Weber Carb on Chevy SB

[Oliver S.]

Hello,

I'm just curious if anybody has had any experiences with Weber Carbs on Chevy SBs (I don't want to install one). As far as I know ISO used Weber on their cars equipped with Corvette engines.
I've read an ad here in Germany offering Weber for 3000$ for Chevy SB. A lot more expensive than Holley, Carter/Edelbrook.

Oliver

[Joe C.]

Re: Weber Carb on Chevy SB

Hello,

I'm just curious if anybody has had any experiences with Weber Carbs on Chevy SBs (I don't want to install one). As far as I know ISO used Weber on their cars equipped with Corvette engines.
I've read an ad here in Germany offering Weber for 3000$ for Chevy SB. A lot more expensive than Holley, Carter/Edelbrook.

Oliver

4-2bbl side drafts were used on the 377 c.i. version of the Grand Sport. The ad you refer to might be for a reproduction of that setup.

[Oliver S.]

Re: Weber Carb on Chevy SB

Is there something special in the design of the Weber compared to the normal ones?

Oliver

[Stuart F.]

Re: Weber Carb on Chevy SB

I believe there are down draft Webers as you see them on old Ferraris all the time. But whether they made them in 4 barrel versions I don't know, or even in a configuration that would mount on a typical 4 barrel manifold.

I also seem to recall, in general, Webers have very sophisticated metering systems, perhaps even with variable venturis - supposed to be as good as or better than most fuel injection systems, except perhaps those that employ individual stacks per cylinder. The F.I. systems, like the Rochester constant flow, tend to have fuel reversion which causes the fuel droplets to puddle instead of atomize with the incoming air.

Stu Fox

[Bill M.]

Re: Weber Carb on Chevy SB

Weber (4 2bbl downdrafts) were used on the Formula A SCCA single-seat racers in the 60s. The engine was based on a 302 Chevy; max. displacement was 5.0 liters. (I remember they had to run stock rods, so you bought many rods and picked the best ones to polish like a mirror.) The Webers were gorgeous. Weber had this wooden box with all the jets and adjustment pieces in it. Very neat stuff!

[Jim L.]

Re: Weber Carb on Chevy SB

I've used Weber DCOE carburetors on my vintage racer for the last nine years.



The advantage of Webers is their near-infinite tunability. With replaceable venturies ("chokes" in Weber-speak), you can size the air flow capacity to any engine. The jetting options allow you to chose the conditions under which the low speed circuits turn off and the main circuits turn on. You can tailor the fuel flow precisely at any engine RPM.

The disadvantage of Webers is that you must do all of those things. You can't just bolt'em on and go.

Webers tend to be expensive, as the OP noted. You get what you pay for; they are extremely well engineered and well made. The throttle shafts, for example, run in ball bearings, not bushings. There are no pump diaphragms to rupture at inopportune times, no power valves to blow out. Jets can be changed without draining the fuel bowls.

Once set up correctly, they work well and they are pretty good eye candy, too.

Jim

[Steven B.]

Re: Weber Carb on Chevy SB

Hello,

I'm just curious if anybody has had any experiences with Weber Carbs on Chevy SBs (I don't want to install one). As far as I know ISO used Weber on their cars equipped with Corvette engines.
I've read an ad here in Germany offering Weber for 3000$ for Chevy SB. A lot more expensive than Holley, Carter/Edelbrook.

Oliver

Hi Oliver! Iso (a refrigeration manufacturer) used sock 4 bbls on the stock 327 Chevy Iso Rivoltas and later on the stock 351 Fords. They did use Webers on the non-four-seater Grifo as an option. Webers are now manufactured in Spain. Webers come in downdraft and side draft versions, 1 bbl, 2 bbl, and 4 bbl versions. Side draft and down draft manifolds are available for Chevy engines. Years ago I watched a friend tune his Ferrari (when they were alot cheaper) with Webers and more recent helped with a Weber set-up on a Spitfire. The carbs are surprisingly easy to set-up and tune. The carbs perform very well and the design used in the design of some current 4 bbls. $3,000.00 if inclusive of carbs, manifold and linkage isn't bad---used?

Steve

[Steven B.]

Re: Weber Carb on Chevy SB

I've used Weber DCOE carburetors on my vintage racer for the last nine years.



The advantage of Webers is their near-infinite tunability. With replaceable venturies ("chokes" in Weber-speak), you can size the air flow capacity to any engine. The jetting options allow you to chose the conditions under which the low speed circuits turn off and the main circuits turn on. You can tailor the fuel flow precisely at any engine RPM.

