Any Dellorto DHLA 45 Guru's on Here?

[Dilkris]

I have been rebuilding "on and off" a 1973 Lotus Europa Twin Cam for some years and have reached the stage of finally starting the engine - this has been a complete nut and bolt rebuild, the body is obviously off the chassis and before bringing the 2 together I thought it wise to confirm that all was OK.
My problem appears to be carb balancing/setting - these are Dellorto DHLA 45's - and my questions are as follows:-

1. The 4 vacuum points (2 on each carb) to attach vacuum gauges or manometers to appear to be accessed by simply opening the plugs (see attached photo's of said plug identified with a red arrow), to attach the vacuum tubes to but closer inspection shows that these plugs could not function as vacuum points and therefore have to be temporarily replaced during this operation - is this correct?
2. The accelerator pumps appear to be over fueling, causing excess fuel to drip from the mouths of the carbs - any ideas? (See photo and arrow of where fuel is injected into the carb from the accelerator pumps). Note: I have replaced the original mechanical fuel pump with a Facet electric pump - should I have a fuel regulator in circuit? Am I over pressurizing the carbs?
I have ordered overhaul accelerator pump kits plus float bowl needle valve assemblies as a possible solution to this problem but is it something else?

The engine starts well but is clearly running rich and I believe the carbs are out of balance.

 

[DaveB]

There are several types of Facet brand fuel pump so it would help if you were a little more specific, but I'm assuming you mean a high volume interrupter type.

Rated pressures are ;
solid state type 3.5 psi
silver top 5 psi
red/blue top 7.5 psi

The interrupter types are too strong for most carbs, where you generally need only 2 psi, but that is a fuel flowing value not static.
THe DHLA might work well with a bit more pressure, maybe 3.5 psi.
Watch out for vibration shaking the carb and unseating the float valve,

You probably need a regulator, like the Malpassi Filterking.

 

[northwest]

For authenticity's sake the Dellortos definitely but I would put it on Fuel injection and a simple engine management system. Improves reliability and running no end.

 

[Dilkris]

There are several types of Facet brand fuel pump so it would help if you were a little more specific, but I'm assuming you mean a high volume interrupter type.

Rated pressures are ;
solid state type 3.5 psi
silver top 5 psi
red/blue top 7.5 psi

The interrupter types are too strong for most carbs, where you generally need only 2 psi, but that is a fuel flowing value not static.
THe DHLA might work well with a bit more pressure, maybe 3.5 psi.
Watch out for vibration shaking the carb and unseating the float valve,

You probably need a regulator, like the Malpassi Filterking.

Thanks Dave - Fair comment - please see attached photo - I believe it to be solid state unit.
Note this is a temporary fuel set up..!!! But the pump itself won't be.
Possibility of a regulator required noted - originally the motor runs a mechanical fuel pump.

 

[dobbslc]

What is the arrow pointing to in the bellmouth?

 

[Dilkris]

For authenticity's sake the Dellortos definitely but I would put it on Fuel injection and a simple engine management system. Improves reliability and running no end.

Agreed - if I had a money tree I would consider it
Authenticity is a big thing with these cars though.

 

[Dilkris]

What is the arrow pointing to in the bellmouth?

It is pointing to where the fuel from the accelerator pump enters the throat of the carb.

 

[Nomad]

Hi. No experience with Dellortos but spent a lot of time with Webbers etc from the same era.

Do the screws have a hole cross-drilled near the tip (like a brake bleed nipple?) - if so remove the screw and check the drilling isn't blocked. I've seen some where you unscrew the bolt a few turns then slide the tube of the head.

A vacuum balancer makes setting up a lot easier, I use a 4-way Carbtune kit.

Check the workshop manual for the injector pump, they often have a ball valve and a loose "restrictor piece piston" that controls how much is delivered, easy to miss the bits out then you get over-delivery.
I normally remove the ball & restrictor then blow out all drillings with carb cleaner or WD40 to make sure no blockages.
My new thing is to soak all jets in a white vinegar solution to soften old varnish then use a nylon or brass brush to freshen them. Then blow though to clean debris ..
Some later carbs had adjustable linkages to the pump so you could alter the amount delivered but I wouldn't expect on yours.

