What Carburettor? - Race 1300 Engine

[RealWorld]

The time has come to plan the race car rebuild. My intention is to collect bits now, and have it ready to test by April. We'll see ;-/

 

Much of the work is refurbishment and replacement pretty much like for like. No problem there, just time and effort required.

 

The big decision area is the carbs, and air filters. Like many race 1300 Spits, the car was running twin Weber 45s, able to deliver the fuel/air flow required for 8000rpm plus. I'm now pretty sure that these carbs, in combination with the air filter sock pushed over the trumpets, are what caused the fire at Snetterton earlier this year. Excess fuel, a little backfire, saturated sock too close to the extractor - all added up to a messy fuel fire.

During the 30secs or so of burning, the rear carb was pretty much destroyed, melted chokes and all.

 

Now is the time to choose the replacement.

 

Easiest solution is to source 2 more 45s, jet and choke them the same, organise better air filtration and then go RR tuning. Probably cost circa £700 buying new as I have the linkage and manifolds.

 

But are there other/better/more interesting solutions? Bike carbs? Jag size SUs?

 

And if I go twin 45s - what's the best air filter compromise between flow and backfire/fire protection?

 

I'm on a budget here and getting the car racing is the priority rather than ultimate performance at greater cost - but I don't want to miss a trick and go like for like without consulting the wisdom here.

 

Thoughts?

 

R

[mattius]

My car spits flames out the carbs occasionally when cold, the itg megasausage thingy has never caught fire yet, infact the claim its fire resistant.

 

Are twin 45s not overkill for a 1300 though? i thought the choice was single 45 or twin 40?

[DaveNotSoSideways]

I'd avoid new webers they are absolute junk.

 

I'd be ebaying for some DHLA45E, D, M, C models. Buy best you can. Same price as some foul webers you can have a well layed out 45 dellorto rig and change.

 

Least flameproof carburettor setup is one in tip-top order. Carb's set on fire cause they are poorly setup, badly setup for fuel pressure or some other problem, same reason they ingest metal pieces from carbs, it's just a lack of awareness. If the carb has excess fuel sat in it at anytime it's not setup right. If the carb smells of fuel it's badly layed out, there should be no smell of fuel or any fuel leaking at all, even with a foam filter. I can work by my carbs with the engine running an there is no fuel stench.

 

The most likely way to enduce a fire is to run those socks as they will soak up fuel from the useless leaky venturi/trumpet setup on those Webers and doubly so if the angle of the carbs is too flat, they need 7deg of angle to stop fuel running down the throats out the trumpet. On a Dellorto you can use a flat flange trumpet and a gasket to prevent fuel from leaking out the base of the carb from the trumpet area. Webers are shit honestly everything about them. You'll probably be killed by cancer from all the benzene inhalation to top it off I don't like them.

 

I'd just run any foam sausage filter, get the carbs angled right, twist the motor on the mounts a bit can help or skim the inlet manifolds. Socks are a disturbance on the trumpet inlet, directly on the rim, about the worse way to setup the carbs. If it was setup on the rolling road and you added the socks after they would modify the fuelling a bit as they increase the depression on the venturi due to restriction; or a lowering of flow due to the air being totally shreaded as it enters the throat. Either way they suck and using them should be a hangable offense.

 

You want some nice space and air around the trumpet. I like foam filters.

 

If there is any smell of fuel inside the car when running it's not nice thats the main reason to avoid trumpet socks.

[RealWorld]

Not keen on Webers then...

 

Disadvantages of DHLAs is having to start from scratch on fuelling - parts and RR time - and finding the bloody things.

 

But here are some 45s:

http://cgi.ebay.co.u...3#ht_500wt_1014

 

And here are some 40s:

http://cgi.ebay.co.u...46#ht_577wt_999

 

I'm guessing that 40s would be pushed for race applications.

[mattius]

http://www.ebay.co.uk/itm/Twin-40-Dellorto-Carbs-and-inlet-manifold-/230724678032?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item35b8433190#ht_500wt_1287

[RealWorld]

Mmmmm - crusty Matt!

[nutos]

Have just finished fitting and tuning a set of 40mm mikunis on my little 1300 and it LOVES them. once you get your head around how they are tuned they very user friendly and soooo much cheaper than webers.Plus they look very cool.

I would love to see some dyno comparisons though.

[James]

Nutos— I'm sure we'd all love to see and hear about your install.

 

[nutos]

Yeah no worries,

Decided years ago as a teenager that I would have to own a spitfire after seeing own in a servo. Years later after doing lots of other modified(hot rodded) cars I was ready to buy and build one. I bought a 74 Mk4 that had been pulled apart 4 owners previous. A mate of mine that a had a quick herald 20 years ago suggested doing a bike carb conversion,

the seed was sown and became somewhat of an obsession. SUs although are cool and can perform well with the correct tuning and modifications just dont have that raw induction that I wanted. Weber and Dellortos would be great but down here in NZ they are bloody expensive for second hand let alone new ones.

