#DELLORTO 001

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http://www.bitsofitaly.com/dellorto-dhla-parts/

The DHLA & DRLA carburettors are widely believed to be the most sophisticated carburettors of their type, prompting David Vizzard to say in Auto Performance magazine, “Dellortos produce truly excellent results...On engines where atomisation is a premium requirement, Dellortos are superior to everything”.

The last carburettors Dellorto produced were the unique 'tri-jet' DHLA45s for Lotus, which as well as an idle and main circuit, has a power jet circuit for extra enrichment at high revs. This system was also fitted to the Lotus Esprit Turbo carburettors, which can hold up to 30-PSI boost pressure. Eurocarb ltd stock every single part for DHLA, DRLA & DHLB carburettors, as well as complete new and some reconditioned units

https://www.dellorto.co.uk/?s=Dhla+45c&post_type=product

https://www.dellorto.it/en/company/history/

Edited October 29, 2023 by anthonym

#Dellorto 002 FLOAT LEVEL

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SUMMARY

02 = 8.5g       15.5 - 16.0 mm

Intended to achieve

27mm from top to fuel level.

Fuel pressure is important. The Dellortos like 1.5 to 2.5 psi at the carb inlet. Higher fuel pressure can over-power the inlet shut-off valve, and result in an overall rich condition. If the inlet pressure is too high, then install an inline adjustable fuel pressure regulator, and set it for 2.0 psi.

======================================

Switch off. Promptly remove the top cover. Using the depth gauge feature of a vernier or dial caliper, measure down from the top of the jet pedestal in the float bowl, near the middle between the two Idle Jet assemblies, down to the fuel surface. The correct level is 27mm / 1.063”. Adjust the Float Height and repeat the procedure as required to achieve that level in both carbs. If each available weight float is set to it's specific correct height, then all float weights will result in the same standard 27mm fuel level in the float bowl. Setting the Float Height is an easy expedient, but correctly setting the fuel level is the real goa

The Dellorto part number for the floats is 7298-99-_ _ with two final digits for each weight:

01 = 10 gr, 16.5 - 17.0 mm Float Height.

02 = 8.5 gr, 14.5 - 15.0 mm Float Height.

03 = 7.0 gr, 16.5 - 17.0 mm Float Height.

(01 = 10 gr, 14.5 - 15.0 mm, Non-standard, Lotus sometimes used a higher fuel level to create an overall richer mixture)

BUT 

https://sideways-technologies.co.uk/forums/index.php?/topic/1048-setting-dhla-dellorto-dellorto-float-fuel-level/

Either the weight or the float part number should be engraved on the float.  3 types the 7g,  8.5g  and 10.0g floats.

The basic part number for the floats is 7298-_ _   with two final digits for each specific weight:

01 = 10g        16.5 - 17.0 mm (float height start setting)

02 = 8.5g       15.5 - 16.0 mm

03 = 7.0g       14.5 - 15.0 mm

AND FROM HERE

https://www.dellortoshop.com/contents/en-us/p28_7298-Float-Assembly-for-Dellorto-DHLA-carburetor.html

7298
Float Assembly for a Dellorto DHLA carburetor.

Always replace an existing float with the same version.

Available in the following versions:

• 7298.1 8.5 grams, replaces the earlier versions of 9 and 10 grams and replaces the no-longer-produced 7298.2.
  In the mean time, Dellorto has ceased the production of this 7298.1 as well and, consequently, this is a European-made reproduction.
• 7298.3 (7 grams)

Please note that version 7298.2 is no longer produced. Please use 7298.1 as a replacement.

