Jetting Delorto DRLA 40 Twin Carburettors

3rd Feb 2012
My 40mm/28mm chokes had turned up from Italy and I was very pleased to see that when they arrived they were in fact the correct parts I had ordered. I had been previously trying to cure the jetting problems of my carburetors where my engine was idling well but had a lack of acceleration that could be resolved by pumping the throttle. I had believed that this was because of the size of my idle and main jets but had been told by both VW Heritage and Dellorto UK that it was more likely that my chokes being 40mm/32mm where the wrong size for my engine and was likely to be the cause of the jetting issues.

To fit the chokes into the DRLA40 carburetors is a fairly straight forward procedure, First the cross bar linkage needs to be removed . This is best achieved by unscrewing one of the ball ends that attach to the carburetor linkage plates. This has the result in making the bar shorter in length and able to be removed. The connecting rods then need to be removed from the carburetors so that it can be pulled out. You can carefully pull the bar out of the way to gain access which is the route took. To change the chokes you need to disassemble both Carburetors, it is usually safer to do this one at a time and rebuild so as not to muddle up parts. The Dellorto DRLA 40 carburetor is built up from the top . This means first the linkage bar plate needed to be removed by the four screws that held it in place. After this has been removed a gasket can be easily removed from the top of the Carburetor to expose the four inlayed bolts that hold the top of the carburetor on. Great care should be excorsied as the top plate holds the gasket and the float assembly . When separating the top from the body of the carburetor ensure that the gasket does not get trapped. It is sometimes easier in tight positions to remove the fuel line first.

With the top removed the DRLA 40 Auxiliary venturi can be removed . These are held in with two screws and a clocking nut at the front and back of the carburetor. Pictured right the screw hole with the top positioned on the carburetor . Once the nut has been loosened a screw driver can be used to undo and remove the bolt once these have been withdrawn the Auxiliary venturi pictured right can be removed. It is important to notice that the Auxilary venturi are handed and have different opposing sides . When re inserting the Auxillary venturi you must ensure the face with the o ring is positioned towards the centre of the carburetor otherwise the acceleration fuel jet will not be able to work correctly. When you have removed the Auxiliary venturi the chokes may be withdrawn from the carburetor twin barrels.


The barrels of the carburettor should look similar to the picture left. You should check the throats of both barrels are clean with a lint cloth. The 40mm/28mm chokes can then be lightly lubricated and placed back in the carburetor one in each barrel with the size stamp facing upper most . Once these have been seated . You can place the Auxiliary venturi back in the to throat above the choke it is important to ensure the rubber o ring on one side of the venturi is facing towards the main jets. With both venturi in place the securing screws can be re inserted and tightened to hold the venturi in place . It can bee seen that if teh screw does not hold the venturi tightly then the venturi is reversed and will need to be removed and fitted correctly with the o ring towards the main jets.The locking nuts can then be placed on the venturi securing screws and tightened. The top of the carburetor can then be refitted ensuring that the gasket is trapped correctly between the two parts. This can be a fiddle as there is a little spring that sits on top of the choke unit that can interfere with the refitting process. Once the top is positioned it can be re bolted back together with the four bolts. The gasket can then be placed back on top and the linkage plate can then be positioned on top with the washers , spring washers and nuts. The Air Cleaner can be re fitted and the other carburetor can then be attended to in the same way.

The linkage kit can be fitted into the linkage plate on one side and the ball joint tightened to remove any play.

Current DRLA 40 jets
Chokes 40mm/28mm Ventri
Main 112
AC 180
Emulsiontube 9164.4
Idle 60
Pumps 35

I was unable to test my new installation as I discovered that my Starter motor had failed.

Re-Jetting Carburretors and changing engine to asperated for MOT

17th March 2010
The jetting of the Dellorto DRLA 40 Carburetors was fairly simple as the main jets are easily accessible from the top of the carburetors. and can be located by removing the air cleaners if fitted.

Unfortunately one of my main jets was stuck in the left carburetor . I could remove the air corrector from the carburetor but this left the emulsion tube and main jet stuck inside the carburetor. Furthermore one of the idle jet holders in the other carburetor the idle jet holder had verdi-grease on it. I decided to remove the carburetors and do a basic clean them up.

Stuck jet stacks can be a really problem to remove and great care is required to dislodge them. I filled the jet up with carburetor cleaner and found a small screw driver that would fit snugly in the emulsion tube. I gently rocked this in its seat from site to side. Eventually this gentle movement freed the emulsion tube and main jet. This was also covered in Verdi-grease. I cleaned off the verdi-grease and replaced the jets. I had ordered new fuel line and was waiting for this to arrive so that they could be refitted.

For the 1600 I went for:
9164.4 emulsions
112 mains.
180 air.
52 idle.

