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Author Topic: 69Z air fuel mixture  (Read 1467 times)
sixt9x33rs
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« on: March 28, 2010, 07:16:54 PM »

I tuned my carb today on my Z and the passengers side air fuel screw is about 1.75 turns off the seat. Which I understand is within normal range. However, the driver's side air fuel screw is only off the seat about .75 turns. My car with this tuning generated 14 inches of vacuum at about 1200 RPM. After the tune I took the car out and it clearly runs well.

Do I need to be concerned that the driver's side screw is only .75 turns off the seat?

Thanks,
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'69 RS Z/28 Olympic Gold, 711
Flat hood no spoiler, black top, endura, 4:10
POP 39,000
69 X77 Z/28 69 711 Original Paint Unrestored
'69 X66 Convertible Cortez Silver 712 black top Endura, auto, bumper guards, am/fm rear speaker 44k miles
flyingskibiker
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« Reply #1 on: March 29, 2010, 01:32:53 AM »

I wonder if you could turn one in a 1/4 and one out a 1/4 to make them even and get the same results.?.?  I assume it was tuned to best vacuum?
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JohnZ
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« Reply #2 on: March 29, 2010, 09:31:05 AM »

I tuned my carb today on my Z and the passengers side air fuel screw is about 1.75 turns off the seat. Which I understand is within normal range. However, the driver's side air fuel screw is only off the seat about .75 turns. My car with this tuning generated 14 inches of vacuum at about 1200 RPM. After the tune I took the car out and it clearly runs well.

Do I need to be concerned that the driver's side screw is only .75 turns off the seat?

Thanks,

Don't worry about "turns" - adjust the idle mixture screws for highest steady vacuum at normal idle rpm (usually 900-1000 rpm with a "30-30" cam); I usually see 9"-10" Hg. at that rpm.
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'69 Z/28
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Stingr69
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« Reply #3 on: March 29, 2010, 10:01:03 AM »

That used to happen with my 650 DP until I bought a wideband O2 sensor and set the carb up with it. Starting with the baseline butterfly setting on the RPM screw position and tuning with the mixture screws had them both in the right place. I moved on to do the main jets to adjust the cruise mix and verified the secondary jetting at WOT. The car runs real nice and much less gasoline smells now. I think your screws might be telling you something else is wrong.

-Mark.
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sixt9x33rs
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« Reply #4 on: April 03, 2010, 08:20:45 PM »

I tuned my carb today on my Z and the passengers side air fuel screw is about 1.75 turns off the seat. Which I understand is within normal range. However, the driver's side air fuel screw is only off the seat about .75 turns. My car with this tuning generated 14 inches of vacuum at about 1200 RPM. After the tune I took the car out and it clearly runs well.

Do I need to be concerned that the driver's side screw is only .75 turns off the seat?

John when I started the tuning I was idling at 900 and the air fuel mixture was so badly off when I finished I had gotten the rpm to 1200. I was adjusting to highest vacuum.

Thanks,

Thanks,

Don't worry about "turns" - adjust the idle mixture screws for highest steady vacuum at normal idle rpm (usually 900-1000 rpm with a "30-30" cam); I usually see 9"-10" Hg. at that rpm.
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'69 RS Z/28 Olympic Gold, 711
Flat hood no spoiler, black top, endura, 4:10
POP 39,000
69 X77 Z/28 69 711 Original Paint Unrestored
'69 X66 Convertible Cortez Silver 712 black top Endura, auto, bumper guards, am/fm rear speaker 44k miles
GaryL
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« Reply #5 on: June 14, 2010, 10:09:41 PM »

I tuned my carb today on my Z and the passengers side air fuel screw is about 1.75 turns off the seat. Which I understand is within normal range. However, the driver's side air fuel screw is only off the seat about .75 turns. My car with this tuning generated 14 inches of vacuum at about 1200 RPM. After the tune I took the car out and it clearly runs well.

Do I need to be concerned that the driver's side screw is only .75 turns off the seat?

Thanks,

My DZ carb has both screws out at least 1.5 turns or more. I can not get a rich smell at idle. I think I need Eric to adjust the idle feed restrictors in the replacement metering block in my carb.
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Gary

Lemans Blue X33. DZ, M20, manual steering. Only BU code rear end is original.
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