Edited October 29, 2023 by anthonym

#Dellorto 003 Mixture setting

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• Turn clockwise to lean the mixture, and anti-clockwise to
  richen the mixture. 
•  
• because
• lean mixtures cause higher running temperatures.
•  
• Spitting back through the back of the carburettor normally indicates that the mixture is too weak, or the timing is hopelessly retarded 
•  
•  
•  

http://www.jensenhealey.com/forums/view_topic.php?id=2246&forum_id=4

 

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Quote

Reply

Esprit2 Member      Joined:  05-01-2005 Location:  Minneapolis, Minnesota USA Posts:  571 Status:  Offline

Carbs require a little black art to tune them. They are not ECU controlled with sensors and feedback loops, so it's not a simple matter of working out some ideal settings, plugging them in, and it runs perfectly. All the generic formulas, as in the Speedpro book, will get you close, but plan on doing some tuning afterwards. Also, carbs don't have the flexibility of an ECU controlled fuel injection systems, so you can tune for peak power, or best driveabililty, or best economy, but not for all at once. You need to choose what you want, and "both/ all" isn't a choice.   The best way to approach jetting of a custom installation is to take it to a shop with a rolling road dynamometer, an exhaust gas analyzer, and (hopefully) a comprehensive supply of Dellorto jets and parts. I'm fortunate to have one near me.   It's also important to keep the three-Cs in balance... Carbs, Compression & Cams. If a big set of carbs are just bolted onto a mostly stock sedan engine, then the resulting gain will probably be be less than hoped for with the stock compression and cams. For best results, the 3-C's need to be optimized together. The B30's 10:1 compression is higher than I would have guessed, but it's not "hi-performance" high. I know nothing about the cam, but expect that it's fairly mild.   I'm not familiar with Volvo 164/ B30, but I'm thinking a pair of 45mm DHLAs is a lot of carb for the existing compression & cams in a 496cc/ cylinder engine. Then add in the 36mm chokes, and I think the engine is a little over-carbureted. Now, maybe the 164 is a hotrod Volvo, and loves the carbs; but without knowing more, I'm betting that's not the case.   I suspect the Lotus 907 (493cc/ cylinder Vs B30's 496cc/cyl) is a bit more of a hotrod than the B30, and the Jensen-Healey version of that engine uses 40mm DHLAs with 35mm chokes. The Lotus version of the same basic 907 engine uses 45mm DHLAs with 36mm chokes, but Lotus also targets a more boy-racer clientelle. Flog the engine and it goes, but it's not meant for casual driving. Many J-H owners criticise the Lotus-spec 907 for having too little torque at low rpm, and not being easy to drive in commuter traffic. Big carbs just aggravate that condition.   So what are your goals for the Volvo B30 engine?   Searching the internet, I find: 2980 cc 6-cylinder (496 cc/cyl) 88.9 mm x 80.0 mm bore/stroke 145 bhp (SAE) at 5500 rpm 163 lbs-ft at 3000 rpm.   Using some standard formulas and assumptions, I get the first two columns: ............................... Generic ......... Generic .......... Stock Engine .................... Volvo B30 ...... Volvo B30 ....... J-H 907 ........ Yours Displacement (cc/cyl) 496 ............... 496 ................ 493 .............. 496 Power Peak RPM ...... 5500 .............. 5500 .............. 6500 ............ 5500 Tuned for: ............... Power ............ Flexibility ........ J-H Stock Carb Type ............... DHLA 40 / 45 .. DHLA 40 ......... DHLA 40 ...... DHLA 45 Choke ..................... 36 mm ........... 34 mm ........... 35 mm ......... 36 mm Venturi Reduction %.. 0.90 / 0.80 ..... 0.85 ............... 0.875 ........... 0.80   Main Jet ................... 145 ................ 140 ................ 130 .............. 150 Main Air Corrector .... 180 ................ 180 ................ 160 .............. 160 Ratio, Air Corr/ Jet ... 1.241 .............. 1.286 ............. 1.231 ........... 1.067 ................................................................................................... 180 SpeedPro Ratio, Air Corr/ Jet ....................................................................... 1.200   Main Emulsion Tube.. 7772-6 or -5 for both ................ 7772-5 ......... 7772.7 .................................................................................................... 