MOT time looming again

28 Feb 2010
The turbo buggy was becoming a slow process again as the realisation of the fact that the engine would not fit was a major blow as I had two major hurdles to overcome before the engine could go back in.

I decided that the best option was to take the turbo modifications off and revert to the 1600 basic engine in an attempt to run the engine in and get the MOT ticket . This was annoying as I new it was going to be another year of modifications. The major of these was a 3" body lift kit. I had been asking on several websites about the Bugpack kit but had been told that it was not as strong as a box section version. This meant that I had to have one made which would take some time to be fabricated. The good thing was at least my engine would be run in prior to the fitment of the turbo. It would also allow me to fit an electric fuel pump in front of fitting the turbo and check the systems work.

After reading a for sale post open eBay for a turbo Dell IDF carburetor I was surprised to see that if it was jetted back it would still function well as an aspirated version. With this in mind I decided I needed some new jets 28 vents, 9164.4 emulsions, 112 mains, 180 air, 52 idle. Fortunately my trust box of Dell tuning parts came up with most of the parts including the 52 idle jets but no 112 main jets. I started removing the turbo and exhaust from the engine and started to clean up and paint the previous exhaust I had used. the Carplan VHT paint was fantastic and bought the exhaust up like new. I hoped the new main jets could be located soon but would have to wait to source the parts. I found the new jets and continued to paint up the rusty exhaust. There would be some fitting issues possibly with the braketry but this would have to be sorted out after fitting. I hoped my new body mount would not be obstructing the old exhaust as it had been modeled to fit the drag exhaust. The fitting or changing of the exhaust from the turbo collector was undead a problem The no3 cylinder J tube was tight on the Heavy Duty Gearbox cradle and at first would not move. This eventually came free with the help of a friend John and the next problem was also evident. The new body support I had built was right in line with this new exhaust. I decided as as I was trying to have the 3" body lift kit made that this would have to change anyway as the whole body would rise 3" making the support arms the wrong length and angle. I removed them and refitted the drag link bars that now fitted. The bracket that held the oil filter was also directly in the path of the new exhaust. I made a new bracket that placed the external oil filter lower by using the old one i had manufactured as a template. The resulting bracket can be seen left. With the bracket made I could now refit the oil filter . I now needed to start work on the electronics to run my electric fuel pump. The electric design had been given to me by a VIZI member and I was intended to fit the new electric pump I had bought with a return flow to the tank ready for the turbo to go back in.

Dellorto DRLA 40 Carburretors, Jetting and turbo application.

22nd August 2009

I had always used Weber carburettors in the past and was always hearing that Dellorto carburettors were far superior from people who had used them for years. With my new engine now progressed to the long block, I had to decide how I would supply fuel to it. Previously I had a project that consisted of a Garret turbo T3 unit and a drag exhaust that had been extended to work together. None of this had made it onto an engine and I figure that with the new strong block that I had built this would be the best time to bring it all together. With this in mind I new I could not use Weber carburettors as they could not easily be modded for turbo use. I found two Dellorto DRLA40 carburettors online in an auction that originally were from an Alfasud. I new the jetting would be wrong for the 1600 long block, but I figured that the jetting would all change with the turbo anyway so this would not be a problem. The first thing I had to do was to thoroughly clean the DRLA40's up. This is a fairly large job as it does not just entail cleaning the outside of the carburettors . The inside must be stripped down and cleaned thoroughly too. I decided this was the way I was going as I knew that ultrasonic carburettor cleaning techniques although good, would not find broken or missing parts should there be any. Once the carburettors had been thoroughly de-greased with Gunk, I started to dismantle them. The filter covers are bolted to the top of the carburettors, with this removed the top of the carburettors can be seen and access is then available to remove the top screws that hold the two parts of the carburetor together. It is beneficial as well to photograph the components before removing them so that you can easily remember were they go when rebuilding. The top will then come off the carburetor and will take with it the float which is attached to the roof of the carburetor.

I contacted John Maher Racing Ltd ; Mr John Maher in the Outer Hebrides, The isle of Harris. http://www.johnmaherracing.co.uk to ask him if he still could machine the pair of DRLA carburettors for turbo spindle seals. He told me that he still had the equipment to do this but he also said that he could not covert all Dellorto carburettors. He went on to say that you needed a 20mm boss inside the middle of the carburetor to give enough room to take the turbo seals.

