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 Once the nut has been loosened a screw driver can be used to undo and remove the bolt once these have been withdrawn the Auxiliary venturi pictured right can be removed.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.

A New lease of Life

16th January 2011

I returned to the garage today after purchasing a new battery with 420 amps of starting power in an 63 battery format. I had a great deal of problem explaining to the retailer that this was a heavy duty version of the 63 format and was available . He spent quite a wile trying to tell me all the 63 format batteries where only 330 Amp stating current until he found one on his shelves. :-)

My Perseverance was rewarded as i returned to the garage and found that the battery indeed turned the engine over much better. The engine however would still not start and there appeared to be a lack of significant ignition. I removed the distributor cab and looked and the point working with the ignition in first position. The spark was very week and fragmented. I decided that I would need to replace them and managed to purchase a set from my GSF store along with a new condensor . I put this into the distributor and set the points on the square of the distributor shaft too .016". I put the distributor back in the engine and connected up the ignition leads . I noticed my no 2 cylinder spark plug was not tight so places some oil on it and tightened it up. I then ran up the engine:




The most noticeable thing was the engine speed was very high. I would have to look at this another day as my throttle was not returning as it should allowing the engine to idle. I was not sure whether I needed to lengthen the throttle cable unscrew the stops or fit stronger springs.

On the whole I was very pleased with the day as my new battery was much better and the points and condensor had only set me back £6.00.

Next time I would try to get the Idle speed down to a better tick over and see if the buggy still had its acceleration problems that had dogged me last year.

Battery, No reason for not starting

13th January 2012

The troublesome Friday 13th had arrived for some but this year I was given a lovely surprise and thus has become a lucky day for me for different reasons and is certainly one i will be noting in my diary.

Since my new year visit to my garage I had been experiencing problems with my battery not providing enough power to start the car and turn over the engine . I had wondered if this was because of the high compression with the new 1641 Barrels and Pistons. However in these austerity times, needs meant I had to locate a battery from a different source I had not realized although I had bought a higher amps battery that although it was a 60 amp battery it only had 335 amps of starting current( As seen in the picture above.). I was researching higher Capacity batteries and discovered quite by accident that most VW Beetle batteries where rated at 420 amp starting current or even 440amp. This clearly was the problem as I had more resistance due to higher Psi in my heads and a weaker starting capacity.

I rang my local dealer and he told me the Bosh 63 batter was rated at 44 amps with a starting current of 440amps . I would have to buy a different battery to solve this.

I also turned the buggy round in the garage so I could get better access to the engine.

2012 New Year

2nd Jan 2012

I wish to say happy new year to the readers of my blog . Not much activity or time has been spent on the buggy in the last couple of months as the weather has been seasonal and not permitted it. I ventured up to the garage today as the weather was fresh and sunny. I took the dust cover of the car and checked the car over. The fuel pressure was not showing on the dial so I new that the buggy was not going to start today. I hooked the car up to the buggy battery with jump leads and ran my car to ensure the battery had a stable load. Electrics and fuel do not ever seem to like coming through the winter . I turned the ignition over several times until I got the fuel pressure gauge back up to 3 psi . The buggy still would not start. I used some Carburettor cleaner down the throat of the Carburetors and tried again . Eventually the Engine started to fire. However I the engine stopped firing and the battery started to take a beating. With the fuel back up to its pressure I decided to leave the buggy for a day for the fuel to permeate the carburetors and free up the gantries.

I would try again on the next available day.

Engine faltering under acceleration

22nd Nov 2011.

I fitted the electrics to the rear of the buggy using the coiled wire protectors I had purchased . This gave greater protection to the wiring . With the engine rebuilt I still been having problems with acceleration that had been dogging my new engine for some time . I had tried replacing engine parts to solve this but to date had had little success. The problem was still alluding me and several friends could not resolve this problem either. It had been a busy month with other activities so I was unable to spend as much time as I wanted to.

I replaced the fuel pump with a new fuel pump regulator and pressure gauge in an attempt to see if there was a fueling issue that was preventing fuel reaching the twin carburetors. The fuel pressure was correct and providing 2.5-3 psi on the gauge. I pressure tested the heads and they all came out the same over 980 lbs on each cylinder suggesting I had good compression.