So first I had a mate of mine with a profile cutter do the inlet and exhaust plates, this worked out well as I built my own 4-2-1 headers as well. Next I got some stainless pipe to match the plates and cut and pasted them with a Mig welder to fit the 40mm mikuni BST carbs that I found on trade me ($250). I had to flare the carb ends to fit so a friendly bloke at the local exhaust shop was able to oblige.

I initialy used a modified TC2000 air box with bigger inlets but found that it was too restrictive.So usede individual pods instead.

Tuning was a boon to say the least although now after hours upon hours online I have it pretty well sorted.

1. restrict fuel pressure to at least 3 pounds using fuel pressue reg

2.get the float levels RIGHT!! all else will fail if these are incorrect.This dictates throttle response as well as the whole scale.

3.tune the main jets I found 150 was a good start and alter from there.This dictates wide open throttle.

4.tune needle heights. off idle to WOT

5.pilot jet . Idle and progression.

[Nick B.]

There are many DHLA's on german ebay.

 

Usually they sell at about 150 - 200 euros.

 

Cheers

Nick

[RealWorld]

There are many DHLA's on german ebay.

 

Really? Wow, I'm loving internationalism today

 

I'll take a look. Nick, would you be able to do some translation for me if I need to ask questions or understand description details?

 

Thanks

 

R

[Nick B.]

I'll be happy to do some translation for you. I am not that good with german, but do get it somewhat right, usually using google translate to work from.

 

I have good experience with german ebayers - seems very honest, and always wrap things up very neat. Postage isn't to dear either.

 

Just checked german ebay now, but it appears the selection is somewhat - eeerm. Well, there is nothing today. Better make a search agent :-)

 

 

 

Cheers

Nick

[JohnD]

I'm no Weber expert, but a pair of 45's on a 1300 Spitfire?

Even if you are aiming at 8000 rpm, isn't that over-sized, when you will need a ?35mm choke?

 

John

[RealWorld]

 

Iisn't that over-sized, when you will need a ?35mm choke?

 

The main chokes on the old 45s were 36mm so mmmmmm....

[mattius]

Seems kinda counter productive paying for the larger 45s using that size of choke

[spitNL]

Hi Richard,

 

There are a few Dellorto's on the Dutch marktplaats:

http://kopen.marktplaats.nl/search.php?xl=1&ds=to%3A1%3Bdi%3A%3Blt%3Azip%3Bsfds%3A1%3Bpt%3A0%3Bmp%3Anumeric%3Blx%3A159256%3Bly%3A377339%3Bl1%3A2600%3Bkw%3Adellorto%3Bosi%3A2&ppu=0&postcode=5581HJ&p=1

Perhaps easier with google translate:

http://translate.google.com/translate?sl=nl&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fkopen.marktplaats.nl%2Fsearch.php%3Fxl%3D1%26ds%3Dto%253A1%253Bdi%253A%253Blt%253Azip%253Bsfds%253A1%253Bpt%253A0%253Bmp%253Anumeric%253Blx%253A159256%253Bly%253A377339%253Bl1%253A2600%253Bkw%253Adellorto%253Bosi%253A2%26ppu%3D0%26postcode%3D5581HJ%26p%3D1

 

Let me know if I can be of assistance.

[RealWorld]

Thanks Frederick, and good to see you back here!

 

The 7th item down in that list, in Uden looks tidy.

 

What's the deal with the price? Are they 275 euros or is it an auction with a reserve?

 

Would you be able to ask the seller for exact model numbers?

[Nick B.]

Very tidy. To me they appear to be emissiontypes.

 

Cheers

Nick

[spitNL]

Thanks, finally got my internet sorted after moving.

 

7th down the list, so that's this one:

http://auto-onderdelen.marktplaats.nl/oldtimer-onderdelen/511363884-set-gereviseerde-dellorto-40dhla.html?return=eJwtjc0KgzAQhN9F0KPmB7VGpOip9C2CSTEYzWIitS1992apl92Z2W8ZKaj4GEFaLxilIvFabuPUTiGAKIrZgV7zRW5zACtl8Plqiz%2BSwwTXw3Y0U74LLuU9Tflg4%2BhZRUjUykSNWYj7bSBK%2F1D%2BJAFTxJZ46Nd90ZsZkT4QKBtWVuhe0fG65rzBn%2F38mZ9RKG2t27B6cB67WAawdyQD58PolO7K8kJv96T9%2FgDw3EUk&df=1&fta=eNotkEluwzAMRe%2BiRdaabVHwvuiiVwiowa1RJRIiO3Eb5O6Vku4e8D7BTyIMcK8wAtku6XjFVImtwJgBsqeJHUKd1gzMJgZcU2rDAjat8LsUW%2BfQkrasQO2pwHk7xcvibdqBKcOVtukHxDAIYWzZWub7BiGmlC9rtrkuwA%2BlbBM9lFxXn0OclBrZ23vfL4EU%2FIzELm1BBQFkCa9ioikWvZFM8p1FhwOVtIMUGk0HoaVjDYyO6LoalXNKNBjQO%2B6f4Jju49pEM%2FcpPXg59wyPs%2FNdcRml7orhiNztLDiUMnQYg%2FOoXnWArLlgqMcUz5%2FrV29Mm2jvO%2BF%2B7Ee03uF5BQeCN2I%2F%2FvFKLAKF%2B%2BPxB8Frdxk%3D&fta_ind=7&fs=1

