Holley w/ Mech. Secd. 1.1 Vs. 1.6 ?

[George Snyder]

When changing from 1.6 to 1.1 on the throttle linkage does it have any effect on the carb jetting?
Thanks,
Bud

[scottj]

I have a few special ratio linkages ranging from one that only opens the secondaries 1/8 and at the very last part of the pedal travel to a standard 1:1 ratio. I am constantly switching linkages without any effect on jetting. We jokingly refer to it as the "honest man's traction control".
Scott

[Jmar]

Can you get these at a Holley parts dealer like Ramchargers or Summit? Does the new link seem to help throttle response?

[George Snyder]

Does the new link seem to help throttle response?

No it sucks! All it did was foul the plugs. I have already changed back.

I am really starting to believe that the B303 Cam just has too much overlap to be carbed effectively.

If you want to try it for yourself send me your address and i will send you mine. Save yourself $8.

Bud

[scottj]

Whether or not the 1:1 linkage will be better or not will depend on your combination.

Generally the lighter the vehicle, the lower the gearing, and the higher the power, more likely you'll benifit from the 1:1 ratio.

Since mechanical carbs are delivering fuel and air ahead of the engines torque curve, you have to properly match the delivery to how quickly the engine can use it (how quickly it can build rpm).

Vacuum secondary carbs deliver fuel and air behind the torque curve so fuel and air delivery is automatically matched to the engine's needs.

If your combination runs best (responds and builds rpm quickest) with a 1:1 mechanical carb, then a progressive ratio mechanical or a vacuum carb will "soften" throttle response and slow rpm build by comparison.

On the other hand, if your combo needs a vacuum carb, then it will run worse (poor response) with a mechanical secondary and worse yet (terrible response) with a 1:1 ratio.

In some cases with very high HP and limited traction, a progressive ratio mechanical or even a vacuum carb with its "softer" throttle response can aid in getting the car to hook up off the corner, where the 1:1 linkage will light up the tires.
Scott

[Jmar]

Thanks guys.

It sounds like I shouldn't mess with it. I'm assuming that a stock 750 carb has a 1:1 ratio.

Jeff

[scottj]

Jeff,
Re-reading my first post I see I was misleading when I refered to the 1:1 as standard. It's standard or baseline on MY carbs.

The 1:1 linkage (primaries and secondaries open simultaniously) is for special race applications. The progressive linkage is standard. It's easy to tell the difference; with the standard linkage the primaries open about 1/2 way before the secondaries come in.

Scott

[Jmar]

Scott,

Thanks for the info. I'm sure mine has a progressive rate link. I have been slowly tweaking my carb and have received mixed advice that my carb is too big for my application (750 dp), or that it's just right. I have a cam with 230I 220E @ .050, trick flow 23 degree heads, 3.55 gears, RPM manifold, street rod headers and a 2800 stall convertor. According to the holley book this looks like a good match for a 750.

When I took it to a chassis dyno shop, I ran it with a broad band O2 sensor and was told to lean it out for more power. The dyno operator was able to gain 10 hp by simply leaning out the idle circuit. So I ultimately reduced the main jets by 4 numbers in front and back. This created a part throttle (cruise) stumble and I was able to reduce this by having the power valve open at a higher manifold. It still has a small hesitiation at around 2500-2700 RPM when I open all barrels. I think it is when the back 2 start to open. Should I look into a slower opening rate for the secondaries, play with the power valve a little more or just get a smaller carb?

Thanks

Jeff