Re: Center six pack with no bowl vent
[Re: fastmark]
#2739620
02/04/20 12:35 PM
02/04/20 12:35 PM
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Joined: Aug 2003
Posts: 43,308 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,308
Bend,OR USA
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Not all Holley two barrel carbs had smog related vents from the fuel bowls, it still has the front vent tube behind the squirters, doesn't it? I'm wondering if the 1969 six pack carbs had the extra vent tube in them , maybe not
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Center six pack with no bowl vent
[Re: Cab_Burge]
#2739650
02/04/20 01:52 PM
02/04/20 01:52 PM
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Joined: Jan 2003
Posts: 9,436 Blair County,PA
62maxwgn
master
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master
Joined: Jan 2003
Posts: 9,436
Blair County,PA
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Two on left are A12 auto front, 70 4 spd rear,two on right are both A12 4 spd.I have found quite a few A12 without bowl vent but all were early March production,all main body casting the same,69/70.Also,most A12 center's had black bowl vent arm.On the Corvette tri-power,the 67 had no bowl vent,68/69 had vent. As to whether it would be an issue,the Holley 4 bbl dual inlet center hung front bowl came with or without a vent depending on the application.
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Re: Center six pack with no bowl vent
[Re: 62maxwgn]
#2739768
02/04/20 09:06 PM
02/04/20 09:06 PM
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Joined: Jan 2003
Posts: 6,435 Abilene, Texas
fastmark
OP
master
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OP
master
Joined: Jan 2003
Posts: 6,435
Abilene, Texas
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Thanks Bill. All of the 440 carbs I have that are 69/70 have the black rubber bowl vent. Some of the later replacements 440, 71 440 and all my 340 carbs have the vent with the hose. This may be the factory bowl on this carb. It’s an early carb. I forgot the date, but’s its earlier than my oem carb for my A12. It’s has some changes on it. The main bodies have all been milled flat and the metering block has been changed. It does have the 225 plates with the holes drilled in them like we talked about.
Last edited by fastmark; 02/09/20 10:40 PM.
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Re: Center six pack with no bowl vent
[Re: topside]
#2739875
02/05/20 09:44 AM
02/05/20 09:44 AM
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Joined: Jan 2003
Posts: 6,435 Abilene, Texas
fastmark
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Posts: 6,435
Abilene, Texas
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I'm pretty ignorant about 6-BBL/Six-Pak/6-Pack setups, but I'm wondering if bowl venting was subject to CA emissions rules ? They changed to the controlled venting into a hose sometime in 70 but they were only connected on the CA emmision cars. My AAR has it and it uses a three nipple breather.
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Re: Center six pack with no bowl vent
[Re: 6bblgt]
#2739989
02/05/20 02:18 PM
02/05/20 02:18 PM
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Joined: Jan 2003
Posts: 9,436 Blair County,PA
62maxwgn
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master
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Blair County,PA
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for 1969: all the A12 Six Pack center carburetors are 50 state WITHOUT a bowl vent
for decades the only 440+6 center carburetors available new have been the CA emission units with a bowl vent Then tell me why the set of A12 carbs I just unpacked,center 4392,dated 121 9,original carbs ,never touched since new,never been apart has bowl vent with black vent arm. I have been doing carbs since the late 80 s, I have received both sets in pieces and those that were untouched from new,like I said above (I have found quite a few A12 without bowl vent but all were early March production) .
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Re: Center six pack with no bowl vent
[Re: 62maxwgn]
#2740255
02/06/20 10:33 AM
02/06/20 10:33 AM
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Joined: Jan 2003
Posts: 6,435 Abilene, Texas
fastmark
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OP
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Posts: 6,435
Abilene, Texas
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for 1969: all the A12 Six Pack center carburetors are 50 state WITHOUT a bowl vent
for decades the only 440+6 center carburetors available new have been the CA emission units with a bowl vent Then tell me why the set of A12 carbs I just unpacked,center 4392,dated 121 9,original carbs ,never touched since new,never been apart has bowl vent with black vent arm. I have been doing carbs since the late 80 s, I have received both sets in pieces and those that were untouched from new,like I said above (I have found quite a few A12 without bowl vent but all were early March production) . I think what Dan is referring to is the WITHOUT bowl vent in his statement does not have the tube. It has the black rubber and arm in the picture. My original question was about a carb with NO HOLE OR ARM AT ALL. What you are saying, Bill, makes sense. I’ve never seen one with no hole so this must be an early set. You answered my question.
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Re: Center six pack with no bowl vent
[Re: 6bblgt]
#2740458
02/06/20 06:43 PM
02/06/20 06:43 PM
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Joined: Jan 2003
Posts: 9,436 Blair County,PA
62maxwgn
master
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master
Joined: Jan 2003
Posts: 9,436
Blair County,PA
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I saw that lever also (the carb looks a little darker from fuel staining), the float screw/nut looks different as well - but saw no flapper & figured I'd add the pics (taken pre-'90) The rear carb I pictured has the correct screw,the front is what you get now.Also,the picture of the restored engine has the wrong choke pull off,the straight nipple is 4bbl which is what you get no,the original has a 45 degree angle.
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Re: Center six pack with no bowl vent
[Re: fastmark]
#2740543
02/07/20 12:11 AM
02/07/20 12:11 AM
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Joined: Jun 2014
Posts: 1,340 VA
dragon slayer
pro stock
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pro stock
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VA
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No expert on Holley, but are we confusing types emission systems and types of vents too? CAP later CAS was the actual emission control of the exhaust. All States were CAS by 68. The Carbs both Carter and Holley that had a vent tube were for the ECS (Evaporative Control System) which was a requirement for CA only starting in 70. This was capturing vapors, both at carb, and fuel tank to burn in engine or return to tank as liquid. Having a bowl vent with rubber stop (normally open) was not part of ECS since it vented to atmosphere. Frankly, I do not know why there was a bowl vent to atmosphere that started in 67 for CA CAP/CAS. The bowl vents started showing up on Carter AFB in 67 for the CAP/CAS CA only cars. Became standard for AVS in 68 since all states were CAS. But this was only a Chrysler thing as best I can tell. Plenty of other manufacturers using Carter did not use it despite having to meet all 50 state emissions in 68 and up. Later other manufactures used the internal vent lever to the tube that went back to the ECS. Having a vent that captured vapors and routed back to tank, or burned through engine makes sense. The vent that went to atmosphere on a bowl that had other vents to inside of air cleaner doesn't make much sense to me, unless it was a pressure thing to ensure proper calibration with a dirty filter. Open with closed throttle, and closed when you accelerated to full throttle and got a pump shot. At least that is how carter carbs worked. Again a Chrysler thing mostly.
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