Dellorto Tuning

[KENut]

Hey,

 

So I have twin DHLA 40's on my 4K, and I'm doing the baseline tuning to get it running reasonably well before dyno tuning.

 

Its currently running lean.

 

My question is should I;

 

1. Go to a larger main jet, then larger air if it still needs more fuel?

2. Go to a larger air jet, then larger main if it still needs more fuel?

3. Larger one of each by a certain increment?

 

Thanks, any tips appreciated

[RainWarriorDregs]

how are you determining that its running lean?

[ae95- wagon kid]

mate if you want it running perfectly take it to someone who knows what they are doing and get a really good tune it will cost more but if you supply the bits they need it will be cheap

[KENut]

Alec: 1. Its running hot and a bit rough

2. Spark plug discolouration

 

Wagon kid: Yeah I'm getting it dyno tuned soon, but I enjoy tuning myself and it will save some time. I have a fair idea what I'm doing.

Edited November 26, 2010 by KENut

[RainWarriorDregs]

I'm with you KEnut, its always more fun giving it a crack yourself and yhou learn on the way aswell.

 

My mate with dells on his gemmi said larger main then air if it needs it. Its not solid professional advice but mayeb a lead to work on.

 

good luck bro

[KENut]

Thanks mate, yep thats where I was going to start (mains then air). Cheers

 

Any other advice welcome too :)

[kangaroosa]

Bookshop

 

I have a copy of this. Its a good read and comes in handy if you want to get some knowledge on the concept of tuning Weber and Dellorto carbs. It gives suggested jetting specs for different capacity engines (good enough to get you driving safely to the dyno). It explains what parts of the carby come into operation at certain rev ranges. I highly suggest buying this book if you plan to tune your own car as it will save you money replacing main jets when you may need to be changing air correction jets or emulsion tubes etc.

Edited November 26, 2010 by kangaroosa

[Redwarf]

You can root around with it as much as you like, but they'll never be better than "pretty good".

 

Get thee to a Dyno, have them sorted by someone who knows their way around a carbie (rarer than you think...) and you'll never have to touch them again. And you'll never want to as you'll be too busy driving around looking for tunnels to drive through to hear the induction noise. :D

[philbey]

I'm assuming you've done your balancing as best you can? Some dellorto's you can actually balance the individual throats, later DHLA's (G's and on I think) don't have the balance screws, you can only balance via the linkage.

 

Buy the book kangaroosa suggested and have a fiddle. I think the biggest problem you'll have is getting hold of jets and emulsion tubes, I rang around every carby joint in adelaide and none stocked this gear. I had intended to get the correct sized based on the theory and get a couple either side of that to play with, but no luck. Gem Parts (Ebay) stocks some but they're not cheap.

 

In the end, I found out that my local dyno tuner is an Alfa nut and knows Dell's backwards. I had it tuned, went from 45kw to 68.5 kw and nearly 2 years later it's still running strong. I've not touched anything.

 

As Red said, you'll just spend all your time listening to your induction noise (except it sounds like a tractor on idle)

[KENut]

Its quite difficult to find decent tuning info on the web, so that book would be very useful kangaroosa! Will see if I can find it locally.

 

Redwarf: Poor little 4K has had lots more revs since I put them on :P . Tunnels are awesome

 

Philbey: Yes they're balanced, they are G's so yep only the linkage.

I've had the same problem sourcing jets, apparently the company that made them went bust. Might get some from the uk, or hopefuuly find someone with a stash local!

 

But anyway, all I want to do is fatten the tune up, and improve the progression from off throttle. Then I am going on the dyno!

 

Will find the current specs and put them up if anyones interested?

[KENut]

Minimum & maximum recommended sizes for 4K (& 5K in some cases)

From my research

 

Choke:28, 32

Main:120, 200

Air:170, 200

Emul:.1,.6

Idle:40,58

Pump:33, 40

 

Generally the recommended worked 4K starting point is around: 120 main, 180 air, 35 pump, 50 idle

 

And interestingly TRD spec:

Main:160-200

Air:180-220

Emul:7772.2

Idle:50

Pump:33

 

 

 

My current spec

 

DHLA G

32 choke

120 main

170 air

7772.1 emuls

55 idle

35 pump

Edited November 26, 2010 by KENut

[RainWarriorDregs]

i was having a look at that book, is it only for sidedraught carbs? i'd love to find something like that for downdraught webers to learn a thing or two, they still confuse me.