OK guys, I realize you all have beat almost to death the deficiencies of the v6 intake system and have probably eliminated what I am about to say as "too expensive,'" and I hear you. But...the weber 3 barrel downdraft (yes like on the earlier 911's) on two sides have great appeal ( I know they cost more than a fixer Fiero). Has anybody been fortunate enough to try them? Seems like despite their vertical height they could be "manifolded" direct and eliminate the two piece intake. These are the IDT series and used to appear on some Corvairs, but today I could not see that the Corvair suppliers offer them any longer, including OTTO. I did find some on a restorers site for 911;s. Fun to dream. I lived with side draft DCOE's on a four and they were things of beauty.
I still cant figure out why ANYONE would want to goto carb from FI....
Are you kidding? No computer, no programming, no oxygen sensor, no cat, no injectors, no MAS no MAP, you can fix it with a pocket knife and pliers and it will run forever. Larry
I still cant figure out why ANYONE would want to goto carb from FI....
JMO...
Normally I would agree, but the Weber carburetor is a jewel of precision and available with an array of mainjets, air corrector jets, slip in chokes (bores) , but cost like jewels too. Installation would give direct and downward intake with no starvation . We still may hear from someone who inherited an estate with these great carburettors. I would start tomorrow if I could justify the cost. Just for fun.
Lots of dyno testing on what makes the most HP. TPI is at the bottom of the list. A well tuned carb makes more HP and an aftermarket TBI (such as FAST) makes more than a carb. The carb is the least efficient and gets less mileage than the others. I like the simplicity of a carb. Unfortunately most people no longer have the knowledge necessary to tune them properly. What's an air bleed? Transition what? Float level? It is a lot easier to look at a lap top and make adjustments. I have used a number of 2 bbl sidedraft webers. They are so simple to tune. Spendy but a little piece of heaven. Think outside the box - it's where the fun is.
My 2.8 was carb'd and picked up about 25 hp in the process at the wheels. Reason? The carb and intake flowed way more than the OE intake, and the carb is actually just a fuel mixer feeding it.
My 4.9 in it's OE configuration makes 200 hp and 275 ftlbs at 1700 rpm, but, it falls down badly after 5000 rpm.
With a carb, it revs merrily up to 6000 rpm without faltering or fading, and it out pulls my 290 ft lb Centerforce II clutch which will have to be replaced with a 417 ftlb clutch.
Arn
My carb'd 2.8 got just as good gas mileage with more power
[This message has been edited by Arns85GT (edited 08-28-2013).]
Arns, yes. I am somewhat a "greenie" as all my cars are emission oriented with cats...but I get weak thinking about some gnarly Weber trumpets atop the lowly 2.8. There is a you tube dude with a Covair on a 1/4 run supposedly with Webers. His top end is pretty as he overtakes a car that was either handicapped or hole shot him.
Lots of dyno testing on what makes the most HP. TPI is at the bottom of the list. A well tuned carb makes more HP and an aftermarket TBI (such as FAST) makes more than a carb. The carb is the least efficient and gets less mileage than the others. I like the simplicity of a carb. Unfortunately most people no longer have the knowledge necessary to tune them properly. What's an air bleed? Transition what? Float level? It is a lot easier to look at a lap top and make adjustments. I have used a number of 2 bbl sidedraft webers. They are so simple to tune. Spendy but a little piece of heaven. Think outside the box - it's where the fun is.
Woody
Woody so where do we find the estate sale with the cheap IDT's?
...the weber 3 barrel downdraft (yes like on the earlier 911's) ...
If it helps, I think the model number of those was 40 IDA 3 (40 mm venturis). Since they were originally fitted to the 2-liter 911 engine, 40 mm might be too small for the GM 2.8 (or larger). Other IDA models were available with venturis up to 48 mm, but I don't know if they were ever offered in the dash-3 (i.e. 3-barrel) versions. The dash-3 Webers were also fitted to some 6-cylinder Lancias and some V12 Ferraris, but they were always pretty rare objects.
[This message has been edited by Marvin McInnis (edited 08-29-2013).]
While not as good as FI, Webers are cool, but as stated, not cheep and those 3 barrel units should be out sight price-wase. When I could not find a pair of two barrel side-draft Webers for my 124 spider for under a grand, I made my own crazy intake and used 4 carbs from an 1100cc Haybsa -or however it's spelled- instead. I would still rather have the Webers for that engine
While not as good as FI, Webers are cool, but as stated, not cheep and those 3 barrel units should be out sight price-wase. When I could not find a pair of two barrel side-draft Webers for my 124 spider for under a grand, I made my own crazy intake and used 4 carbs from an 1100cc Haybsa -or however it's spelled- instead. I would still rather have the Webers for that engine
My GT40 kitcar had a Porsche drivetrain with those Webers. It was a nitemare to have adjusted right. It would drive fine, but idle was all over the place.
A little more thought and surfing... I woke up today and saw the port spacing on the 2.8- not equidistance I believe ,which detracts from my idealized short direct manifolding. I have not yet seen the height spec of the Webers but they would probably not nestle as low profile as I had initially hoped.Yes Mr McGinnis, The early carb was 40 IDA3C on the Porsche 911S and (I,m not an expert) concurrent with the first fuel injected 911s until '72? Finally hit a proper "keyword" if anyone is interested in internet sources ( "porsche 911 carburetor". ) There are not many , but divided into refurb of owner Webers and brand new replicas manufactured in CA by PMO @ $3500 the pair with kit for 911 and some others (not GM). Apparently the Solex/Zenith version also came into play , but is not as tunable. Weber no longer makes the 40 IDA 3C.
