46 replies to this topic

[OfficeLinebacker]

Hey guys, I've recently been working on a car with a multiple Weber setup (four of them to be exact), and I've read a good bit about the venerated Weber. I have two questions:

First off, what was it about Webers that made them so great? "Easy to tune" is one of the phrases I hear bandied about. That and the fact that some of them work sideways.

The other question I have is, why multiple carbs instead of one big one?

This car has four two barrel carbs. Really it's essentially four pairs of synchronized carburetors. It's a pain in the ass to tune and I'm turning over the job of rebuilding them to someone with more expertise. One of the carbs in particular is particularly FUBAR. Seems like the procedure of linking up the throttles and chokes to make them all work in perfect sync, plus of course tuning each idle circuit individually, leaves a lot to be desired. So what's the payoff?

thanks!

[gruntguru]

Hey guys, I've recently been working on a car with a multiple Weber setup (four of them to be exact), and I've read a good bit about the venerated Weber. I have two questions:

First off, what was it about Webers that made them so great? "Easy to tune" is one of the phrases I hear bandied about. That and the fact that some of them work sideways.

The other question I have is, why multiple carbs instead of one big one?

This car has four two barrel carbs. Really it's essentially four pairs of synchronized carburetors. It's a pain in the ass to tune and I'm turning over the job of rebuilding them to someone with more expertise. One of the carbs in particular is particularly FUBAR. Seems like the procedure of linking up the throttles and chokes to make them all work in perfect sync, plus of course tuning each idle circuit individually, leaves a lot to be desired. So what's the payoff?

thanks!

The payoffs of one-choke-per-cylinder include
- Ability to "Wave" tune the intake
- Equal runner lengths
- Straight runners (potentially at least)
- uninterrupted runner per cylinder (no junctions)
- no fuel distribution issues (each cylinder has its own fuel metering circuit)
- reduction in "wetted" pipework
- one throttle per cylinder, closer to port

phew - I'm out of breath - I'm sure someone else has a few more.

[Tony Matthews]

phew - I'm out of breath - I'm sure someone else has a few more.

They look nice...

[gruntguru]

Oh - I forgot "What makes Webers so great"
- Quality! eg spindles on ball bearings
- Ability to adjust every aspect of metering (the key items can all be changed in seconds) - venturi, secondary venturi, main jet, emulsion tube, air corrector, idle jet, idle air corrector, power jet, acc' pump volume, acc' pump discharge rate, acc' pump duration, cold start/warmup circuit, needle and seat, etc etc

[DOF_power]

>
^ Compared to advanced electronic direct injection systems ?!

[gruntguru]

Compared to advanced electronic direct injection systems ?!

Even Webers don't come close.

[DOF_power]

Even Webers don't come close.

My point exactly.

[Bob Riebe]

Even Webers don't come close.

That depends on which end of the tow-hook one is; as wonderful as electronic fuel injection is at adapting to conditions on the run; without the computer to run them, they are as useful as teats on a bore.

I have seen carbs that run miserably but still keep the car moving; with the new systems that don't happen. No computer, no forward motion.

For every yin there is a yang, but with the price of gasoline today, unless one can afford it and knows the way around inside a carb., fuel inj. is pretty nice.

On the scale of carburettor greatness; how do the new Barry Grand carbs compare.

Edited by Bob Riebe, 27 July 2009 - 01:23.

[OfficeLinebacker]

Just for the record Aston Martin switched away from EFI back to carbs, Webers, to meet USA smog standards in the late 1970s

[imaginesix]

Just for the record Aston Martin switched away from EFI back to carbs, Webers, to meet USA smog standards in the late 1970s

I don't know, but that sounds like a condemnation of Lucas rather than EFI.

[cheapracer]

- Ability to adjust every aspect of metering

main jet, emulsion tube, air corrector, idle jet, idle air corrector, power jet,
acc' pump volume, acc' pump discharge rate, acc' pump duration,

If you know what you are doing.

I miss them a little, made me some good pocket money and drove a lot of interesting cars - damn you to hell EFI!!.

Edited by cheapracer, 27 July 2009 - 04:43.

[mariner]

Somebody once pointed out that if fuel injection had been the original air/fuel system on cars then the guy/girl who invented the carb. would have been hailed as an engineering genius due to the simplicity.

Seriously carbs had 60+ years of evolution on F.I and although Rochester, Bosch and Kugelfischer all brought out workable mechanical FI systems for road cars it was the advent of micro electronics that gave FI supremacy. Remember Bendix in the US had the complete basics of EFI way back in the 1950's but it was too big/costly/erratic so they sold it to Bosch ( big error profit-wise!).