7772.4 SpeedPro   Idle Jet ..................... 50 ................... 50 ................. 50 ................ 60 .................................................................... I prefer 55 ................ 50-55 SpeedPro Idle Air Corrector ...... 7850-2 ............ 7850-2 ........... 7850-1 .......... 7850.9 ................................................................... I prefer 7850-7 .......... 7850.6 SpeedPro ................................. 2nd richest ...... 2nd richest ... "normal" ......... 3rd leanest   Pump Jet .................. 40 ................... 40 ................. 45 ................. 40 Auxiliary Venturis ...... 7848.2 ............ 7848.2 ........... 7848.1 ........... 8011.1 Aux Vent sized for ... <550 cc/ cyl .... <550 cc/ cyl ... >550 cc/ cyl ... >550 cc/ cyl Aux Venturi should be ............................................... Lotus uses ..... 8011.2 SpeedPro ........................................................................ large Aux Venturi.... a size too big Pump Delivery in 20 Strokes ...................................... 8.0cc Pump Lever Clearance (mm) ...................................... 0.1 +/- 0.05 Fuel Delivery Pressure (psi) ....................................... 1.5-2.5 at carb inlet   Idle Air Corrector Jets (aka, Idle Jet Holders) are not numbered sequentially, but totally randomly. Don't get caught making any assumptions about which one is the next size richer or leaner. Go by the following chart:   7850.5 .. Leaner, going down the list gets richer. 7850.10 7850.9 .. In your Volvo B30, pretty lean. 7850.4 7850.1 .. Normal 7850.3 .. Normal 7850.6 .. Normal, 6 & .7 are very similar, almost interchangeable 7850.7 7850.2 7850.8 .. Richest   That's a lot of writing to not come up with a specific recommendation, but I'll fall back on the earlier statement that you can't calculate a correct setting for carbs, and then have it work first time when you plug it in. But having looked at all the above...   Fuel pressure is important. The Dellortos like 1.5 to 2.5 psi at the carb inlet. Higher fuel pressure can over-power the inlet shut-off valve, and result in an overall rich condition. If the inlet pressure is too high, then install an inline adjustable fuel pressure regulator, and set it for 2.0 psi.   Next, the fuel level in the float bowl is critical to correct mixture control. There are three or four Float Weights available, and each has a different required Float Height setting. If you use the wrong height for the weight that's installed, then the fuel level will be wrong, and everything goes to heck from there.   The Dellorto part number for the floats is 7298-99-_ _ with two final digits for each weight:   01 = 10 gr, 16.5 - 17.0 mm Float Height. 02 = 8.5 gr, 14.5 - 15.0 mm Float Height. 03 = 7.0 gr, 16.5 - 17.0 mm Float Height. (01 = 10 gr, 14.5 - 15.0 mm, Non-standard, Lotus sometimes used a higher fuel level to create an overall richer mixture)   Remove the carb's top cover. Use a small scoup, or an eye dropper/ turkey baster to remove a little fuel to create a low condition. Re-install the top cover. Switch on and run the electric fuel pump until it's tone changes, indicating the float bowl is full. If the pump is mechanical, then remove the coil wire, and crank the engine over (without starting it) long enough to ensure that the float bowl is full and the float has closed the inlet valve.   Switch off. Promptly remove the top cover. Using the depth gauge feature of a vernier or dial caliper, measure down from the top of the jet pedestal in the float bowl, near the middle between the two Idle Jet assemblies, down to the fuel surface. The correct level is 27mm / 1.063”. Adjust the Float Height and repeat the procedure as required to achieve that level in both carbs. If each available weight float is set to it's specific correct height, then all float weights will result in the same standard 27mm fuel level in the float bowl. Setting the Float Height is an easy expedient, but correctly setting the fuel level is the real goal.   Don't try to do any tuning until the fuel pressure and Float Height (fuel level) are correct !   IMHO, the 45mm DHLAs and 36mm chokes are on the large side for a Volvo 164/ B30 (while admitting that I know nothing about them). But given that is what you have, and that changing the sizes will be expensive, lets just roll with it for now.   