2 different holley 650's. 2 different problems. suggestions?
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Supreme Member
Joined: Mar 2001
Posts: 3,306
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From: Fl
Car: 5.3L turbo 2800lbs RWD
Engine: Prefer 3L Iron & 5.3L Aluminum
Transmission: 4l80e
Axle/Gears: 3.512
2 different holley 650's. 2 different problems. suggestions?
2 carbs at stake here. one is a 650 holley vacuum secondary.
the other is a 650 holley mechanical double pumper.
the VS carb has secondaries that will not close completelly until you play with the gas a bit. they also close slow. after i remove my foot from the gas right after WOT i can feel the car still pulling as the secondaries close. they also cause a very high idle until you press then shut.
Oh, thats not it. that carb also has a huge problem delivering fuel it seems. it worked decent, but all of the sudden, the engine started missing really bad. after replacing plugs and wires it didnt go away. finnaly for the heck of it i replaced the carb with the OTHER 650 and the problem fixed. i wonder what THATS all about?
----
THIS carb, 650 DP, is on the car right now. its problem is simple. under WOT it runs good. under cruise there is no lean hesitation. but under part throttle acceleration it wants to stumble and hesitate, if i give it a little more gas (NOT Enough to open the power valve) it clears up but runs lean until i let off, then it shows rich. (A/F guage).
It runs rich in neutral, lean in gear. it cannot be stabbed without a stumble for sure. off-idle is horrable. the pump shot seems to be at fault there, but even off idle with very very very light throttle is still has a stumble until the rpms pick up. very odd. on the highway it reads lean and the more you step on the gas the leaner it gets, until 6.5" when the PV opens then it goes back to rich. until then, it just gets leaner and leaner.
If i go up on the jets anymore it runs REALLY rich at light throttle cruise, till you step into it a little, then it goes back to lean like before. I dont want to increase jet size anymore since it seems to cruise fine the way it is, and i like fuel economy. its just the off idle performance im mainly concerned with. its even got a 50CC rear Accelerator pump.
the other is a 650 holley mechanical double pumper.
the VS carb has secondaries that will not close completelly until you play with the gas a bit. they also close slow. after i remove my foot from the gas right after WOT i can feel the car still pulling as the secondaries close. they also cause a very high idle until you press then shut.
Oh, thats not it. that carb also has a huge problem delivering fuel it seems. it worked decent, but all of the sudden, the engine started missing really bad. after replacing plugs and wires it didnt go away. finnaly for the heck of it i replaced the carb with the OTHER 650 and the problem fixed. i wonder what THATS all about?
----
THIS carb, 650 DP, is on the car right now. its problem is simple. under WOT it runs good. under cruise there is no lean hesitation. but under part throttle acceleration it wants to stumble and hesitate, if i give it a little more gas (NOT Enough to open the power valve) it clears up but runs lean until i let off, then it shows rich. (A/F guage).
It runs rich in neutral, lean in gear. it cannot be stabbed without a stumble for sure. off-idle is horrable. the pump shot seems to be at fault there, but even off idle with very very very light throttle is still has a stumble until the rpms pick up. very odd. on the highway it reads lean and the more you step on the gas the leaner it gets, until 6.5" when the PV opens then it goes back to rich. until then, it just gets leaner and leaner.
If i go up on the jets anymore it runs REALLY rich at light throttle cruise, till you step into it a little, then it goes back to lean like before. I dont want to increase jet size anymore since it seems to cruise fine the way it is, and i like fuel economy. its just the off idle performance im mainly concerned with. its even got a 50CC rear Accelerator pump.
Joined: Mar 2000
Posts: 43,187
Likes: 46
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
The VS has a binding problem, either in the throttle shaft or the diaphragm.
The DP needs a higher number power valve so it will open at a higher manifold vacuum. Right now, you have to drop the vacuum too much to get it to open, then you're too rich. So, get it to open sooner and jet down accordingly.
The DP needs a higher number power valve so it will open at a higher manifold vacuum. Right now, you have to drop the vacuum too much to get it to open, then you're too rich. So, get it to open sooner and jet down accordingly.
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