power piston
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Instructor
Joined: Nov 2012
Posts: 124
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power piston
Is anyone familiar with tuning the power piston with a rod on the bottom by adjusting the screw in the base plate? I've read that for this to work correctly you must open the plugged air bleed holes. My questions are, are they the holes next to the primary rods or the ones at the back of the bowl ? How do you open them without damaging anything?
Any info is appreciated.
Fred
Any info is appreciated.
Fred
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From: Corsicana, Tx
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All you're changing is the height of the metering rods when there is high vacuum and they are held down in the jets.
A little goes a LONG way on that setting. Don't get crazy with it.
JIM
A little goes a LONG way on that setting. Don't get crazy with it.
JIM
Pro
Joined: Nov 2008
Posts: 680
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From: Denham Springs LA
I didn't think the 71 carb had the adjustable power piston. I could easily be wrong, but I thought early carbs were not adjustable, then somewhere in mid 70's they added the adjustment capability. I remember reading a paper by Lar's that showed how to adjust/set it. I would email him and ask for that paper.
There are also two lengths of metering rods for the primaries. Maybe you have the wrong ones. I am in the middle of working on the qjet for my 71. The metering rods for the 71 qjet are 2.47" long.
Be careful, when I bought my car someone had replaced the original carb with one from a late model Pontiac, so nothing was correct. I found the correct carb and am now going through it.
Why do you need to adjust the metering rods?
I believe all you can do with the 71 qjet power piston is change the spring that's below it. With the engine running you can stick a small screwdriver down the float bowl vent tube and see if its all the way down. If you have too strong of a spring, the vacuum can't pull the power piston all the way down.
Roger
There are also two lengths of metering rods for the primaries. Maybe you have the wrong ones. I am in the middle of working on the qjet for my 71. The metering rods for the 71 qjet are 2.47" long.
Be careful, when I bought my car someone had replaced the original carb with one from a late model Pontiac, so nothing was correct. I found the correct carb and am now going through it.
Why do you need to adjust the metering rods?
I believe all you can do with the 71 qjet power piston is change the spring that's below it. With the engine running you can stick a small screwdriver down the float bowl vent tube and see if its all the way down. If you have too strong of a spring, the vacuum can't pull the power piston all the way down.
Roger
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From: charlotte north carolina
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