The Main Jet and the Main Idle Air Corrector are both too rich. If you stay with the rich 150 Main Jet, then I think the Main Air Corrector number you got reading the SpeedPro book is going in the right direction, but maybe even 185-190. But if you reduce the Main Jet a size or two, to a more reasonable 145 or 140, then a 180 Air Corrector is about right.   I don't know what to say about the Main Emulsion Tube... that's more black magic than I can stir in my kettle.   The Idle Jet also seems too rich to me. I'd expect to go 55, 58 max, but 60 just seems like too much. And the Idle Air Corrector is the third leanest one available. The number you got from SpeedPro, 7850.6, is about right, but my favorite is 7850.7. The .6 and .7 are very close, and almost interchangeable, but the .7 is a wee bit richer. If the engine doesn't have to pass an emissions test, then a little richer is good.   The transition point between the Idle and Main circuits occurs at about 3200 rpm. The Idle Jet must be just large enough to have the flow capacity to feed the engine up to 3200 rpm, but be no larger than required. Then the Idle Air Corrector is sized to add the right amount of air for the best A/F ratio. The best way to set the Idle Jet and Idle Air Corrector sizes is to...   1) Give the ignition a tune-up. 2) Accurately balance the carbs (that's critical). 3) Set the Idle Mixture screws for peak manifold vacuum. 4) Set the Idle Speed as slow as possible consistent with smooth running. Then...   5) Open the throttle slowly enough that the accelerator pump isn't much of a factor. If the engine hesitates off-idle, then go a step or two richer on the Idle Air Corrector. If the engine does not hesitate, then go a step or two leaner until it does 'just' hesitate, then go back one step richer until the hesitation just disappears. The result will be fine sitting in the driveway, but in real world driving, you may find that the hesitation becomes noticable. If so, go a step richer with the air corrector until the hesitation just goes away.   6) Next, set the Idle Speed to normal (~900 rpm) and go for a drive. Short-shift into a middle gear, then accelerate at full throttle to well past 3200 rpm. If the engine stumbles at around 3200 rpm, then the Idle Jet is too lean, and the circuit is running out of capacity before the Main Circuit kicks in. Go a step or two larger/ richer with the Idle Jet until the stumble just goes away. If the engine does not stumble, then go a step or two leaner until a stumble just develops, then go back richer one step until it just disappears. Do not go richer than is required to eliminate the stumble.   The current Pump Jet size is close to right, but could go a step larger to 45 or so. I don't think it's the root cause of any running problems. The pump's stroke should be adjusted to deliver 8cc of fuel in 20 strokes. That sets the total volume of fuel that can be delivered. The linkage is spring loaded, so fully opening the throttle spring-pressurizes that volume of fuel, then the size of the Pump Jet determines how quickly that volume will be delivered. A fat stream that's gone in an instant, or a skinny stream that lasts a long time. If the pump linkage isn't correctly adjusted to deliver enough fuel, then changing the Pump Jet larger isn't going to cause more fuel to flow.   The only way to correctly adjust the linkage is to use two graduated cylinders (chemistry lab bits), one in each throat, then fully stroke the throttle 20 times. Measure the fuel dispensed, and adjust the linage accordingly until 8cc is achieved.   Koit wrote: “One other question, it seems these carbs don't have air bypass valves for balancing, so how should I balance them? ”The manometer vacuum ports appear to be present, but the Air Bleed Screws are covered with anti-tamper plugs. Those aluminum domes in the bosses. Pry out the anti-tamper plugs, and you'll probably find the Air Bleed Screws.   Failing that, an airflow meter, like a Synchrometer, will work. The problem with any instrument that is placed over the carb's inlet is that it disturbs the very airflow it's trying to measure. A manometer is best, but an airflow meter will work. A Uni-Syn is another type of airflow meter, but it's best used as wall art.   Koit wrote: “I haven't measured the exhaust yet with wideband lambda but It seems the mixture is a bit rich, the spark blugs where carbon fouled. So what do you guys think? ” I think both the Idle and Main circuits are currently too rich, and the carbon fouled plugs confirm that.   Good luck, Tim Enge

