A mechanic ran the pcv to the external bowl vent

[383man]

Rumblefish360 is right. You want that vent open at idle and it closes when you step on the gas. Its part of what they call a balanced carb that vents to atmosphere at idle and on the gas it vents thru the carb airhorn so the fuel in the carb bowl has the same balanced venting that the carb airhorn does. Also if its open at idle it will also let fuel fumes out on hot days and help keep the carb from flooding. The bowl vent it not new or only on evap emission cars as the old carbs had them also and they were open to atmosphere at idle. When the closed evap system came around they would keep the fumes from escaping into the air as it vented to a charcoal canister where it held the fumes until the eng purged them out and burnt them. Or on one year around 70 to 71 they vented the bowl vent to the crankcase and then when the eng starts the PCV system pulls the fumes in the eng and burns them. Ron

 

[66chargerpat]

I'm sorry 383man and rumblefish360,I thought the CS series carter carbs. didn't have a mechanical valve on the bowl like a factory carb. If it does,it still need to be filtered. It will drawing air and crap on cooling down.

 

[rumblefish360]

No... It... Will ...not

 

[Meep-Meep]

I'm saying that external vent should be capped. AFB's have bowl vents in the air horn that vent inside the air cleaner. That external vent is for a charcoal canister and not all cabs had it. The 60's AVS and AFB didn't have them.

 

[Mr Belvedere 30144]

I had the exact same problem with the oil pan gasket leak. I could not figure this out until I changed valve covers. I looked at the breather I had on the drivers side cover. It was a cheap one with white foam inside. I could not blow or suck any air through it at all! It was like a cap. I got a new one and tested it. I could pass air through it easy. So on with the new covers. PCV on one side and breather cap on the other and wala no oil pan leak any more. Lesson learned that crank case venting and pressure control is very important on these engines!

 

[WileE]

That vent tube IS the vent, and exactly why it should NOT be capped.

 

[nm9stheham]

^^^ LOL I favor the 'speakers in the engine bay' theory!

Nope, no mercy for a mechanic who gets PAID to do things right, regardless.

 

[383man]

I'm saying that external vent should be capped. AFB's have bowl vents in the air horn that vent inside the air cleaner. That external vent is for a charcoal canister and not all cabs had it. The 60's AVS and AFB didn't have them.

Yes many carbs had external vents in the 60's that as I said before they vent to normal atmosphere pressure at idle. All carbs also have the air horn vent which off idle the carb vents thru the airhorn vent to have the same pressure on the fuel in the bowl that is in the carb airhorn. Thats why its called a balanced vented carb. Many older carbs have the external vent that alot of people did not even know it was there or did not know what it was. All they did when emmision standards got tough was put a nipple and hose on it so the fumes dont vent out in the air and are trapped in the charcoal canister. Many old Holleys have it as it is just a small rubber grommet that hooks to a rod that lifts the grommet at idle and opens a hole to the carb bowl. When you step on the gas the rod drops the rubber grommet to plug the external vent and use the airhorn vent. You dont want it capped at idlle as it also helps relief fuel vapors that are worse on todays pump gas and help keep the carb from getting to rich at idle since it will let the fumes out and not push fuel out into the airhorn. Ron

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Here is a pic of an old Holley with the external bowl vent that just vents to outside air past the little black rubber grommet at idle only. Off idle the rod drops the grommet to seal the external vent until it comes back to idle. Ron