The disadvantage of Webers is that you must do all of those things. You can't just bolt'em on and go.

Webers tend to be expensive, as the OP noted. You get what you pay for; they are extremely well engineered and well made. The throttle shafts, for example, run in ball bearings, not bushings. There are no pump diaphragms to rupture at inopportune times, no power valves to blow out. Jets can be changed without draining the fuel bowls.

Once set up correctly, they work well and they are pretty good eye candy, too.

Jim

Jim, beautiful set-up! Very sanitary Corvette. 'More pics???

Steve

[Mike G.]

Jim, what is that disc-shaped gizmo

with the ribs, tucked just aft of the LH fender liner, and what's the access door on the fender for?

[Jim L.]

Re: Jim, what is that disc-shaped gizmo

with the ribs, tucked just aft of the LH fender liner, and what's the access door on the fender for?

The ribbed gizmo is the power brake booster, mounted on a 90 degree offset bracket for Weber clearance. The access door leads to the master cylinder.


Steve asked for more pictures. Here's a link to a moving picture (a talkie, even....):

http://www.youtube.com/watch?v=7Mfw7Jjd97s

Jim

[Steven B.]

Re: Jim, what is that disc-shaped gizmo

The ribbed gizmo is the power brake booster, mounted on a 90 degree offset bracket for Weber clearance. The access door leads to the master cylinder.


Steve asked for more pictures. Here's a link to a moving picture (a talkie, even....):

http://www.youtube.com/watch?v=7Mfw7Jjd97s

Jim

Great video---and sound Jim! I like the hood catching a little air .

Steve

[Jim L.]

Re: Jim, what is that disc-shaped gizmo

Great video---and sound Jim! I like the hood catching a little air .

Steve

Thanks, Steve. The hood catches a LOT of air, actually. I keep it loosely tied at the rear to relieve pressure that builds up underneath. It pops up at approximately 100 MPH air speed over the vehicle.

Regards,
Jim

[Stuart F.]

Re: Weber Carb on Chevy SB

Jim;

Thanks for the video - a great experience. It sounds like you were just loafing, although that's not the case. What redline do you impose on yourself?

Thanks too for the weber explanation. I never had any experience with them, only read about them over the years. They sure do look impressive.

Stu Fox

[Jim L.]

Re: Weber Carb on Chevy SB

Jim;

Thanks for the video - a great experience. It sounds like you were just loafing, although that's not the case. What redline do you impose on yourself?

I'm glad you enjoyed it. The tiny keyhole window youtube gives you completely masks the real-life experience, so you miss a lot.

That particular video was a 7/10s practice session in which I was giving a demonstration ride to our crew chief, the fellow visible at the beginning who starts the car. If you pick a reference point and time the lap, you'll get a time that's about 10 seconds slower than full racing speed.

Redline was around 5500. It wasn't a race; no sense killing the engine. In competition, I go by start finish with the engine turning around 6200 and the speedometer (yes, it's connected) indicating ~135. Looks to me like the speedo was indicating around 120-125 at start/finish that day.

Thanks too for the weber explanation. I never had any experience with them, only read about them over the years. They sure do look impressive.

To provide some actual Weber content to this posting:

For each venturi, there are seven replaceable, calibrated parts:

1. The venturi itself (aka "choke") -- the size of this in proportion to the throttle bore determines how much of a vacuum signal is available to the main circuit.

2. The auxilliary venturi where fuel discharge happens -- This, too, can be tweaked to influence main circuit turn on.

3. The idle or low speed jet - Two jets in one. The fuel orifice determines the low speed fuel flow. The air orifice determins when the low speed circuit turns off.

4. The main jet -- Determines fuel flow once the main circuits turn on.

5. The emulsion tube -- Is a factor in determining when the mains are active and has other properties that I don't fully understand.

6. The air corrector jet -- Limits the fuel flow at the high end of the RPM range

7. The pump jet -- Accelerator pump discharge port and an auxilliary fuel port during WOT operation

For all of these there are multiple options which, if you multiply them all out, result in hundreds if not thousands of jetting combinations. An engine or chassis dyno is virtually mandatory if you are trying to get a set of Webers dialed in.

Jim

[Joe C.]

Re: Weber Carb on Chevy SB

Jim,

Great video!!!!!!
Is the DeWitt's painted silver? How much diff did it make as far as heat rejection capacity.

Joe