Joined:	05-01-2005
Location:	Minneapolis, Minnesota USA
Posts:	571
Status:

Edited October 29, 2023 by anthonym

#Dellorto 004 Service Manual

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http://www.motorcyclecarbs.com/Dellorto_DHLA_Service_Info_W168.cfm 

 

Service Manual Available

on the DHLA you can control the time the pump jets squirt for against the rate of flow by adjusting the spring tension on the actuating lever (ie a lot of fuel for a short time or less fuel over a longer time, the same total flow in each case)

the nut and locknut fitted on the pump operating rod

 whereas a high fuel level usually comes over the top and drains down both the throats.

Dellorto Carburetor DHLA Service Info

CARBURETOR SYNCHRONIZATION AND IDLE ADJUSTMENT

Proper carburettor synchronization and idle adjustment requires an exhaust gas CO meter, a rev-counter and a four-column mercury manometer.

Proceed as follows:

    * Disconnect the throttle control rod and lever (1).

    * Unscrew the idle speed screw (2) out of contact with lever extension (3).

    * Unscrew the screw (4) of the balance lever (5) until the throttles of both front and rear carburetors are fully closed. Check they are with light upward pressure on lever (1) While maintaining pressure on lever (1), tighten screw (4) until it contacts the tongue of lever (1), thus fully closing the throttles of both front and rear carburetors.

    * Tighten the screw (2) one more turn after it first contacts the extension (3) of lever (1).

    * Remove the anti-tamper seals from the mixture screw housing (6) and unscrew each screw five turns from the fully-closed position.

    * Check that the idle air bypass screws, to which anti-tamper paint has been applied, are completely closed- Remove the depression blanking plugs (

 

 and connect each barrel to the four-column mercury monometer using the screw-in adaptors.

    * Reconnect the Throttle operating rod to lever (1).

    * Start the engine and leave it running to attain normal operating temperature.

    * First ensure that any airlocks are removed from the mercury columns which will otherwise result in inaccurate readings.

    * Align the lower mercury column of the front carburettor with the lower one of the rear carburettor using balance screw (4).

    * Then, if necessary, adjust the levels of the other two cylinders to match those of the lowest pair using the bypass screws on these barrels With the No 1 cylinder blow-by pipe temporarily clamped shut, all readings should be brought to the same level. Unclamped for normal running, No 1 cylinder’s mercury level will always be lower than the other three cylinder levels.

    * Insert the CO tester probe and connect the rev counter.

    * Preferably only by using the special Dellorto screwdriver, adjust the running of each cylinder by turning the mixture screw (6) to get the most even running with the engine idle speed at the correct level and holding the exhaust CO level well below 4,5%. Remember that by unscrewing these screws you increase the CO level and vice versa. The mixture screw of barrel (1) will need to be opened more than the others due to the effect of the blow by hole on that cylinder- Remove the vacuum adaptor plugs and refit the blanking plugs in their place.

    * Fit new anti-tamper seals on the mixture screw housings (6).

If all the above-mentioned equipment is not available, it is still possible to obtain the correct idle setting by simply resetting the idle speed screw (2) at the balance adjusting screw (4).

DHLA 40-45-48

Applications:

ALFA ROMEO

1300- 1600 Giulia Super

1600 GT Coupe’ - 1750 Saloon

2000 Saloon - GT Coupe’ - Spider

LOTUS CARS

Europa Twin-cam - Elan -

Elan Plus - 2S

1. FEATURES

    * Twin-choke side draft body.

    * Barrel sizes, 40 - 45 - 48 mm.

    * Interchangeable chokes available in sizes ranging from 25mm. to 43 mm. inclusive.

    * Butterfly throttle valves.

    * Centrally-placed constant-level float chamber with double float.

    * Main circuit using centrally-placed main jets and emulsion tubes.

    * Idling circuit with centrally-placed idle jets drawing fuel directly from the float chamber.

    * Independent starting circuit with single starter jet and valve and separate channels to each barrel.

    * Diaphragm accelerator pump, mechanically-operated, with single inlet valve, two delivery channels and individual valves and pump jets.

