Progress report

[RobD]

The planned work on the Fulvia has been moving forward at a glacial pace and I've had very little time available to get on top of the project. Any hopes of entering it in some early season hillclimbs went out of the window due to pressure of work and projects around the house. However, things are starting to look up. After much deliberation I plumped for a mild steel GP 4 exhaust from Omicron, eschewing the various stainless systems on offer from other sources. I'm very pleased with the Omicron system, it seems to be a well thought out piece of kit and came with lots of free advice, always welcome... I've sent it away to be ceramic coated inside and out, this will help keep down unwanted heat sink in the engine bay and of course it won't rust.



To go compliment the exhaust I picked up a brand new pair of DHLA 40s on eBay. They were too cheap to turn down and from experience gained building race bikes over the past few years I reckon you can't beat a brand new set of carbs. It takes such a lot of guesswork out of the set-up process. I enjoy tuning carbs and am really looking forward to installing these on the car. As soon as the correct manifold arrives in a few weeks I'll get to work tickling it up to match the Dellorto throats



I've always liked the look of those unfeasibly large Le Mans style filler caps fitted to some of the works Fulvias and last week decided to take the plunge and fit one. They look a bit brutal but therein lies the appeal. Of course they look all wrong with the filler flap in place and so I bit the bullet and had it welded over. That's it, no going back now, the Rubicon has been crossed!

[stanley sweet]

Good stuff Rob. You're going down a route I would probably take if I had any technical skills. Bet you can't wait to get the carbs and exhaust fitted. Like the filler and the flawless welding/repainting of the petrol flap. Look forward to more progress.

[RobD]

Hi Stanley,
I certainly wouldn't be over-egging my technical skills...
The DHLA 40Ns I've bought are very interesting. These are much maligned and viewed as inferior to the earlier carbs. I struggled to get any objective information about these carbs until I came across this written by an anonymous carb guru on the net. This is completely at odds with the numerous 'experts' who pop up on forums, most of whom have never tuned a carb in their life, they've just heard about someone who once knew someone who had! I'd struggled to understand these later carbs until I read this;


"Type 3 DHLA40F-G-H-N-R-S models.  These are called 'emission carbs' but are completely different to the DCOE type emission carbs.  Few people understand them and often try to tune them like the early models. These carbs differ from the early types 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 jet has 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 secret...

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 behavior 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 because 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.
Often people install the DHLA40 idle holders with the air holes into these carbs, add the 1-6-5-7 style tubes and wonder why they've got a massive lean spot off idle. It's simply because 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 in certain applications but dont' really do anything these late types won't do on all but the most highly tuned engines...I have run em all! These later carbs will give the maximum power available on any engine if you take time to tune them right. Be aware they are a bit more suited to standard motors , motors with mild cams or standard cams and they operate best if you are using 30-33 chokes. They hate full race engines, mad cams and mad chokes . They they are designed mainly for hot production engines with a clear pulse strength to suit the retarded venturi and tubes - great where good manners in town driving is still important, they also give superior economy to the early types.

So the DCOE is the same as the DHLA40, but the DHLA40E and F-G-H-N-L-R-S are all evolutions of a principle and provided the application is matched to the carbs best qualities you have the ability to cater for everyone's tastes and requirements using Dellorto..."

[stanley sweet]

Meant to ask - why will the manifold need 'tickling up' to match the Dellortos? Are they slightly the wrong type or you just want to get it spot on?

[RobD]

Hi Stanley,
 The manifold is coming from Omicron and I would imagine it will be sand cast from what is known as loose patterns [I could be wrong and it might be investment cast, but I would doubt it] Sandcasting components in small batches can often introduce small variances between individual components, this is perfectly acceptable from a QC issue in this application.

On something like a manifold the port apertures will be created by inserting cores into the pattern, these effectively fill out the void and cut down on material waste and post-production machining operations. The positioning of these cores can vary slightly between castings and could potentially introduce a lip or a step for the gas as it flows out of the carb venturi. before fitting a set of carbs it's good practice to check the alignment of the chokes with the inlet ports on the manifold and remove [ie tickle ]any obvious impediments to the progress of the gas.
I'll also be checking how the manifold ports  line up with the ports in the head.
Investment casting would be a more accurate way of casting a manifold but the cost of tooling be prohibitive.

[lancialulu]

Be careful if you decide to gas flow the head as you can get into the waterways and head bolts esp on no.4. A bit of a tickle at the port edge though should be fine. Its the junction between the manifold and head that is important as well as the juntion with the carbs....

Also dellorto tops can foul the bonnet.....as higher than solexes.

[DavidLaver]

On the topic of getting the bonnet closed:

http://www.lancia.myzen.co.uk/forum/index.php?topic=5639.0

[stanley sweet]

Thanks Rob, I understand now. Back in my motor club in the UK was an ex-Rolls Royce engineer who used to do a lot of work on competition engines and inlet manifolds. I'd always imagined they'd be polished super smooth to aid airflow. In fact he said the finish was relatively rough to cause the air to swirl.

[RobD]

Bit of a black art that Stanley, and you're into the realms of boundary layers and laminar flow!  The theory is , if you can upset the layer of air next to the surface of object the air is flowing over, the main bulk of air will flow faster around the object. Think dimples on golf balls ...

I won't be gas flowing the head Tim, experts tell me Fulvia heads are pretty good in this respect. My main priorities will be optimising the ignition and valve timing in conjunction with the carbs and exhaust. They'll be enough mischief in that little lot without delving into the head.

[Dilambdaman]

Lifted from the 'CUC 20H Fanalone thread:

"Jonathan has stripped and rebuilt the 48 Dellortos using comprehensive overhaul kits, checked the pump filter, overhauled the Filter King fitting new gaskets and spring, fitted a new set of points and she's running better than ever.  Smiley Another case of not knowing which was at fault or maybe it was a mix of all.

He also machine tapered the two faces of the inlet manifold which has lowered the carbs, had the radiator re-cored reducing the height by 20mm and lowered the height of the water manifold and the temperature sender. All of  which has resulted in the bonnet shutting level with the wing tops without fouling the carbs and radiator.  "

Robin.

[stanley sweet]

All interesting stuff. So if you dimple the entire bodywork of your Fulvia with a hammer you get an extra few mph out of it!

[lancialulu]

I won't be gas flowing the head Tim, experts tell me Fulvia heads are pretty good in this respect. My main priorities will be optimising the ignition and valve timing in conjunction with the carbs and exhaust. They'll be enough mischief in that little lot without delving into the head.

Getting a bigger exhaust valve will help match your Gp4 manifold and get a real gain. You cannot go up by more than a couple of mm but the surface area is a square of that....

[DavidLaver]

Anyone got a favourite YouTube link for an inspirational sound track?

[DavidLaver]

The engine sound is quite low but you might forgive that for other aspects:

https://www.youtube.com/watch?v=hDXRnEuQgbo

[RobD]

Great clip!

This is the soundtrack which convinced/inspired me to start looking at the Fulvia's exhaust and induction!

https://www.youtube.com/watch?v=cGiZR23VyhQ