Dell'orto 40 vs Weber 40

I am in no way mechanically minded, but I did buy some Dellorto 45's last year, and rebuilt them following the famous book for these things.
Pretty much identical carbs as far as I found out. Webers are more common in old competition cars, because of the period they were built, rather than being a better carb.
I seem to remember reading that the Dellorto has a greater choice of needles and jet sizes, or was it the tubes, I dunno - but it went along the lines of the Dellortos being slightly better to fine tune, because you have a greater choice.
I took mine to Tom Airey to rolling road. He has been working on carbed motors for years and even he didn't have much of an opinion either way......

I'm sure the books I have say the Dellortos are easier to fine tune as said above. I think you can only buy Webers new now. The DHLA Dellortos are not made anymore. Weber bits are easier to get hold of too.

This is great folks, just the sort of info I was after from experience.

When you say that the dellortos are "harder to get parts for" does this mean it will cost me more and more time to source bits?

I do have a pair of dellortos already, DHLA 40 F's which I'd like to whip in a new gasket set, re-fit the spindle quadrant on one (they were used on a VW on opposing banks) and then take to a recommended rolling road for setup.

What do people think, would I be better off selling those for someone who may want to use them on a VW, and invest in a pair of webers that have come off a similar sized inline 4 cylinder complete with linkage etc?

Any thoughts appreciated- thanks for the info so far

Bishi- if rolling roads and stuff struggle with dellorto parts then i imagine the solex licensed mikunis may be even harder to get bits for unless you know of somewhere that does them?

They're both pretty much the same. The dellorto as mentioned above are a touch easier to tune and you don't have to adjust them as often once they're on the car, but for some reason Webbers seem to hold their value better.

Parts for both can be found at www.dellorto.co.uk/ which used to be called Eurocarb (iirc).

No difference

weber has a true mechanical accelrator pump
dellorto has a diaphragm

weber made DCOE and IDF IDA range from 50s onwards
dellorto got in on the act later in the 70s
solex and mukuni make smilar as well

Weber and dellorto ranges come in 2 types
both made 36s only ever made as OEM carbs
both made 40s as OEM and performance range carbs
weber 45, made as performance range carbs but for OEMs and aftermarket...hence all the different series I.e 45DCOE13 45DCOE9
48s from dellorto have a 4th Wide Open Thottle enrichment circuit
big webers just depend on the acclerator pump jet spraying with out activation at very high speed low vaccum which achives more or less the same aim

performance range
have 2 threads on the idle jet holder and a seperate drilling to the bowel to feed the idle jet circuit
the idle air into the idle ject stack is dicated by drillings or push in air corrector in the idle jet holder
OEM range have the idle jet fed off the main jet well
have 1 thread and a rubber o-ring to seal the idle jet stack and the air into that part is dicated by a brass sleaved drilling into the carb top/case through to below the o ring. only way to change idle air is to ream it out or replace with smaller brass sleave.
pain in the butt but do able

OEM range from emssion controled vehcile are more likely to have idle mixture screw in a cast in tower which is more likley to be siezed solid.

OEM range more likley to have idle air throttle plate bypass circuit and the adjuster for this will be capped over once set with solder (just pick it out with a screwdriver)

i'd choose cheap OEM carbs off an alfa or some such if I was putting them on a smilarly sized engine with similar rod ratio and operating RPM range..

eg 1500CC alfa boxer weber dellorto or solex are ideal for 1500-1641cc VW boxer engines with nout much but 1 place up on the venturi and a change of idle jets...

you can get ventruris for weber 45s in odd numbers I have a set of 35 mm venturis and 1 in 39 mm

the lack of range of accelrator pump jets on the weber front is accounted for by the fact that the pump inlet has a check ball valve. the gap in pump jets from say 45 to 50 is accounted for by the leak back drilling in the check ball valve I.e you fill in the gap 46 47 48 49 by choosing a check ball valve with a bigger smaller or no hole in its side. thus getting a rnage from 45(no hole valve through a range of holes with the 45 jet up to 49 then 50 again with the no hole valve)

pump stroke adjsuted on dellortos by threaded rod
adjsuted on weber by a new pump slide or brazing up the one you have

weber cold start choke mechanism wares out and dribbles but as you don't need it it can be blocked off with grub screws in from the bore
dellorto cold start choke mecanism if disconnected must be jammed into the off position inside the carb with a cut down biro cap or similar or it will jump up into the on position at the first backfire and wash the bores

thats about it really

solexs in 40 and 45 mm are the best quality but unless you speak german or have a yard full of old mercedes to nick parts off are a complete pain to get spares for

for mikuni look to japan and the US Mikuni in 45 is a favorite of the harley tuner.

entec(us importer) of OER (J/chinese weber rip off) also made weber copies...never seen one but standard weber carb parts fit

Dave

PS eduardo weber invented this style of carb.....but I still like a dellorto better

PPS closest thing you will get to fuel injection without injecting fuel..... gunson colour tune for idle stehescope for balancing duties a wideband for progression to Wide open and a selection of too small jets and a jet reamer to make tuning less of a financial burdon....

Dave

That book is good.

Loads of places sell Weber parts, very few do Dellorto.

www.dellorto.co.uk

should have most if not all the bits you need

Dave

all you can do is give it a go....

i ran 36mm with 28mm choke on a vw splitscreen van with a High CR 1641 cc standard parts bin special with 1300 sized valves

ran perfectly..masses of torque which was the aim so i could pull the long gearing in the 1303S beetle box i had fitted and the odd rice pudding skin

wasn't exactly an RPM monster but i could wind the thing up to a displayed 90 mph with a trailing wind..well i did until i snapped the crank clean in half

would guess the rpms died off at 4750

you'd be wanting to spin yours to i guess a more performnace orientated 6000 + i'd guess

40s with bigger chokes and up the mains and idles.

6000 rpm you need 34 mm chokes on a 400cc cylinder
7000 i'd guess 36

pays to be conservative 32 would do as nobody drives at wide open throttle on the street for more than 1% of the time

this is based on weber

Time that by 4 to get 130 mains
+60 for air correctors = 190 air corrector

if it pops and farts on run-on and tries to blow up your exhaust your idle jets are too small

this is basic rule of thumb


you can get round the lack of adjustemnt on idle air through the idle circuit by over cooking it on the idle jet and using the throttle air bypass circuit that the alfa carbs have. it may be a bit wonky into progression as the mains don't come in till something like 2500....but it will be driveable perhaps just not as crisp down low as you'd hope....even so it will be better than most without this kinda carb

just remeber that if you put in a longer duration cam

anything you know about the prescribed initial advance and the ignition curve goes out the window...the book will be wrong cos you change the brain of that engine

kick back test to establish initial idle advance so you don't get a black tail pipe
then set the carbs up....you must get the ignition timing correct first for idle before you have a chance in hell of getting the idle mixture bob on. do this by advancing the initial timing until the engine kicks back at your starter motor when you try to start it then take out 2 degrees)
then check full ignition advnce at 3000+ rpm
if it strays up past 34-36* with vaccum diconnected and blocked get the distributor recurved, or solder/braze up the weights so they can't advance as much

you new initial + the standard amount of mechanical advance in your dizzy will probably mean too much total at mid rpm....it will need to be pulled back in by modifying the Dizzy.

if its an automatic there are things that can be done with the vaccum advance plugged into unported vac source to get round the need for this at idle.....but i wouldn't do it on a manual.

Dave

Thanks for taking the time to write that little lot out

There is a programme I have for either dellorto or Weber which you can input your cyl capacity and peak rpm and it will advise jet and choke sizes - done by another clever man called Dave