TheWatson
TheWatson None
12/21/11 1:53 p.m.

I am being warned not to go this route. I have a "hard to find" stepped inlet manifold that allows for hood clearance. It requires 3 Weber 40 DCOE carbs. The warning I am getting (from knowedgeable sources) is that this setup is only satisfactory for racing (I'm not a racer). And that it will only function well at a certain RPM range. That is won't idle well. And that I'll need to make LOTS of other changes to the engine (CAM, distributor, fuel pump, headers, etc). Does anyone have experience with anything similar? I ultimately want a fast street car, but not (currently) looking at racing.

bearmtnmartin
bearmtnmartin New Reader
12/21/11 2:32 p.m.

You are right. You run the risk of excessive horsepower causing severe driveability and handling issues. Best thing is to just sell your step manifold to me for my race car. ...

Tom Heath
Tom Heath Web Manager
12/21/11 2:37 p.m.

You might find better Triumph advice on the other side of the fence at ClassicMotorsports.net.

foxtrapper
foxtrapper SuperDork
12/21/11 2:41 p.m.

A whole lot of DCOE's do run the way you were warned. People get them too big, leave the choke tube in them too large, and don't have the money to buy all the jets necessary to dial it in correctly. So they run around, broke, with a lousy running car, and blame the DCOE for it.

Getting a stock manifold and setting SU carburetors on it will give almost the same peak horsepower as the DCOE's, probably a good bit wider power band, and be a whole lot cheaper to set up.

MG Bryan
MG Bryan HalfDork
12/21/11 2:47 p.m.

Foxtrapper hit the nail on the head. Weber's aren't something you just bolt onto a car and run with. Start with the right model of DCOE and tune the car correctly and there shouldn't be much in the way of drawbacks to the setup. I don't see the point of triple DCOEs if you're not doing anything else to engine though. That's a lot of money to spend if you aren't going to make the most of it.

BoxheadTim
BoxheadTim SuperDork
12/21/11 3:02 p.m.
TheWatson wrote: I am being warned not to go this route. I have a "hard to find" stepped inlet manifold that allows for hood clearance. It requires 3 Weber 40 DCOE carbs. The warning I am getting (from knowedgeable sources) is that this setup is only satisfactory for racing (I'm not a racer). And that it will only function well at a certain RPM range. That is won't idle well.

That sounds pretty much like you'd expect a car to run that hasn't got the carbs set up correctly. Doesn't matter if they're SUs or DCOEs, it's just that DCOEs are harder to set up than SUs and there are fewer people who have that skill and the experience. Unless you want to spend a lot of time setting them up, the results might be as described above but that's not the fault of the carbs.

TheWatson wrote: And that I'll need to make LOTS of other changes to the engine (CAM, distributor, fuel pump, headers, etc). Does anyone have experience with anything similar? I ultimately want a fast street car, but not (currently) looking at racing.

I would think they're probably overkill for your engine as it is at the moment, but that shouldn't prevent the from working. To get the most out of it, yes, you can build a really hot engine and still use the same carbs but if the carbs are set up right, you can use them on a stock engine, too.

Now given the cost of 3x DCOEs it might be debatable if it's a good idea or not...

Of course something I'd suddenly be tempted with is get a set of throttle bodies that fit a DCOE manifold and megasquirt the car, but that might well be a rabbit hole too deep to go down in.

spitfirebill
spitfirebill SuperDork
12/21/11 3:06 p.m.

I personally would not waste the time and money to set up 3 DCOE webers. The cost to properly tune them using a rolling road and the necessary parts might scare you. i would rather go with the SU carb setup. But, I didn't know you could make them fit a GT6.

mad_machine
mad_machine SuperDork
12/21/11 3:43 p.m.

they may be a pain to set up, but you have to admit that triple webbers looks and sounds great on on a straight six. My father had a 260z with triple DCOEs.. I don't remember any drivability issues aside from having to be careful about giving it too much throttle below 2 grand. Open up the butterflys too much and it would choke on the air/fuel and backfire through the carbs. Made for interesting smoke from under the hood

Dr. Hess
Dr. Hess SuperDork
12/21/11 3:53 p.m.

3 DCOE's: $1500 (last I looked). Guess wrong the first time out and you have to buy 6 choke tubes, 6 emulsion tubes, 6 ... for each try. Now, if you have a BIG checkbook and really like the cool look, go for it. If you want better driveability and a wow factor, find 6 throttle bodies somewhere off something, like 1.5ea 4AGE 20v's or something, and megasquirt the thing.

irish44j
irish44j Dork
12/21/11 4:01 p.m.
foxtrapper wrote: A whole lot of DCOE's do run the way you were warned. People get them too big, leave the choke tube in them too large, and don't have the money to buy all the jets necessary to dial it in correctly. So they run around, broke, with a lousy running car, and blame the DCOE for it. Getting a stock manifold and setting SU carburetors on it will give almost the same peak horsepower as the DCOE's, probably a good bit wider power band, and be a whole lot cheaper to set up.

I second everything he said. I went the latter route due to what I'd heard about the triple DCOE setup, and instead went with SU 1.75's with a bored intake manifold (using TriumphTune adaptor plates). Tuning was super-simple and the car pulls hard through the entire powerband. Plus you can sell that stepped manifold for big money to racers, since it's hard to find these days.

Randy_Forbes
Randy_Forbes New Reader
12/21/11 6:25 p.m.