[GreenMachine]

... I have seen carbs that run miserably but still keep the car moving; with the new systems that don't happen. No computer, no forward motion. ....

I thought that a 'limp home' fallback was standard on all ECUs?

Wouldn't necessarily help in all circumstances, but same applies to a carb too (I presume).

[JtP1]

I thought that a 'limp home' fallback was standard on all ECUs?

Wouldn't necessarily help in all circumstances, but same applies to a carb too (I presume).

My experience is more "limp to the side of the road" mode.

[GreenMachine]

My experience is more "limp to the side of the road" mode.

My sympathies

[gruntguru]

QUOTE (OfficeLinebacker @ Jul 26 2009, 22:02) *
Just for the record Aston Martin switched away from EFI back to carbs, Webers, to meet USA smog standards in the late 1970s

I don't know, but that sounds like a condemnation of Lucas rather than EFI.

The injection was actually Bosch mechanical. Aston Martins fitted with the system suffered from a number of problems which drove the switch to Webers:
- Hours of painstaking factory assembly and setup
- Very difficult and time consuming to tune
- Poor idle and low speed driveability
- Cost and availability

Edited by gruntguru, 29 July 2009 - 00:11.

[gruntguru]

I thought that a 'limp home' fallback was standard on all ECUs?

Wouldn't necessarily help in all circumstances, but same applies to a carb too (I presume).

Limp home mode is a feature of later digital systems.

Bosch CIS and CIS-E were mechanical injection systems (the E version had a digital computer doing the fine trimming) which could fall-back to mechanical operation if the ECU failed. Mercedes continued using CIS for many years - probably for this reliability benefit.

(Bosch CIS is totally unrelated to the early mechanical system used on Astons)

[JtP1]

One of the major problems of early ECU ignition systems was the cost of programming. Ducati used a complete electronic ignition system on one of their bikes, iirc in the 80s. The bike returned to points and bob weights the following model year, as the cost of reprogramming the system for the modified model was totally uneconomic on the size of Ducati production runs. Obviously systems are much easier to reprogram now.

[gruntguru]

One of the major problems of early ECU ignition systems was the cost of programming. Ducati used a complete electronic ignition system on one of their bikes, iirc in the 80s. The bike returned to points and bob weights the following model year, as the cost of reprogramming the system for the modified model was totally uneconomic on the size of Ducati production runs. Obviously systems are much easier to reprogram now.

The main "time cost" in remapping ignition advance is the large number of map locations required if the system is to be tailored to the exact timing needs of the engine - timing maps viewed as a contour map are very "rugged terrain", full of peaks, dips and discontinuities. Reverting to a mechanical timing system to "save" this time is farcical. If the reprogramming was done in large "blocks" equivalent to the capabilities of a mechanical timing system, the process would be very quick - much quicker and cheaper than tailoring a set of springs and bob-weights.

I can only assume that Ducati were in a situation of paying a third party (Marelli or Bosch) to do the reprogramming and hence the high setup cost.

[cheapracer]

One of the major problems of early ECU ignition systems was the cost of programming. Ducati used a complete electronic ignition system on one of their bikes, iirc in the 80s. The bike returned to points and bob weights the following model year, as the cost of reprogramming the system for the modified model was totally uneconomic on the size of Ducati production runs. Obviously systems are much easier to reprogram now.

It was Italian electrics of the 70's, need I say more?

Every weekend back in the mid 80's I would ride my Yam RZ350 with my Ducati Mates and every weekend one of them would have an electrics problem. From what I could tell from their info the early electronic ignitions had 3 steps of advance as the revs rose switching through individual wires to the blackbox and sometimes to get home they would tie all 3 wires together hoping one of the circuits would work. And we always made sure to get home before night too - and people think Lord Lucas was the Prince of Darkness....

Oh and by the way, Dukes became real bikes when they went to Japanese electrics and Japanese carbs - the Spanish Bike Companies should have taken notice because Motoplat and Anal carbs killed them. Never take a pit place next to a Bultaco, Ossa or Montesa owner unless you like pushing bikes up and down pits.

Motoplat CDI = Consistently Doesn't Ignite

Edited by cheapracer, 29 July 2009 - 09:55.

[Tony Matthews]

Anal carbs

Were they for rear induction?

[cheapracer]

Were they for rear induction?

