weber balancing
06-11-2008, 04:14 PM
#16
Racer
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Location: denmark
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sounds like it went brilliantly doug. nice one.
pete i've had a few problems with my car recently that i've sorted or am trying to sort step by step, (including replacing the fuel lines today)
so i'm gonna do my carb balance very soon and am gonna strip and clean the carbs beforehand.
my question is - how do i know if i have 40 or 46ida webers? (so i can buy the right kit...)...
http://www.automotion.com/productpag...=22&pid=110737
they are original for the car a US 69T if that helps?
(i'm an hour away from the porsche so i can't look at the facia of the weber right now...and i forgot to while i was there! doh!)
pete i've had a few problems with my car recently that i've sorted or am trying to sort step by step, (including replacing the fuel lines today)
so i'm gonna do my carb balance very soon and am gonna strip and clean the carbs beforehand.
my question is - how do i know if i have 40 or 46ida webers? (so i can buy the right kit...)...
http://www.automotion.com/productpag...=22&pid=110737
they are original for the car a US 69T if that helps?
(i'm an hour away from the porsche so i can't look at the facia of the weber right now...and i forgot to while i was there! doh!)
06-11-2008, 11:52 PM
#19
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Join Date: Apr 2005
Location: RIO RANCHO, NEW MEXICO
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Doug, C4 Pazzo,
In your post #15 you asked:
"I did notice that some of the other four cylinders did not cause the engine to labor as markedly as others when turned in. While all now do cause a response, it just seems that some respond more gradually, while others respond more abruptly. Is that normal?"
I have learned to set up the butterflies before installing the carburetors. That is, look at the bottom of the carbs to verify all butterflies are equally closed. Back the idle speed screw completely off the stop. Check that each butterfly, all three, are fully closed. Hold the carbs up to a light. It is common for a butterfly to be slightly open when compared to the adjacent butterflies. You can reset the shaft coupling or reset the butterfly in the carb bore.
The issue here is if one butterfly is not the same as the adjacent butterflies, it is necessary to set the mixture and air correction screws significantly different.
Small differences can be corrected with the screws, larger differences can be a problem.
If the idle speed stop screw holds the butterflies too far open, the lowest transition port comes into play, taking control away from the idle fuel mixture screw and the idle air correction screw.
Personally, when setting up the idle and balance I start with the idle speed screw completely backed off. This combined with butterflies that are all fully closed, gives the idle control to the idle fuel mixture screw and the idle air correction screw.
Note: even fully closed the butterflies leak air. This is by design.
You just don't want one or more open while others are fully closed.
The biggest issue I see is the idle speed stop screw is holding the butterflies open so far, the idle fuel and idle air screws are over ridden. At this point air and fuel is being supplied by the transition port and past the butterflies.
If you can close the idle fuel mixture screw and that cylinder continues to fire, the fuel is coming from someplace other than the idle port.
Same for the idle air correction screws.
In your post #15 you asked:
"I did notice that some of the other four cylinders did not cause the engine to labor as markedly as others when turned in. While all now do cause a response, it just seems that some respond more gradually, while others respond more abruptly. Is that normal?"
I have learned to set up the butterflies before installing the carburetors. That is, look at the bottom of the carbs to verify all butterflies are equally closed. Back the idle speed screw completely off the stop. Check that each butterfly, all three, are fully closed. Hold the carbs up to a light. It is common for a butterfly to be slightly open when compared to the adjacent butterflies. You can reset the shaft coupling or reset the butterfly in the carb bore.
The issue here is if one butterfly is not the same as the adjacent butterflies, it is necessary to set the mixture and air correction screws significantly different.
Small differences can be corrected with the screws, larger differences can be a problem.
If the idle speed stop screw holds the butterflies too far open, the lowest transition port comes into play, taking control away from the idle fuel mixture screw and the idle air correction screw.
Personally, when setting up the idle and balance I start with the idle speed screw completely backed off. This combined with butterflies that are all fully closed, gives the idle control to the idle fuel mixture screw and the idle air correction screw.
Note: even fully closed the butterflies leak air. This is by design.
You just don't want one or more open while others are fully closed.
The biggest issue I see is the idle speed stop screw is holding the butterflies open so far, the idle fuel and idle air screws are over ridden. At this point air and fuel is being supplied by the transition port and past the butterflies.
If you can close the idle fuel mixture screw and that cylinder continues to fire, the fuel is coming from someplace other than the idle port.
Same for the idle air correction screws.