Rebuilt Webers run $2000 the pair and Solex $1500. There is a New Zealand listing for a pair of Zeniths for $495 plus $150 ship, several weeks transit, ebay guarantee. The sites show the 911 manifolding which appears about 3 inches long, but seems with the offset port config of the 2.8 it would require longer runners. The Weber sizing is smack in the middle of the 2.8-3.0 liter range and there are numerous site tables for tuning set up. Despite costing like a good, clean all-up Fiero there is appeal here. Each barrel can be tuned to its cylinder, but there is synchronization to contend with (Unisyn). It's been since 1967, but the DCOEs I remember were very stable and bullet proof. These are 2 barrel , side draft.
The commoner DCOE side draft are much cheaper and just as good except for fitment - about $495 each.
[This message has been edited by hobbywrench (edited 08-29-2013).]
The early carb was 40 IDA3C on the Porsche 911S and (I,m not an expert) concurrent with the first fuel injected 911s until '72?
The first fuel-injected production 911s were the 2.0 liter 1969 911E and 911S; the 1969 911T was still carbureted (Solexes, I think). I owned a 1969 911S for 15 years and 125,000 miles. The 1969 911E/S fuel injection was Bosch mechanical timed-indirect port injection ... very expensive but rock stable and quite effective when properly adjusted. Inputs to the Bosch mechanical injection pump were RPM, throttle position, temperature, and ambient atmospheric pressure.
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The commoner DCOE side draft are much cheaper and just as good except for fitment - about $495 each.
The DCOEs were available with venturis up to 58 mm, which were fitted to many of the early V8 CanAm race cars.
[This message has been edited by Marvin McInnis (edited 08-30-2013).]
Francis , Seems like your intake is still the sensible way to go if you still made them. regards, hobbywrench
In my somewhat biased opinion -and dyno proven- it is. The HP/RPM gains are quite cost effective. As for still making them, my back seems good enough -after surgery- to resume production. I just need to reclaim some our shop from my son's racing projects! He got another 1st place this year with his chump car.
Francis , Seems like your intake is still the sensible way to go if you still made them. regards, hobbywrench
In my somewhat biased opinion -and dyno proven- it is. The HP/RPM gains are quite cost effective. As for still making them, my back seems good enough -after surgery- to resume production. I just need to reclaim some our shop from my son's racing projects! He got another 1st place this year with his chump car.
Hope Francis is able to resume work in good health. Further reading confirms the inherent problems with so many mechanical parts in the carburetor...worn shafts, distorted bores, damaged diaphragms, worn butterflies, on and on. Very expensive to repair. Reminding us of the inherent superiority of fuel injection. Still these 3 barrel carbs beakon. I have asked the NZ vendor for bore spacing and will post if he answers.
Webers look great. That's the only reason that I can see for messing around with them on a 2.8. Performance wise there are so many better engines that we can use. I will say that a 2.8 with webers could be made into an awesome looking engine in a Fiero. The only way to make my ls4 look ok is to cover it.
[This message has been edited by dratts (edited 08-30-2013).]
Having done a carb'd 2.8 with some success, I can tell you that in terms of bang for the buck it is hard to beat Francis T's trueleo setup.
If I had known about it before I started carbing I probably would have bought it.
The thing about retrofitting carbs of any description to a MPFI engine is that it is far from simple and the parts do add up.
The biggest thing to attach to a 2.8 is something to make it breath better. Of course the porting and polishing and other stuff is necessary but, it is still a matter of getting more fuel mixture into the cylinders and evacuating them after the burn.
Francis T has that covered pretty well.
Good luck with the project though, because I like Webers too.
You could always try three two-barrel IDAs for the same functionality and similar appearance. A lot of V-12 Ferraris used this arrangement ... except with six carburetors to synchronize instead of three.
[This message has been edited by Marvin McInnis (edited 08-31-2013).]
This was the setup in my orange and black Fiero, but is now long gone and replaced with a turbo four cam V6 (2007 Saab 9-3 2.8t) that makes more power.
Tuning the Webers are not bad as long as you have patience and the correct tools. I used to work on cars with Webers all the time, but they seemed to have faded out for the newer models. Initial jetting, tuning and syncing will be the hardest part. Once that is done, yearly adjusting takes about 30 minutes.
All this talk of downdraft Webers and things still makes me wonder why there's not been any ITB injection setups recently. Couple of sets of 4A-GE 20V throttlebodies, some crafty linkage and engineering... hmmmm...
It is heartening to see there are dreamers like me out there. I love to look at sport bike engine designs like Aprilia etc the intakes are immediately above the intake ports and they use stepper motors to change the length of the intake trumpets. Wish I were not so old, arthritic, and cowardly , or I'd be on one as my final act, probably. Pick me up and remove me from the seat with a cherry picker.
Really , the US two and four barrel on the downdraft manifolds are probably close to the webers , except for pedigree and don't stick up any higher. Regards to all. hr
[This message has been edited by hobbywrench (edited 08-31-2013).]
Two things make these Webers desirable. You can change the jets without taking the carb apart.[ Wing-nut cover] The throttle shaft runs on ball bearings for longer life and better overhaul.
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