That was no mistake, don't know anyone who works on them to use "m" rather than "n"

[Bill S]

I used to run Weber DCOE 45's on my racer, but it always had a nasty rich spot in the mid revs that we couldn't cure.
The fix was to fix four Mikuni 38 flat-slides, modified a bit with an additional power jet.
http://www.billzilla.org/racrep18a.jpg

The Webers were nicer to run at low revs and easier to balance, but the Mikuni's are better on that engine. The same carbies on the old Toyota 3K 2v engine worked perfectly though.
Anyway, these day I muchly prefer full digital management, it's far easier and my laptop works better than any screwdriver.

[McGuire]

Remember Bendix in the US had the complete basics of EFI way back in the 1950's but it was too big/costly/erratic so they sold it to Bosch ( big error profit-wise!).

Seemed like the thing to do at the time. In 1961 the unit cost of a carburetor was like seven dollars while EFI ran into the hundreds. After six or seven years of development it looked pretty hopeless. Bendix failed to fully foresee 1) microprocessors and ICs that would lower unit costs to a fraction; and 2) emissions standards and escalating fuel prices driving demand for the system. The company still made a nice pile of change on the licensing. Positive revenue flow, it's all good. Any loss was in opportunity cost. Corporations make decisions for strange-looking reasons that often come down to risk management. Supplying the OEs is a tricky business at best.

[McGuire]

If an OE had jumped on board Bendix would probably have stayed in.

Edited by McGuire, 29 July 2009 - 13:57.

[JtP1]

Anal carbs

Would they be downdraft?

[rollover]

Never take a pit place next to a Bultaco, Ossa or Montesa owner unless you like pushing bikes up and down pits.

Motoplat CDI = Consistently Doesn't Ignite

In the early 70's I sold my Ossa for a CZ. Shortly thereafter I became so aggrivated with bikes I went back to Mini Coopers. I have shelves of Weber bodies,parts and jets but love the SU' for simplicity and reliability.

p.s. I still have points in my car so I can fix them on the side of the road!

[gruntguru]

In the early 70's I sold my Ossa for a CZ. Shortly thereafter I became so aggrivated with bikes I went back to Mini Coopers. I have shelves of Weber bodies,parts and jets but love the SU' for simplicity and reliability.

p.s. I still have points in my car so I can fix them on the side of the road!

I have electronic ignition so it never needs fixing!

[rollover]

I have electronic ignition so it never needs fixing!

We repair electronic ignitions when they are TOWED into our shop! Ford coils and camshaft potion sensor syncronizers, Honda distributors, GM modules, when they crap out a tow is the only way to go.

[Terry Walker]

I had an Alfa 1750 GTV, the elegant Bertone coupe, for 17 years. When I bought it, the owner had just had the two horzontal Weber carbs set up after a rebuild, and I never touched them again. Wonderfully reliable and always hed their tune. I have had several SU carbed cars, and much as I love SUs, they do need plenty of TLC to keep them optimum, but luckily I knew an ace mechanic who also loved SUs and truly understood them, so my SUs got maintained correctly.

[gruntguru]

Anal carbs

Energy food for dung beetles.

[Tony Matthews]

Energy food for dung beetles.

[gordmac]

The Bertone Alfas used to come with either Weber or Dellorto carbs. Apparently the Dellorto ones had slightly better engine output and economy.
David Visard used to build Dellorto bits into Webers on engines homologated with Webers.

[gruntguru]

The Bertone Alfas used to come with either Weber or Dellorto carbs. Apparently the Dellorto ones had slightly better engine output and economy.
David Visard used to build Dellorto bits into Webers on engines homologated with Webers.

I think the merits of Dellorto vs Weber varies from engine to engine. I remember one fairly exhaustive comparison on the same engine (I think by Vizard) where the final outcome was a small power advantage to the Webers and a small economy advantage to the Dellortos.

[NRoshier]

No one mentioned the noise...webers sound great!

[cheapracer]

No one mentioned the noise...Webers sound great!

You got that right as well as Dellortos and the not yet mentioned Japanese Solexes.

I had a hand in setting up the Weber 48's on the works Rally Oz Nissan Stanza's way back then replacing the Japanese supplied 50 Solexes that came on the engines from the factory. The Solexes flowed better and were worth 10hp but they came with little in the way of tuning parts. Before I went OS I still had some Solex emulsion tubes from those days still sitting in my toolbox.

I had a go at setting up a few Solexes that came standard on early Toyota Twin Cams, 2TG's, 18RG's and others but without key spare parts it was a bit useless.

Edited by cheapracer, 30 July 2009 - 13:52.