2. OPERATION

a - Starting

Fuel at the union (2) passes through the filter (1) and reaches the seat (14) where the needle (15), attached to the float (17), controls the fuel flow into the float chamber thereby maintaining a constant level. The float chamber is vented to the atmosphere through the vent (4) in the chamber. On opening the choke valve (7), fuel metered through the starter jet (12) passes into the emulsion tube (11) where it is mixed with air from the channel (16) and then enters the passage (6) further mixing with air from the vent (5) and reaches the valve chamber. From here, it is distributed via the two ducts (9) which lead into the main barrels (10) downstream of the throttles. On closing the choke valve, communication between the main barrels and the starting circuit is broken as well as communication between the two barrels due to the sealing action of the split bushing.

b - Idling

Fuel from the float chamber is metered through the idle jets (20) and mixes with air from the well (3) through the channels (19). Mixture through channels (21) reaches the idle mixture screws (22) and, when regulated by them, reaches the main barrels (10) downstream of the throttles (13).

c - Progression

On first opening the throttles (13), that is, when passing from idling to full throttle, mixture also reaches the two barrels (10) through the progression holes (23).

d - Acceleration

On opening the throttles (13), the lever (28) attached to the throttles spindle (27) by means of the rod (29) and spring (34) pushes the pump lever (32) which acts directly on the pump diaphragm (31) which is normally held out by the spring (30). The pump diaphragm then pumps fuel into the two main barrels (10) via two separate channels through the delivery valves (24) and the pump jets (26). On closing the throttle, the diaphragm returns to its Full position pushed by the spring (30), drawing fresh fuel from the float chamber through the inlet valve (25). The nuts (33) adjust the pump injection quantity.

e - Full throttle

At full throttle, fuel from the float chamber is metered through the main jets (37) entering the wells (36) and mixing with air metered through the air corrector jets (9). This mixture then passes through the channels (39) to reach the auxiliary Venturi (38) where it is further mixed with air drawn into the main intake and finally flows into the Venturi (40) to reach the barrels (10).

3. ADJUSTMENT

a - Idling

Always adjust the idle with the engine hot, screwing in the idle speed screw (a) to obtain a slightly higher idle speed than normal. Then adjust the mixture adjusting screws (b) until you find the most even running; remember that unscrewing them results in a richer mixture and vice versa. Then steadily unscrew the idle speed screw again until the normal idle speed is reached.

b - Accelerator pump

Adjust the accelerator pump injection quantity by fitting the carburettor to the special support with the proper gasket and connect the carburettor to a reservoir so that it is continuously supplied with fuel.

Put the two graduated measuring tubes, each having a capacity of 10 cc, under the drain pipes on the support in order to collect all the fuel pumped out. Open and close the throttle completely 20 times, with a few seconds’ break in between each time, and check that the amount of fuel collected in the tubes corresponds with the correct specification and is the same for both barrels. It not, adjust the pump delivery by resetting the nut and locknut fitted on the pump operating rod; remember that screwing the nuts up increases fuel delivery and vice versa. It there is any difference in volume between the two barrels, remove the pump jets and blow through them vigorously to correct this. Recheck until the correct setting is obtained and then ensure that the nut and locknut are retightened.

c - Float level

Check that the float has the actual weight which is marked on it, is undamaged and also tree to rotate on its pivot pin. Hold the carburettor cover vertically so that the float arm is in light contact with the needle and with the spring in the needle not compressed. In this position, check that both half-floats are at the correct distance from the float chamber cover measured to the top cover gasket fitted to it.

float    A    

7298.1

7298.2    14,5 ÷ 15

16,5 ÷ 17

4. MAINTENANCE

To keep the carburettor in good condition, especially after operating faults have occurred, proceed as follows. Dismantle the carburettor, washing the components in fuel and blowing dry. Special care is needed with the jets, emulsion tubes, needle valve seat, fuel tilter and all the drillings in the carburettor body. Check the condition of all the components before reassembling and replace them wherever necessary only with new parts. When reassembling the carburettor, renew all the gaskets and O -rings.

Dellorto DHLA carburetor and parts.

http://www.motorcyclecarbs.com/Dellorto_DHLA_Service_Info_W168.cfm s ove stranice je kopirano,malo ću se zabavit prijevodom,pa da prevedem na naš jezik,dosta je teh. pojmova,pa moram malo pogledat,mislim da je dosta korisno.

Edited October 29, 2023 by anthonym

#Dellorto 005 Accelerator pump

 

Screwing the nuts up INCREASES fuel delivery

 

I found Alan above's comment extremely useful, one carb needed no further adjustment, the other not much, and my carbs were far out - and I had no pump jet petrol at all, so the car always stalled on hard acceleratiuon "WOT".

