Running without PCV Valve - Team Camaro Tech
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post #1 of 7 (permalink) Old Jan 14th, 19, 04:34 AM Thread Starter
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Running without PCV Valve

Just curious to what would happen if I added a PCV valve to my 1966 vintage 327? Currently, I have the breather from the back of the block, plumbed with a rubber hose to the front of my Carter (late 80's vintage) AFB's PCV port and have been running the car/engine this way for over 25k miles, with zero issues. If I were to add an inline PCV valve, what benefit(s) would I gain? Engine is not stock, it has the solid scripted valve covers and the late 80's GM recast of the LT1 Z28 high-rise aluminum intake (with oil filler tube). Oiler filler tube I am running has no hose provisions and it is the twist cap design, unlike the vented push on cap type.

I have had zero issues with the above set-up, but after learning about inline PCV valves yesterday, I am wondering what gain I would see? And then would I have to also reset my fuel mixture screws by adding an inline valve?
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post #2 of 7 (permalink) Old Jan 14th, 19, 06:30 AM
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Re: Running without PCV Valve

No gain other than reduced emissions at tailpipe.
But need a vented cap on fill tube allowing air in for the vacuum applied.

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post #3 of 7 (permalink) Old Jan 14th, 19, 06:41 AM
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Re: Running without PCV Valve

Purpose of a PCV is to prevent your crankcase from exploding if there is ever a back fire through the carb. It has no effect upon power what so ever. Sucking oil fumes out of the crank case does have an effect upon your gasoline's octane rating however as it lowers the value. But the valve itself is just a safety feature.

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post #4 of 7 (permalink) Old Jan 14th, 19, 06:44 AM
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Re: Running without PCV Valve

FWIW my 67 327 came as a 2 brl (Rochester) that had a inline PCV valve between the carb and the rubber hose coming off the rear PCV port back of block.

I used a inline PCV when I swapped to a 4 brl. (hose runs to front of carb)

My oil fill tube on my intake has a breather cap and my VC are the solid stock ones
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post #5 of 7 (permalink) Old Jan 14th, 19, 08:08 AM
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Re: Running without PCV Valve

PCV stands for positive crankcase ventilation. Early engines had the vented fill cap and a tube at the back running down the bell housing called a road draft tube. When the car was in motion the draft under the car drew air out of the crankcase. Later carb vacuum drew the air through with a PCV valve. If you look at the early engines they tended to sludge up pretty bad and some think it was poor ventilation and dirt entering the fill cap screen. I like the closed fill tube with the PCV hose fitting to the carb and the rear fitting with the hose to the air cleaner to keep dirt out of the incoming air. Performance engines that likely don,t rack up a lot of road miles just use breathers to vent the pressure inside the engine usually in the valve covers.
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post #6 of 7 (permalink) Old Jan 14th, 19, 02:08 PM
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Re: Running without PCV Valve

To answer the last part of your question... I was in "road-draft" mode for a while. When i added PCV to mine, it did create the effect of a slight vac leak so yes, you do need to readjust your carb a bit for best idle characteristics. I run LT1 valve covers with a vent on one and the PCV valve on the other.

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327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.

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post #7 of 7 (permalink) Old Jan 14th, 19, 03:17 PM Thread Starter
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Re: Running without PCV Valve

I think I will just leave it as it has run just fine since I built the engine in 1991. If there was a detrimental issue with not running one (and I would think I would see something after 25,000 miles), then I would probably be more concerned.....but it doen't hurt to ask.

thanks all......
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