Progressive Throttle Linkage ???'s

[Dan the Man]

How many of you are running twin carbs and using a progressive throttle linkage?
What are the pros and cons of them?
Did you do it for performance issues or fuel economy?
Did you notice any difference in fuel economy?

I'm asking because it has been suggested I switch to a progressive linkage. Right now I am burning a ton of fuel and getting very little mileage out of it. I have a small block Chevy with a mild cam and a tunnel ram with dual 500 cfm carbs. At best guess, I'm getting about 9-10 mpg. Note: TH350 trans with 2.45 gears in rear end.

 

[409T]

Progressive linkage helps. I usually expect somewhere between 10 - 12 mpg with two 4's and a tunnel ram but I know there are other people doing better.

 

[Spanky]

Are those 500 cfm carbs two barrels? If so, that might explain poor mileage, since with four-barrels you typically only use the 'small' primary side around town.

 

[fletcherson]

I ran progressive linkage on a tri power with good results. On mine, you could stage the primary carb to run until about half throttle then the secondary carbs came in. Could stage both secondary carbs as dump carbs or stagger them. Staggering them seemed to allow a smoother transition to full throttle without the stumble or whatever, it depends on how fast the petal dropped. Running on one carb for basic cruising definitely helped on fuel mileage and keeping the plugs cleaner.

 

[Island Girl]

Successfully going from a dual setup to a single on a tunnel ram style manifold is pretty much dependent on the way the manifold is made.

Some were made with rather large plenums under the carbs and had interchangeable tops to accommodate both dual and single carb setups.

Most, however, had rather small plenums, (or almost none at all) . . . where the carb mounts were designed for square bores and each runner was almost right under the associated bore.

If you tried to run a small plenum tunnel ram with a single carb, you'd be at serious risk of having some cylinders running wayyyy too lean and causing serious damage.

If you want to stay with the look of the tunnel and go to a single carb, be sure to find one with the interchangeable tops.

 

[409T]

I've tried a number of them, for me this worked the best Real Street Ram

 

[benT]

Both my '27 and my dads run dual quad intakes with Edelbrock 500's with the edelbrock progressive linkage. The progressive linkage works great and they both ron good for being mild small blocks. Most of the time the car runs on the back carb, but when you get on it the front carb kicks in. I recommend the setup.

 

[PotvinGuy]

Dan...which carbs are you using? Make and model.

 

[Oban Ron]

I ran a progressive linkage with two Edelbrock 4- barrel 500 cfm's and a Weiand 6-71 on a 350 small block. I found that cruising around town was nice with just the rear carb, but after a while I realized I was getting a light spray of fuel on my windshield when I stomped on it. After rebuilding the carb and making a number of adjustments I realized that the fuel was pooling in the unused carb, and when I activated it a light amount of fuel leaked and sprayed along side of the piston. I switched to direct linkage where I am using both now. All is good. I don't drive it that much so the loss of gas mileage doesn't bother me much, not to mention when I step on it, it jumps right from the get go.

 

[HenrysT]

You could try and adjust the front carb blades so it has just a crack open so it won't pool.