Author Topic: will a pcv valve cause a lean condition?  (Read 71 times)

Offline bruno

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will a pcv valve cause a lean condition?
« on: March 23, 2026, 02:42:06 PM »
long story short, I’m having trouble with what i think is a lean bog right off idle. 68 chevelle 396, mild cam. idle vac. is 18, steady. timing is 10 initial, another 10 from manifold VA, centrifugal starts at 950ish, adding another 26 at 3600ish. it idles well, both mixture screws have response, they’re set at 3 turns out. accelerator pump has a good shot in both primaries. idle tubes are .037, DCR is 052, LIAB is 063, UIAB is 070. holes under i’ll screws are 085. I think i should have lots of idle fuel. when i pull th pcv valve and block it off, the rpms drop about 50, and the bog nearly disappears. should the pcv be flowing a ton of air at idle? it is connected to manifold vacuum at the front of the base plate. I did replace this pcv a while ago from napa, so it SHOULD be the correct one. I also have an air cleaner base that has a spot for a pvc hose, would that be a better option?

Offline bruno

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Re: will a pcv valve cause a lean condition?
« Reply #1 on: March 23, 2026, 02:42:57 PM »
sorry i forgot, Idle bypass air is 095.

Offline bruno

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Re: will a pcv valve cause a lean condition?
« Reply #2 on: March 23, 2026, 06:53:13 PM »
well it seems like an adjustment to the APT cured the bog. the tip in caused a 50 rpm increase now.

Offline von

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Re: will a pcv valve cause a lean condition?
« Reply #3 on: Today at 03:50:20 AM »
A connection to the air cleaner is for clean air to the engine that the PCV valve is allowing "oil fumed air" to be sucked out.