raced. I got them secondhand off a Ford Escort and had them professionally cleaned and rebuilt. They were jetted initially as per Lotus Excel spec and subsequently the idle jet was enlarged a bit on testing, rather like Tony’s comment. Never had to change anything, nor rebuild / overhaul. Probably the most reliable part of the car! Never had any leaks, nor smell of petrol.

However I do remember others who raced on Webers and Dellortos having issues with high pressure pumps and pressure regulators. I used the simplest and cheapest low pressure pump I could find. Always enough fuel, even over 7000rpm, but never too much.

No choke, just pedal twice to the floor before turning the key and it started everytime, cold or hot. I used K&Ns to start with and later just individual large red sponge filters. No issues with either.

I did run BP7EFS plugs with a 30 thou gap with electronic ignition (Magnetronic) which was the advice I was given and seemed good. For the road the ‘6’ plugs should be best.

Sounds to me that Tony’s comments are correct, too much fuel but not going though to the engine as plugs are fine.

Hope you find a solution soon
Geoff