No, they're not for the faint of heart, or patience-challenged, but a Weber DCOE is just another carburetor. They were standard fitment on Alfa Romeos, some Lotus models and numerous other road cars. Given all their variables (I believe 68 such variables in a set of 3 DCOEs) they can be perfectly tuned to a given engine. Admittedly, it was with the help of an MSD ignition, but this baby will idle through stop & go traffic indefinitely. If you want them, don't let people that don't understand them put you off.

NOHOME
NOHOME HalfDork
12/21/11 6:37 p.m.
Tom Heath wrote: You might find better Triumph advice on the other side of the fence at ClassicMotorsports.net.

Or not...More traffic here. Sorting through internet advice is all about volume of answers and sorting the chaff.

DCOEs are great carbs. The biggest sin is that people go too big and dont have the vacuum signal to pull the fuel out of the jets fast enough. This results in the infamous Weber "Bog".

The other thing to consider with Webers is the cost of tunning parts. You will need a selection of jets, emultion tubes and venturies. There are two of each for each carb. figure when ordering, you want at least a range or two above and below your best guess for each part. How many carbs you getting? With an MGB, it is ussually a $100 bill each time you try to tune one in.

Don't even start until you have bought the book on how to tune webbers and then thought it through until you can do it in your head. seriously, if you dont know what you are dong, they will drive you nuts.

vazbmw
vazbmw Reader
12/21/11 6:41 p.m.

DCOE Webers are very tuneable. I ran them on my street/autox Toyota 20r/22r for years. You can make them high performance or economy carbs. I have not read all there replies, but changing out the venturi and jets you can make them work with any setup. That being said, I spent lots of money on jets etc to get it right. Weather and other things affect hp more than it would with efi.

Curmudgeon
Curmudgeon SuperDork
12/21/11 8:06 p.m.

Agree, DCOE's are very tuneable (that's what they were designed for) but it's time consuming. The chokes (venturis) are the key, though; once you have that right the rest of it's just swapping brass through the convenient little hole. For a street car, the chokes will have to be pretty small (probably 30's) for decent bottom and mid and this will of course hurt the top.

Something else you might consider for a street car: GoodPart's triple Stromberg manifold.

http://www.goodparts.com/shop/index.php?categoryID=2

I put that setup on a TR6 several years ago and was really happy with it. Nice and driveable with a noticeable power increase.

AndreGT6
AndreGT6 Dork
12/21/11 8:34 p.m.

Ditto.

Dual SU HS6 1.75"

Also running the MJLJ setup as well.

tvrvixen
tvrvixen New Reader
12/21/11 8:44 p.m.

I am looking at Megasquirt, wouldn't mind seeing an article about installing it on an old english car.

This guy has done it well it appears. http://www.teglerizer.com/fi/GT6_manifold/ms_gt6_manifold.html

JoeTR6
JoeTR6 Reader
12/21/11 8:58 p.m.

I would agree that Webers are overkill if you don't modify everything else to let the engine need that much fuel and air. We've run DCOE 40 Webers on a TR6 autocross car with head work, high-lift cam, tubular exhaust, electric fuel pump and an Electromotive ignition. There was definitely no flat spot in the acceleration. It was running a bit rich under full throttle, but was otherwise fine for street driving. As others have said, definitely not a bolt-on affair. There are many jet combinations in use, and yours would depend on what else is done to the engine/exhaust.

It sounds like you would be better off with the Richard Good triple Stromburg/SU intake or similar. That, a good street cam and header would be plenty of power for the street.

vazbmw
vazbmw Reader
12/21/11 11:02 p.m.

Now looking back through my emotional memory bank, I would do what Hess states. I remember saying I would never do carbs again. EFI is much easier and less time consuming + it doesn't just decide to act differently because the air temp and humidity changed by 1 point. I remember putting the car on the dyno and loosing 15hp by going just a few points too rich. If the carbs are spot on they produce serious power/efficiency...but off a bit and they hurt performance. EFI = computers are your friend. Let the computer figure it out day to day tuning.

Dr. Hess wrote: 3 DCOE's: $1500 (last I looked). Guess wrong the first time out and you have to buy 6 choke tubes, 6 emulsion tubes, 6 ... for each try. Now, if you have a BIG checkbook and really like the cool look, go for it. If you want better driveability and a wow factor, find 6 throttle bodies somewhere off something, like 1.5ea 4AGE 20v's or something, and megasquirt the thing.
amg_rx7
amg_rx7 HalfDork
12/22/11 2:15 a.m.

Megasquirt sounds like a cool option

Dr. Hess
Dr. Hess SuperDork
12/22/11 6:28 a.m.

I would not be the least bit surprised to find that these: just almost bolted up to a DCOE manifold. (4age 20v TB's)

Another option is a Suzi GSX throttle body set. They seem cheap.

Curmudgeon
Curmudgeon SuperDork
12/22/11 8:03 a.m.

Megasquirt is pretty simple to do, I'm currently putting together a list of the stuff I will need to MS the 907 Lotus in my Jensen Healey and I am seriously considering MicroSquirt for my XS650 Yamaha.

The easiest way to MS your GT6 would be to get a pair of the TBs similar to what Dr Hess posted with injector bosses made into them. That way you would have only 2 injectors. That will certainly get the job done but you wind up with varying mixtures between the cylinders due to differences in intake runner length and shape. Me, I'd weld some bungs into the stock Stromberg intake (that way you wind up with 6 injectors) then replace the 'Bergs with throttle bodies as air doors. That's the hardest part, after that's done it's mostly locating and installing the various sensors and plumbing up the high pressure fuel lines.

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