Vaccum line question...

[87AccordsterLx]

My uncle and I were looking forever for a vacuum line that we could split to plug into the pump that controls the secondary carb barrel. I am trying to get the second barrel to open with the first whenever the gas is pressed. Does this make any sense? I’m somewhat new at this... Basically I need a line that will supply vacuum as soon as the gas is pressed and increase the vacuum pressure to open the barrel up more and more as the petal is pressed further. Thanks.

[mindlos]

I've been hoping Mike was working on another secondary improvement. The only vacuum signal that increases with rpms is venturi vacuum. So the way it is normally hooked up is to the primary venturi vacuum and the problem is that it opens too damn late for my taste. If there was a way to magnify the primary venturi vacuum it would be great. Manifold vacuum works the other direction and is also determined by the amount of throttle. I really wish we can brainstorm on this one.

[A20A1]

you can open the diaphragm and change the spring to a stiffer one... but remember there is a lock on the secondary... if you look as the throttle linkages there is a nub that sticks out on the secondary shaft and rolls along part of the linkage on the primary shaft. There is a dip in the path the nub takes... and so as the dip is reached the nub no longer hits the primary linkage and the secondary linkage can move freely.


sorry for any errors... this is mostly from memory.

[mindlos]

How easy is it to take the diagphram apart without destroying it?

[A20A1]

hmm I may have thought of it the wrong way... it may need a softer spring...

I wish I still had a secondary diaphragm to mess with.

Hopefully all you need to do is pry the lip holding the cap down, and the cap will fall off.

[mindlos]

If the function of the spring is to return the diagphram when there is no vacuum then your most recent statement would be the right one coz that would mean the diagphram would be pulled at a lower vacuum signal.

Here's something I've been mulling over the last day. You could put a T-connector so that one end goes to the diagphram, one end to a one-way valve then manifold vacuum, then the last and goes to a one-way valve then the port for the secondary on the carb. The one-way valves would make sure the 2 vacuum signals do not work against each other and produce a less net signal.

As a result there would always be a vacuum pulling on the diagphram (whichever of the two is greater) and keep it open as long a the throttle position allows it to.

I already see a few problems. Firstly, the net vacuum signal would decrease as manifold vacuum decreases then increase at the point that venturi vacuum is greater than manifold vacuum. We need a steady up trend not a dipping trend. At best maybe we can limit.

Secondly, at the point that the throttle position allows the secondary to open there may still be a stumble if the secondary opens fully. So we still need to prevent the manifold vacuum from openning secondary fully unnecessarilly. Maybe it could metered to a lower value by some valve.

Thirdly, the secondary better not bind the notch on the throttle linkage when the pedal is not pressed, preventing the throttle plate from closing. Talk about a runaway car!!!!!!!!!

Fourthly, who knows what will happen when venturi vacuum = manifold vacuum??? Definitley dont wanna find out on a trial run!

I guess I could go on. If you read all this, I WAS THINKING ALOUD :D. Definitely wont work. The spring seems to be the best approach!!

[shepherd79]

i don't understand, i though i corrected the bogging down problem.
look at the How to remove vacuum lines. it should be updated.
The old how to explains how to remove the vacuum lines without losing gas mileage. Well, thanks to Mike (A20A1) you can get rid of the air correction. my car performs alot better.
So check the HOW TO section.

[mindlos]

I do remember you guys talking about eliminating the air jet correction alltogether and that helpng, including the whole leaning out problem. Since I charged up my A/C I had to go back to a vacuum secondary since I needed the flap on the manual secondary when I reinstalled the A/C load diagphram. Unless I get another flap I'm stuck with the vacuum secondary.:(

[shepherd79]

you can always get the flap from junkyard.
if you want, i can mail one to you.