[bigginge]

Did someone say Weber carbs [I know, late to the party].....

[JtP1]

The Bertone Alfas used to come with either Weber or Dellorto carbs. Apparently the Dellorto ones had slightly better engine output and economy.
David Visard used to build Dellorto bits into Webers on engines homologated with Webers.

I had a friend who fitted a Dellorto to is mini rather than a 45 DCOE, because the Dellorto had bigger butterflies. I asked if it was really worth the effort when the Weber was a simply read the book and fit the jets and chokes, but hee reckoned there was the advantage of the bigger butterflies.

But you're only using 38mm chokes instead of the 40s you can fit in the Weber with no problems. But the butterflies are bigger! Bet his amplifier goes to 11!

[cheapracer]

Did someone say Weber carbs [I know, late to the party].....

FIAT X1-9 I presume as the FIAT 128 engine (which I reconise) slopes forward as to the radiator in a 128 and that engine is sloping forward to the firewall?

Yes many forget DCNF's (downdrafts) when talking about Webers immediately thinking of DCOE's (sidedrafts) even though many a Ferrari and Lambo etc. had DCNF's.

And whats a Mazda 13B Rotary without a 48 IDF feeding the PP!

[bigginge]

FIAT X1-9 I presume as the FIAT 128 engine (which I reconise) slopes forward as to the radiator in a 128 and that engine is sloping forward to the firewall?

Yes many forget DCNF's (downdrafts) when talking about Webers immediately thinking of DCOE's (sidedrafts) even though many a Ferrari and Lambo etc. had DCNF's.

And whats a Mazda 13B Rotary without a 48 IDF feeding the PP!

A wise and educated man!

Edited by bigginge, 05 August 2009 - 08:29.

[Melbourne Park]

FIAT X1-9 I presume as the FIAT 128 engine (which I reconise) slopes forward as to the radiator in a 128 and that engine is sloping forward to the firewall? Yes many forget DCNF's (downdrafts) when talking about Webers immediately thinking of DCOE's (sidedrafts) even though many a Ferrari and Lambo etc. had DCNF's. And whats a Mazda 13B Rotary without a 48 IDF feeding the PP!

I had an X1/9 ... but I didn't recognize it from the picture.

Were those Nissans you worked on the 710s? With the geared overhead cams (no belts or chains)?

Edited by Melbourne Park, 25 August 2009 - 13:05.

[cheapracer]

I had an X1/9 ... but I didn't recognize it from the picture.

Were those Nissans you worked on the 710s? With the geared overhead cams (no belts or chains)?

No, Stanza's - the 710's were mostly Jap factory only, not to be touched by mere Ozzies without 6 letters of permission signed in blood and in triplicate. Anyway, I was never an actual member of the team just an outsource. Bastards wouldn't even give me a shirt on events!

The LZ motor was an abortion of gears and sprockets (about 10 all up I think, I never did work on one internally) with a short chain for the cams at the top. Took them a while to get them reliable but to their credit they rarely stopped once they got there. Look at their Safari record.;) A couple were running in Datsun 1600's through the 80's under Group G, sounded great still.

Did you ever see a 710's exhaust under the bonnet? Magnificent, bloody art is the only way to describe the 4 long headers curling first up, then over and under.

[Ian G]

No, Stanza's - the 710's were mostly Jap factory only, not to be touched by mere Ozzies without 6 letters of permission signed in blood and in triplicate. Anyway, I was never an actual member of the team just an outsource. Bastards wouldn't even give me a shirt on events!

The LZ motor was an abortion of gears and sprockets (about 10 all up I think, I never did work on one internally) with a short chain for the cams at the top. Took them a while to get them reliable but to their credit they rarely stopped once they got there. Look at their Safari record.;) A couple were running in Datsun 1600's through the 80's under Group G, sounded great still.

Did you ever see a 710's exhaust under the bonnet? Magnificent, bloody art is the only way to describe the 4 long headers curling first up, then over and under.

OT for a moment, the 710 Motors were rebuilt by Aussies at the 1973(74?) Southern Cross Rally at Port MacQuarie,i was standing there watching them, young(late teens early 20's) blokes from Melbourne,the Jap mechanics and their white gloves all disappeared. I asked one(was that you?) what happened and all he said was "Oil" but a Journalist who was also there heard that 2 of the 3 cars had "run there bearings". Great Rally Car,looked good,sounded good but no match for an Escort except in the real rough stuff.