Screwing the nuts up INCREASES fuel delivery

 

Me too, it's impossible

 

 

#Dellorto 006 Techtalk question from me and comments

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DELLORTO DHLA CARBURETTORS - DISCUSS / TUNE /FETTLE?

Dellorto DHLA Carburettors - discuss / tune /fettle?

I am busy tuning and fettling my twin Dellorto DHLA 45s doing things like Balancing with Carbtune Pro, fixing float levels and such like. My current exploration is how to fix my accelerator pumps which seem to be inoperative, one leaks (both barrels) and I suspect the 5mm gap at the end of the push rod is "missing", but that looks like I may have to remove the carbs from the car to fix and if removed to service the pump mechanisms (i.e. x 2). 

Purpose of my post here is to see if anyone else is interested in these sorts of things? Or even has experience of same. All first time for me. My carbs have been refurbished, but this was 9 years ago and only brought in to use relatively recently (a year maybe).

So ball bearings "stuck" are possible etc. My sources of reference are google, many web sites, youtube  and the book 3rd edition of SpeedPro 

"How to Build & Power tune Weber & Dellorto ..... DHLA Catburettors

https://www.amazon.com/dp/1901295648?tag=webercarburetorrebuildkits.com1-20&linkCode=osi&th=1&psc=1

". I can't find any version of the Dellorto Tech book

https://www.amazon.com/Dellorto-Tech-Superformance-Calibration-guide/dp/B0013I6YG2

 even in pdf anywhere. I also have contact with "my" carb refurbisher who seems to remember me. My previous owner/builder (r.i.p. 2018 age 90) assured me in about 2003 the jetting is perfect so I have no intention of changing any jets. Sounds like main jet "34" is ideal for my 1987 1700 BDR on standard 169bhp.

The Speedpro book is hard work because it combines both Weber and Dellorto in the same texts  - and avoids discussion of setting the length of the accelerator pump drive pole saying " do not touch".

So, anyone like to play this game? Sandpit now open.

(Do we have an index of all Dellorto DHLA chat on here

https://duckduckgo.com/?q=site%3Acaterhamlotus7.club+dellorto+dhla&ia=web

? Answer is no not really.)

The carb balancing has also greatly improved the overheating problem as they were very (very) un balanced.

#4 Wrightpayne

DHLAs - thats an unusual fitment - factory fit or later modification? 
 

#5 anthonym

That's an interesting question. As far as I know it was included in the self-build from a CKD Kit. (Completely Knocked Down). Our most excellent archivist recently found my car's Purchase order; I'll have a look. So, no sign of the engine which he told me he bought direct from Cosworth with some mods he wanted. (I am since told buying from Cosworth direct was not possible; maybe an engine builder who was trading as if Cosworth.. or whatever.) The Dellortos were on the car and he spoke as if they had always been there from the start. 

I found the CC Pro Forma invoice, but engine not included, though of great interest to me in my provenance search, sold as a "BDR" and even with the "HPC Course", but not VIN recorded as an HPC because (a) not factory built and (b) engine not supplied by CC.

The 1987 BDR basic spec, I see Weber 45s which explains why my Dellortos are 45s when these days I am told these are "too big". Reading the book above says the Dellortos have a slight edge over Webers in terms of tunability at that time, and my builder told me he spent years tweaking jets so presumably he enjoyed and chose this choice as it were.

Great question, thanks.

  BDR1700 price list 1987-1.pdf

The above file is displayed in full in the original thread - or click it

Edited October 29, 2023 by anthonym

#Dellorto 007 FLOATS

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8.5g These are 15mm top 25mm lower - and fuel top from lid top under gasket has to be 27mm

This information gleaned form a lot of not entirely consistent internet content

Edited October 29, 2023 by anthonym

#Dellorto 008 Throttle bodies?

 

#BDR 

My BDR Venturi is “ 38 “

Benefits of individual throttle bodies

https://youtu.be/uS3yHPfT9I8?si=SK-nN6xZhLd9WZLp

There are significant benifits to doing this correctly, using either Jenvey DCOE style TB or their Heritage range, for an original look, run this along side a 3D ignition under the control of an Emerald, yes it will add up but these are good real world upgrades, the ignition map in particular will make a huge improvement.

