Dellortro/Weber Tuning

[ellasOLE]

Hey all, does anyone know a great place in Sydney that does side-draft tuning and knows how to tune Dellorto DHLA 40G's?

These are the pair of 40 G's I have picked up. Plan is to put them on my 1.6L and 276 cam. Anyone who has done this conversion what was your jet,air,emulsion setup?

Any help would be greatly appreciated.

[sports racer]

Give Matt at Camden GTI a call - 02 4627 3072.

He's the only person I can think of that might be able to point you in the right direction other than a Fiat/Alfa mechanic. Some Fiats and Alfas came standard with twins.

You'll need to find someone with a dyno to properly tune the Dellortos.

Cheers

Paul

[Browneye]

Hey mate.

I'm running twin dellorto DHLA40H on my 1600 crossflow and they're function is relatively simple and don't necessarily need to be professionally tuned.

Read the following:

Type 3 DHLA40F-G-H-N-R-S models. These are called emission completely different to the DCOE science, but noone really understands them and tries always to tune them like the early models. These differ because they have more progression holes and use the*idle jet*to feed most of the cruise phase and low rpm/low TP area of the engine AT ALL TIMES when the main jet isn’t in operation completely automatically no jetting needed. The*idle jethas a very large fixed 2.2mm air feed, you cannot tune this phase of the carburetor for length like the others, but here lays the secrets….

The*idle jet*doesn’t feed from the*float*bowl, it feeds directly from the main jet stack, what happens after this is what gives these Dell’Ortos the sweetest road behaviour (what 25years of research came up with and not just for emissions) and dead easy tuning, you see when the main jet starts to emulsify fuel in the tube, the*idle jet*is feeding from it, so the gassy airy fuel shuts down the*idle jet*and sucks backwards yes BACKWARDS through the idle!! using every drip of fuel efficiently without ANY waste in circuit cross over where one is going after the other…this happens the moment the main jet fires, so there is NO need at all to tune the length of the progression and idle phase. This is pure magic they are automatically calibrated, you simply keep the*idle jet*above 59 up to 62 and not make the mistake of fitting numbers suited to the early DHLA or DCOE - with this simple technique you can tune anything from a 1300 to a 2000cc without really doing anything. The emulsion tubes in these carbs are always 8-10-11 and have to stay that way - which are really rich and have a hole straight down with loads of air holes, these atomise the fuel to an massive degree, also they have to be used cause the*idle jet*will not run correctly using the DHLA40-E type tubes (1-6-7-5) as the*idle jet*needs these airy tubes to function and cut out as designed…Usually people ram the DHLA40 idle holders with air holes in these carbs add the 1-6-5-7 style tubes and wonder why its a massive lean spot off idle, cause they missed the point completely!…These carbs use a .3 vent which has a very small*signal*tube*to the main jet stack, this is because the holey tubes are basically ready to go from about 1250rpm (on my car using an 8tube 1 vent it was on the mains at 1250rpm!) so the holey tubes need holding back with a signal killing venturi…These carbs are wicked if you want bolt on power, they tune themselves!

The early types are better in respect of punch and tuneability on odd applications but dont’ really do anything these late types won’t on all but the best engines…I have run em all! These carbs will give the maximum power available on any engine if you take time to tune them right, but they are a bit more suited to standard motors over 1500cc, motors with mild cams or standard cams and they operate best if you are using 30-33 chokes, they hate race engines, mad cams and mad chokes cause they they are designed mainly for hot production engines with a clear pulse strength to suit the retarded venturi and tubes - great where silk town driving and alike is paramount and you do commuting or just sunday driving, they also give superior economy to the early types.

My emissions carbs came off a 2.0l and I simple reduced the main jet size from 150 to 140 and backed of the power jet adjustment some. A good synchroniser is a must and good idle mixture is very useful.

If yours still have standard jetting you could use the same logic. Best starting point will be to see if the engine runs at all with these carbs.

Just a word of warning, these emissions carbs aren't designed for a cammed engine, and reliable cold starts are sacrificed. My 280 cam can be a menace to start on a cold morning.

P.S. They look and sound fantastic (see my thread for inspiration)

Good luck,
Jordan

[MarcusAurelius]

Amen! Browneye to the rescue as usual these days

[sports racer]

^^^^^^
What he said.

Some seriously good info there and now I'm on the lookout for some DHLA's as well.

[Browneye]

Thanks for the praise chaps but the knowledge isn't all mine. I can just attest that the theory works

[dubstar]

This is the website that I used to calculate the jets for my engine. Can't attest to the accuracy yet....

Slection and tuning of Dellorto DHLA carburettors

[Browneye]

This is the website that I used to calculate the jets for my engine. Can't attest to the accuracy yet....

Slection and tuning of Dellorto DHLA carburettors

This website is awesome for the DHLA40 (no suffix) and DCOE tuning, but the jetting theories cannot be transferred to the emissions carbs. Just be aware that an emissions carb set up using this jetting guide will run horrendously (I've tried and have videos to prove it)

[dubstar]

Interesting, you learn something everyday. Luckily the carbs I got are not emissions carbs (they are the 5 hole DHLA45s)

[ellasOLE]

The emission carbs also have 5 progression holes. The non emission ones have 3. Don't know if the 45's have the same internal workings but 5 holes is the long progression.

Also I've been talking with someone overseas who knows these carbs really well he told me the emission carbs work better than the earlier versions if you set them up properly. He runs a set of F's on a 300 degree cammed bmw m10 engine. About your cold start issues have you tried richening the starter jet? Also using the choke or not? What are your pump jet sizes?