Hi all,

Anyone know somewhere reputable in Aus I can get Weber venturis bored out to a size of my choosing? Aus places want crazy money (i.e. over $50 each, they are $15 in the US) for buying replacements.

Cheers,

Eden.

Haven't had any vents bored about, but why not just buy 'em in from the US ???



I brought in 4 x 38mm 44IDF venturi's and 4 x emulsion tubes from CB Performance a couple weeks back.... delivered in 6 days, and cost me under $200 AUD landed for the lot. Way cheaper AND faster than what the local carb specialists could do (once place told me 10 days to get up from Melbourne... what the !?!?)

The Aussie Dollar has come up a bit since then too... up over 88 cents at the moment... so it'd be even cheaper now methinks !!!

Yeah I was thinking that but i can't find anyone with 36 IDF vents. Lots of 40/44 though. Anyone you know that does them?

Give Holzl a call
or contact Alfa1750 on ebay??

What size you have now??

Hi Barry,

I've got 28s in there now. Planning a 1916 so I'm going to need maximum size. Weber place near me has 34s, which would be mighty thin I reckon, but they want $55 each and don't do exchanges.

The Alfa guy on ebay is a good tip.

Cheers,

Eden.

I've read in a few places that the venturi's from some models of 36IDF are interchangeable with ones from 40IDF's... no idea of how to verify that other than trying it... do you know anyone with a set of 40IDF's in their parts stash ???

Another option would be to run them without venturi's at all... seen pics of that being done on drag car's, so must be OK at WOT but dunno how streetable it would be...

Bud Pauge of Redline Weber (USA), told me that boring out venturis is a big no-no. Bud probably knows more about Webers than most, and he recons the air flow can be disturbed enough to upset the operation of the carby. I'm sure he is right, but I suppose they make a few bucks selling venturis.

Cheers, Greg

It sounds like a bad idea, to bore them out. I've got some Weber 32's bored out (only) to 34 and the shape is Wrong, and the machining has cut into the slightly porous cast metal, ie they are rough. I would never do it again. If you buy new ones, you can always go back to them if needed... or sell on to someone else. Why ruin good expensive Weber parts?

You've convinced me guys. No boring out vents. Now to find some!

Interested to know if they are the same size between 36 - 40, sounds unlikely to me given the thoat size is different but I've been wrong plenty of times before.

Oh - here ya go - try asking Gracey !!!



http://forums.aussieveedubbers.com/viewtopic.php?tid=61788 

It would be good if someone (not me) would start a thread on what is available for sale / swap / loan / wanted etc. regarding things like Weber bits. Vents., emulsion tubes, jets and so on are expensive, and quite often used once and then put away in a tin. I believe that the part you want is often sitting in a cupboard, or under a bench somewhere, not being used.

Cheers, Greg

Hey

I have a set of 4: 32mm venturis out of some 36IDF's I owned in the past.
Send me a pm if you are interested.

Cheers
Marcus

Interesting reads there Sides - really appreciate the info. My 36s are Italian so I'll pop out the vents and measure them this weekend. I actually made a venturi pulling tool last time I had to change them. Hopefully I can find it still.

Greg, sounds like a good idea - I have a bunch of stuff I'm not using at the moment.

Marcus, we'll see what else I can dig up, but I'll keep you in mind.

Cheers,

Eden.

don't bore them out. There is suppose to be a certain ratio between the diameter of the venturi and the throttle otherwise there wont be a negitive
pressure at the main jet nozzles. The consequence of boring them out is leaning the AF out throughout the entire rev range (except idle).

The venturi works on the exact same principal as the aerofoil (wing) You dont go shaving the top of a plane wing to make it fly faster? It wont fly at all.

On the plus side little bit bigger is fine, but dont go massive or it will do as above.

Hi, i can see no reason why you cannot bore them out to a larger size or make new one as long as you have a sample of the size that you need, i have been making them for years with no issues with the tuning, some of the originals that you get are very roughly die cast and have no real form of accurracy in there manufacture

Although I'm in the "get new ones rather than boring them out" camp, it's a personal preference really... if done PROPERLY (shape etc.) and if good quality metal to start with you shouldn't have a problem.

....BUT (and this is a big but)...

...as I've found out today after A LOT of runs on the dyno, changing venturi sizes can give you some very unexpected changes in your tune (read AF ratio). A bigger venturi doesn't just lean it out across the range, or even mid range or top end... it changes how most everything works, and how much it changes each aspect is dependant on everything else. Doing a venturi change, well you basically need to forget everything you thought you knew about tuning or jetting the carbs with the previous size venturis.

So yeah... my vote would be try to line up new bigger ones, and when the engine is all together and in the car do some comparison stuff. Depending on your cam, rev range, intended use, fuel, availability of jets etc.... the smaller venturi's may actually work better for you (or not).

Sides - that's why I'm sorting out the vent issue first, then do the rest of the jetting to suit.

Another plus with getting new vents is I can always go back to them if new ones suck. If bored out ones are no good then I'm up the creek.

Will keep this thread up to date with my measurements and hoepfully results.

Cheers,

Eden.

Yup, cool - sounds like you've got it covered then. Definitely keen to see how you go.

Venturi measurements are as follows:

OD = ~40.5mm
Height = ~36mm

Accurate to about .2mm or there abouts. The vents have a very small amount of play, they slip in and out quite easily and the aux vent holds them down tight.

Lost my puller tool BTW, had to use the screwdriver trick - at least they are not on an engine.

Alright, have had confirmation that 36IDF vents are the same external dimensions as 40IDF.

One thing you have to be aware of though is that becasue the throttle plate/butterfly is 36mm you cannot use vents biggger than 34mm otherwise the venturi effect is lost and they will run like crap.

Cheers,

Eden.

Cool - good to hear that little puzzle has worked out !!!

Good info to know I reckon.