I tried swapping the distributor to see if my 009 distributor was failing this did not improve the situation.

I know I am running 32 Venturi in my DRLA carburetors and am now wondering whether my poor running is because of this ? I rang VW Heratige who told me that the 32 Venturi where better suited to a larger engine they suggested running 30's. I would have to see if I could locate some replacement Venturi/ Chokes to see if this was the fault.

** Photo of Dellorto DRLA 40 Venturi/ Choke provided by courtesy of www.Dellorto.com

Upgrading replacement heads with Heavy Duty Valve Springs

11th Sep 2011.

It had been some time since my problems with my valve springs as I had found it quite difficult to locate some good second hand 1600 heads. Amazingly I found these eventually on hht://www.volkszone.co.uk web site and they where only a few miles away from me the whole time. I was lucky that the heads that I found had come from an engine that had only done 1500 miles or less so the heads had effectively already been run in.

I had managed to find some Heavy duty springs for same on eBay and new that they would have to be fitted to the new heads. This was as I had found to my cost that the standard springs would not take the compression from the ham and high lift rockers. I had also decided that rather than find chromoly push rods at this time I would use a set of bolt together 1:2 rockers I had purchased already.

The first thing I did with the heads was to remove the springs and valves and clean the ports on the heads. This in simple terms means smoothing the inlets to the ports with sand paper or an electric tool.

Fitting the Heavy duty Springs turned out to be a challenge my converted spring removal tool bent under the strain. I knew I would have to buy the bigger valve tool that I had tried to buy the last time from Cool Air before Bug Jam but decided this time to buy it from VW Heritage it arrived a day later.

The tool came in two package a package containing a split pin and the other containing the tool in separate bits. Amazingly there was no instructions for assembly but fortunately I had seen a diagram that I loaded up onto my site before showing it put together. The tool is a fantastic piece of kit but you need to learn how to use it. Firstly there are small pieces of tubing welded to the base these have to be aligned on the valve head . You cannot simply place the head on the tool and do all the valves without moving the head. Secondly when you press down on the arm after locating the tool head on the valve as in the picture the spring gives a little before it hits this block on the base. You need to press the arm quite hard after this to break the seal between the collet's and the retainers, they will usually let go with a thud and the spring will compress allowing the collet's to be picked out of the retainers with a bradel. Once the collet's are removed the arm can be released to allow the spring to be removed. The head then needs to be adjusted before this procedure can be repeated. The new collet's and retains are also heavy duty and it is easy to tell the difference. I found it a fiddle to get the Heavy Duty Valve springs on the tool and head. The main reason for this was the springs seem to be longer as well as thicker. I found that balancing the spring and retainer on the head and pulling down the tool head so it touched i could then push the spring and retainer into the tool head. I also found it difficult to get the collet's in place i found that insert in one then releasing the arm centralized the retainer and made it easier to fit the second collet in. The bradel was extremely useful to move these small collet's about as it had a sharp point.


Once I had fitted the Heavy Duty Springs I fitted the heads to my engine block. The heads push onto the barrels and are bolted up to 35 lbs/ft or 3.2 mKgs depending on your torque ratchet. The Heavy Duty Valves are easily identified as the retainers are a different shape. Once I had the heads torqued up I realized I had forgotten to install the air deflectors under the barrels , these are very important and slot under the barrels. They cannot be fitted with the heads on so I had to remove the heads and refit them a good lesson learned her check they are fitted first. I then fitted my 1:2 bolt up rocker arms you can see they are very similar to the Scat Pro Rockers but do not have quite so much lift. I torqued these up to 18 lbs/ft ( torque settings) I had broken a stud in the past and new these must not be over tightened. I fitted the tine ware over the heads and refitted the fan housing and the Alternator. these are fairly simple jobs apart form ensuring your fan is running freely there is not much more to it than bolting the tin ware together and using the alternator strap to tighten up the alternator. I moved my strap bolt round to the side so it did not foul the linkage kit . I fitted the carburetors and linkage kit with new gaskets (most important). I then left the engine over night so that it could cool enough for the valves to be adjusted. I used my own procedure to adjust the valves.

I just had the electrics to reconnect and decided that it was in need of a little restorations. I had used some spiral wrap before and decided that I would use this to protect the loom . I would have to purchase this and would refit the electrics next time.