Discount is available on the ECU from Emerald,

You will need new fuel pump pressure reg, tank, injectors fuel rail and a few sensors etc to crank, TPS, water and air temp

Don't forget to factor in a mapping session too,

3D Ignition system

https://www.alfaholics.com/race-parts/105-series/engine-2/full-3-dimensional-ignition-map-for-twin-spark/

Basically what 3d means to your car and driving experience is as follows:

Far less popping/banging from the exhaust on the overrun, as there won't be any unburnt fuel in there as the spark will be in the right place at the right time at 0% throttle

Slightly better fuel economy due to the above

Potentially better throttle response as the ignition map will be taking into account the throttle position therefore allowing the engine to get the spark 'just right'

All of the above contributes to much smoother running engine.

If I were you, junk the alpha ECU and get a MegaJoltLiteJr or similar and use the same sensors if you can. That way you've got a nice easy solution that you can use your laptop to program to your hearts content.

My xflow has had a new lease of life since it was installed...

Will.

Carbs versus TBs

https://fixingengines.com/throttle-body-vs-carburettor-whats-the-difference/

 

A carburetor cannot measure the correct air-fuel ratio and struggles with changing fuel temperature and air pressure. In contrast, a throttle body with an electronically controlled fuel injection system can constantly alter the fuel delivery to the cylinders – better performance.

A carburetor cannot adjust the fuel ratio according to the engine conditions, resulting in poor fuel economy. On the other hand, a throttle body works with a well-controlled fuel injection system to deliver the precise amount of fuel, adjusting it according to various parameters – less fuel wastage.

A throttle body is better than a carburetor in the following aspects:

• Lower emissions
• Smoother idling
• A better cold-start and performance.
• Better driveability and fuel economy
• It is easier to tune, and the throttle response is better.
• Fuel injection systems are best for off-roading because they decrease vibrations and help to overcome steep grades.

You can buy a brand-new street performance carburetor with a price range from $300 to $800, whereas a new TBI fuel injection system will cost around $2,500 to $2,800. Ultimately, what is best for you depends on your type of car and the depth of your finances.

https://www.omnicalculator.com/physics/carburetor-cfm

DVA on Dellortos

http://www.s262612653.websitehome.co.uk/DVAndrews/dellorto.htm

My BDR Venturi is “ 38 “

38*1.25 =47.5

When you are sure that the carbs are drawing the same volume of air, visit each idle mixture screw, turn the screw counter clockwise (richening) in small increments (quarter of a turn), allowing a good 5 - 10 seconds for the engine to settle after each adjustment. Note whether engine speed increases or decreases, if it increases continue turning in that direction and checking for engine speed, then the moment that engine speed starts to fall, back off a quarter of a turn. If the engine speed goes well over 1000RPM, then trim it down using the idle speed screw, and re-adjust the idle mixture screw. If engine speed decreases then turn the mixture screw clockwise (weakening) in small increments, again if engine speed continues to rise, continue in that direction, then the moment it starts to fall, back off a quarter a turn. The mixture is correct when a quarter of a turn in either direction causes the engine speed to fall. If that barrel is spitting back then the mixture is too weak, so start turning in an anti-clockwise direction to richen. During this procedure, the idle speed may become unacceptably high, so re-adjust it and repeat the procedure for each carb barrel.

https://bmwmotorcycletech.info/dell.htm

A stoichiometric mixture ratio is one which ensures complete combustion of fuel with only the formation of water and carbon dioxide.

The stoichiometric mixture ratio depends on the kind of fuel used, so if the fuel is changed, this fuel-air ratio will also change (see SECTION 5.1)

Passage of fuel from the float chamber to the main barrel is brought about by the pressure difference existing between the float chamber and in the barrel itself; this fuel movement takes place because the float chamber is at atmospheric pressure while, as previously mentioned, the pressure is lower in the choke (figure 7).

Dellorto 009 The Instructions - last resort

I can't find the source of this to attribute it

and pdf version

Tuning Carbs.pdf