He indicated that he had seen carburettors in the past that did not have this and could not be converted. Luckily my carburettors were OK and I sent them of to him. You can see the boss on the inside of the carburettor wall clearly. the picture also shows that unlike the outer bearing which is sealed. the throttle shaft runs straight onto the crab bodywork meaning that the surfaces had no seals to keep fuel in the carburettors under more than atmospheric pressure. The carburettors throttle shafts have to be routed out with a special tool that allows one side of the carburettor body to be done at a time. The picture right show the process of cutting the turbo seals. This is repeated three times for each side as three steps must be cut into the body to allow a plastic washer, o-ring and star washer to be fitted. The whole process is done from the outside of the carburetor with a cutting tool mounted on a spindle that is passed through the existing throttle shaft-hole. The cutter is also supported on the shoulder of the other side of the shaft. Some cutters have a cutting surface on each side. This actually allows the process to be simplified by pushing in and pulling out to do each of the bosses. It is imperative the recesses that are cut true to the throttle shaft .

The picture left shows the machined boss ready to take the turbo washers. It shows the three cuts made into the sidewall of the carburetor. I used the specialist services of John Mayer as I felt that he had the tools to do the job correctly. Obviously this is a risky modification to a carburetor as if the seal leaked then your whole engine could go up in flames very quickly. I ordered my turbo seal kit from Euro Carb http://www.dellorto.com and waited for my carburettors to be returned to me.

My carburettors came back very quickly and I was very happy with the machine work that had been done. I previously had stripped out everything but the throttle body as I wanted to keep the machine costs down. I knew I just had to rebuild the carburettors and had taken some good photographs of the carburettors in various states of being dismantled. The first job was to fit the new turbo seals into the newly machined areas. This seemed at first an easy job as it required fitting the washer and the o-ring followed by the star washer which was pressed into the recess to hold the washer and o-ring in place. My first attempts at this resulted in the star washer pinging back out. I decided that I would use the throttle spindle to line up the washer and o-ring so that the star washer could be pressed into place. I also used a small pair of pliers around the spindle to press the star washer from opposing sides. My patience was soon rewarded and I manged to get the four seals in place and the throttle spindle back in the carburettor with the ball race seal at each end. It is very important when assembling the throttle to match the spindle to the right carburettor side, as the spindle protrudes more on one side to accommodate the levers for the linkage system.

The butterflies could then be fixed to the throttle spindle again paying attention to the way they came out. It is important to put these in carefully as they will not fit if forced and they are very easy to bend. The rest of the carburettors could then be built up . The accelerator pumps were renewed and fitted back in. The other ancillary items where added to the carburettor and all the components where cleaned and assembled as can be seen photograph left:


At this point I had to decide what I was going to do about jetting. Fortunately I had met a gentleman Dan on Volkszone who had turboed his Beetle . He suggested that I should start off with the jetting he had as the cars had a similar specification as he had had his carburettors professionally set up. I bought the turbo conversion kits as they came with the turbo gasket and the high capacity needle valve for the float bowl.



DRLA 40 Aspirated jetting
---------------------------------

• 4x Venturis 28mm
• 4 x Main Jets  1.20
• 4 x Air corrector  1.8
• 4 x Idle jets 7644  .6
• 2 x Pump Jet 0.35
• 2 x Needle Inlet 1.5
• 2x starter emulsion tubes 7482.3
• 2x Starter Jet 60
• 4 x Emulsion tube 7212.2

DRLA 40 Turbo jetting
------------------------

• 4 x Main Jets 160
• 4 x Idle Jets 7644.60
• 4 x DRLA Pump Jet 10927 not DHLA 10927.
• 4 x Turbo Emulsion tubes 9164.turbo
• 2x starter emulsion tubes 7482.3
• 2 x starter jet 3315.80
• 2 x Air Corrector (short) 7482.170

This was quite a shopping list as the jets and emulsion tubes are only available from a few outlets. Luckily I found some CB Emulsion tubes on eBay that were better than the standard ones. I also found main jets , Idle jets an air corrector from a dealer on eBay: Fast RoadCars. The rest I would have to buy from Euro Carb. It is important to note that some parts can be shared between the DHLA and the DRLA with jets . The exception to this though is the pump jets 10927 which the DRLA uses longer versions than the DHLA.

I was very surprised how expensive the jets and the turbo conversion had cost. In hind sight It would have been cheaper to have bought one already modified but then I don't think I have seen many on the market for sale as in recent times there has been a drive towards efficiency and the carburettor has been surpassed by the injection system. This said the injection system is a whole lot more complicated and I was intending to cut my teeth on a turbo system that had a smaller number of parts to go wrong.

If you are considering doing this conversion to a set of carburettors budget at least £80-£100 for the DRLA 40 carburettors, the machining will cost upwards of £69.00 depending on how they are delivered to JMR, Turbo Conversion gaskets, seals, pump valves and other ancillaries around £96.00 without the re-jetting costs which if you may be able to source the parts from other suppliers.

I would have to purchase a new CB linkage kit for the carburettors as I knew that the CB pressure covers only fitted the CB linkage kit.

Prices current 2009 only.