 

I agree they do look nice, the advert says they've been rebuild and cleaned inside and out.

Don't know if it's the correct word, but they have been blasted with glass beads.

Doesn't say which model unfortunately.

 

The price of 275Euro's is an asking price, so you can make him an offer.

BTW Uden is only 20 miles from me.

 

I'd be happy to contact him, if you have any questions.

[spitNL]

Richard,

 

Weren't you looking for some Weber rampipes, these are full radius, look OK to me:

http://www.ebay.co.uk/itm/Weber-and-Dellorto-Carburettor-Intake-Trumpets-/200695705933?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2eba65714d

[RealWorld]

Thanks Nick - I want to avoid emission types if possible, harder to tune. But how can you tell if they're emissions?

 

Fred - would you be able to ask the buyer what he knows, and where they came from? I believe a view down the trumpet and past the butterfly would help...

 

Also, there's a set of 45s on Ebay UK:

 

http://www.ebay.co.uk/itm/160708433173?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648#ht_500wt_1149

 

Which are labelled 5228P and 5230A - they look original and sound but again, are they emissions?

 

R

[spitNL]

No problem, just sent him a mail.

[spitNL]

Just heard back:

 

The type is 40DHLA-H, came off and Alfa

 

Venturi - 30

Tube 7772.12

Main jet 132

Air corrector 160

Acc 40

Idle 58

Choke 58

But he's got other venturi's, jets, etc.

 

He's also send some more pics, I'll email you.

 

 

Fred

Edited January 4, 2012 by spitNL

[spitNL]

-H is the emission type, right?

 

 

Found some info Dave posted:

Type 1 the first DHLA40 (no letter after) if you like the DCOE of the DHLA family, but boasts superior atomisation and tuning ability to the extra research at Dellorto...This carb has an idle jet (which also runs the progression and adds mixture at cruising) that is not connected to the main jet stack, the idle jet operates on its own from the float bowl. Also the idle jet air feed for the emulsion tube is ot fixed at a set size like later models...The main jets run on their own from the float bowl like the idle's...This gives two seperate circuits that must be tuned for perfect overlap to get good cruise and pickup....This has the benefit on small engines and racing engines and hard tuned engines of giving the ability to make the idle jet progress long or short, you can bring the mains in early and cut back the progression on the idle jet air feed with differing jet holders with differing sized air holes, more air, bigger hole less progression....So you can tune this carb a million ways for million application, Fewsters just got a pair of these. They are the ulimate in tuneablity, they are also as a downside extremely hard to tune without a massive jet box or rolling road, cause they need to be bang on the money. This type of carb uses a .1 venturi which has a bigger pilot hole that the .2 and .3 (ill cover later), this means a bigger signal is generated in the venturi tube which gives a bigger signal (pulsing) to the main jet stack - the venturi feeds the main power circuit into the engine, the big jets. So the .1 vent can tuned to get on the mains right away from very low rpm and are super responsive to tuning, you can delay the vent by adjusting the tubes and air correctors on the main jet stack, so it needs more signal to start the stack feeding the vent or less setup the opposite way, so they can be tuned many ways also.

Type 2 DHLA40E - These are the same as the DHLA40 with seperate circuits and use either 1 or 2 venturi, they have extra progression holes for the idle jet, so the progression phase can be increased in length (over more plate angle) to suit production cars, and aid economy, real smooth runners when setup with lengthy progression. The 2 vent is just like a 1 with tiny bit smaller bore size to the signal tube, so they have fitted .2 often in the E model as they have extended the progression phase and using the .2 vent means they don't have to delay the mains as much as fitting the .1 vent, so making jetting easier and more responsive. The Elan +2 used these with the 1 vent as its punchy sports car, the Alfa's used 2 vent and fitted the E model to flagship models with lazyier owners, who like crisp but relaxed power delivery. Power is equal on both types and they can both delivery the same results.

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 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 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.

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 everyones tastes and requirements using Dellorto...

[RealWorld]

Thanks Fred - and I have the pics now too.

 

So they're emission type - according to Dave (I think) : easy to tune, clever design but not suited to extreme engines or race cars. Bugger!