[cheapracer]

OT for a moment, the 710 Motors were rebuilt by Aussies at the 1973(74?) Southern Cross Rally at Port MacQuarie,i was standing there watching them, young(late teens early 20's) blokes from Melbourne,the Jap mechanics and their white gloves all disappeared. I asked one(was that you?) what happened and all he said was "Oil" but a Journalist who was also there heard that 2 of the 3 cars had "run there bearings". Great Rally Car,looked good,sounded good but no match for an Escort except in the real rough stuff.

Do you remember the rain? geez it rained, and rained .....

No that was before I was involved with them and I was there looking after my Dad - late works Honda Civic entry.

Dad was car 73 because of the late entry - 2 in front of another late entry, car 75 someone named Colin Bond in an XU1 ;)

Dad waited all afternoon and night for Bond to nail him but he never did - he was leading Class A by a mile over Bill Evans in the Datsun GX1200 and at the end of day 1 was in 11th outright in a bog standard Civic - the names and cars in front of him were incredible as you would know, Factory 710's, 240Z's, Lancers etc. something I'm quite proud of him for.

Maybe it was trying to go fast to stay away from Bondy that gave him the speed!!

Alas the car broke a front caster rod the next day and he couldn't get out of stage because they couldn't keep the CV from popping out of the gearbox. Note that those very first Civics had a welded on caster rod (to the LCA) and very shortly after had a bolted on type so maybe competition does improve the breed - sad it was my Dad who had to find it.


Hmm I was just remembering more - the Reliant Scimitar, the Hodgson Falcon, the yellow Porsche, J Sihng and his funny hat (nice guy).

Edited by cheapracer, 26 August 2009 - 02:34.

[Ian G]

Do you remember the rain? geez it rained, and rained .....

Sorry wrong Year,it was 1975 i was recalling with the 710 engine dramas,very embarrasing for them. 1973 & 4 were wet and 1976 was the year of the factory Escorts( Makinen & Clark).
1976 was the last SC we attended after 5 in a row, i saw last Year they are trying to restart/reform the original ASCC ,not sure how it went.

Trying to place the Honda,i'll dig out some old magazines.

SORRY about OT.

[cheapracer]

Sorry wrong Year,it was 1975 i was recalling with the 710 engine dramas,very embarrasing for them. 1973 & 4 were wet and 1976 was the year of the factory Escorts( Makinen & Clark).
1976 was the last SC we attended after 5 in a row, i saw last Year they are trying to restart/reform the original ASCC ,not sure how it went.

Trying to place the Honda,i'll dig out some old magazines.

SORRY about OT.

No problem for me!

Hondas plural..

There were 4 Civics - Captain Peter Janson in the RS1300 (was running 6th outright and damaged the side of that mentioned yellow Porsche when passing it in stage then it got a hole in the radiator and boiled) and 3 Class A cars one being a Girls team. Dad didn't want to run to begin with because they told him they were running 360cc Honda Life's!! (hence the late entry when they finally changed to Civics but he still didnt believe them until he actually got the car a week or so before )

Yeah I was there in '75 just looking and we met George Fury and Monty Suffern walking out after their 710 stopped about 10kms in and George was, err, pissed and I don't mean angry! They always kept a bottle of "insurance" in their car as Monty called it. Monty used to tell the Japanese that it was a bottle of petrol so in case the fuel pump failed they could run a siphon hose quickly from that bottle to get out of stage Monty likes to tell the story as they were walking out (in the middle of the night in the bush of course) a Japanese crew in a Lancer stopped at a fork and were busy looking at their map, Monty walked over to see if he could help and when they saw him, they literally screamed and fled - hopefully down the right road!!

[Ian G]

I think i remember the Fury incident,IIRC they were were seen sitting on a rock in the middle of nowhere with a torch and a bottle of whisky. I won't mention his name or car but an international Driver,who withdrew on the first night, spent the next 4 days in the Travelodges Bar and created a ruckus every Night when they tried to close it.

Getting back on track,if anyone has any old Weber parts lying about in the garage Ebay is the way to go. When we were Rallying Datsun 1600's we purchased some Chrysler Charger 45's(cheaper from a Chrysler Dealer than the Weber agent) and had them rejetted/choked for the 1800cc Datsun Engine. I cleaned out my garage a couple of Years ago and put all the old Charger Jets/Chokes/ET's etc on Ebay thinking around $50 ,they went for nearly A$300 ,i am certainly out of date.

Edit...OT again...Early 710 Motor Exhaust.

Edited by Ian G, 06 September 2009 - 11:07.