Fuel pump - depends which Facet pump you have. I'm using a 3psi Facet on a 1970s (single carb) motor and it works fine. If you have a higher spec pump, a filter / regulator would be sensible.

Check the fuel level in the carb. I've had a few where it was too high, also had others (Kawasaki 1100 !) where the fuel level was at the top end of the factory spec and it ran rich, dropping it to the low end of the spec it ran great.

Sounds like a fun project, photos are always welcome

 

[Dilkris]

Do the screws have a hole cross-drilled near the tip (like a brake bleed nipple?) - if so remove the screw and check the drilling isn't blocked. I've seen some where you unscrew the bolt a few turns then slide the tube of the head.

A vacuum balancer makes setting up a lot easier, I use a 4-way Carbtune kit.

Sounds like a fun project, photos are always welcome

Many thanks your reply.
Please see photo's of said screws in my original post - there is no through drilling as I expected. Have poked around with nozzle cleaners. I equally expected them to function as per your description - they don't.
I agree re vacuum balancer - but reluctant to spend £50 for something I will use for 5 minutes just once...
This project over the years has hemorrhaged money

 

[Nomad]

Most odd - the factory have gone to the trouble of making a center drilling in the screw (where the screwdriver fits) but it sounds like it goes nowhere and does nothing.

Hope you get it sorted

 

[lazybones51]

Many thanks your reply.
I agree re vacuum balancer - but reluctant to spend £50 for something I will use for 5 minutes just once...
This project over the years has hemorrhaged money

Might be able to pick one up used, or buy new and sell it on. I picked one up used on eBay to balance bike carbs. Seems to still be a demand for them in the bike world.

 

[8ob]

Seems like a big carb for twinky 1558, messed with these for a few years and even the tuned one I had managed well on 40s choked down to 33mm.

Bob.

 

[Blobber]

I have got the proper Dellorto manual somewhere if you want me to have a rumage, also got a carb balancer that you poke in the bell mouths if you want to borrow that

 

[Dilkris]

Might be able to pick one up used, or buy new and sell it on. I picked one up used on eBay to balance bike carbs. Seems to still be a demand for them in the bike world.

Do you want to sell it cheap...???
Lots of DIY manometer set up's on Utube - so I'm tending to go that route.

 

[Dilkris]

Seems like a big carb for twinky 1558, messed with these for a few years and even the tuned one I had managed well on 40s choked down to 33mm.

Bob.

There are 2 of them as well .....

 

[Dilkris]

I have got the proper Dellorto manual somewhere if you want me to have a rumage, also got a carb balancer that you poke in the bell mouths if you want to borrow that

Now that would be very useful - let me see how I get on before I start asking you further about this. Many thanks.

 

[Blobber]

Do you want to sell it cheap...???
Lots of DIY manometer set up's on Utube - so I'm tending to go that route.

I run Dellorto 48s on the Viva so no I dont want to sell it

 

[Dilkris]

Most odd - the factory have gone to the trouble of making a center drilling in the screw (where the screwdriver fits) but it sounds like it goes nowhere and does nothing.

Hope you get it sorted

My thoughts entirely !!!

 

[DaveB]

Thanks Dave - Fair comment - please see attached photo - I believe it to be solid state unit.

Certainly looks like the solid state pump.

Long time since I played with a dellorto or weber.
From memory the accelerator pump has a spring on the linkage, and a jet on the outlet.
You have to find a balance between the spring strength and the jet size to give the correct pump action.
I assume you mean the fuel comes out the inlet when the engine is running ? is this at idle or from part throttle ?
I suggest leave it until you can get it tested under load on a rolling road. Trouble is finding an old school rolling road and someone who understands the carbs. Maybe Aldon Automotive is your closest.

 

[Dilkris]

Certainly looks like the solid state pump.
From memory the accelerator pump has a spring on the linkage, and a jet on the outlet.
You have to find a balance between the spring strength and the jet size to give the correct pump action.
I assume you mean the fuel comes out the inlet when the engine is running ? is this at idle or from part throttle ?

Yes - the accelerator pump mechanism is an arrangement as you describe - and yes it would be adjustable as you equally surmise.
Yes - fuel drips out of the inlet trumpets if I "blip" the throttle - it seems the accelerator pumps inject too much volume of fuel.
At idle, with the accelerator pumps not operable and dormant so to speak - all is good.