PVC woes
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From: S.C.
PVC woes
I have a 74 302 CID; do anyone have a schematic of how the PVC hoses are attached; currently mine is attached to a hose on the back of the card the suction makes the PVC rattle. Previously it was attached to a hose at the adapter plate on the carb is there less suction there or maybe my PVC valve is defected I just brought it ltwo weeks ago.
Jaye
Jaye
Senior User
Joined: Jan 2003
Posts: 369
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From: Rochester, NY, USA
Hi Jaye,
I apologize if I'm giving the wrong info here, but I don't think you need a PCV valve on your motor. I'm pretty sure most guys with non EFI motors just use one of the pretty stick in filters in their valve covers. I'm not bright enough to really understand what a PCV valve does, but I was not aware that carb motors needed them or even came with them.
The acronym alone means "Positive Crankcase Ventilation" which would lead me to believe that it lets air out but not in. What this buys you....I don't know.
Sorry I couldn't help more. - Brad
I apologize if I'm giving the wrong info here, but I don't think you need a PCV valve on your motor. I'm pretty sure most guys with non EFI motors just use one of the pretty stick in filters in their valve covers. I'm not bright enough to really understand what a PCV valve does, but I was not aware that carb motors needed them or even came with them.
The acronym alone means "Positive Crankcase Ventilation" which would lead me to believe that it lets air out but not in. What this buys you....I don't know.
Sorry I couldn't help more. - Brad
Lead Driver
Joined: Aug 2002
Posts: 6,682
Likes: 12
From: Saskatoon SK Canada
You need the PCV system as it helps keep the engine clean. On one valve cover there should be a breather or a hose going to the aircleaner. On the other cover should be a PCV valve that has a hose going to the carb or to a vacumn fitting on the intake manifold.
Roast em' if you got 'em
Joined: Mar 2005
Posts: 22,017
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From: Rio Rancho, NM
The PCV system was the very first emissions item and was started in the 70's. It basically takes oil vapors and runs them back through the engine. Before the PCV system engines had a "road tube" which was basically a open tube approx 1" in daimeter that exited towards the bottom of the engine. It was a oily, smoky, mess.
The PCV is basically a 1-way check valve and is usually connected to the base of the carb. All engines need it. If you dont have a way for the vapors within the crankcase to exit they will find a way (blown seals, pushed out dipstick tube, etc)
The filter on the valve cover would do the trick.
When I was a teenager I installed a really cool set of finned aluminum valve covers on my 67 Charger small block. I didn't realise at the time that there was no provision for a PCV valve or even a breather. After a few miles the engien would be covered in oil and the dipstick would be halfway out fo the tube. It tokk several times of this to realise what was happening. I ended up using breather style filler caps on that one instead of drilling my cool valve covers for a PCV.
I don't know why the PCV would be rattling. does it rattle at all RPMs or just at idle? How does the engine run? do you have a wild cam? Try another PCV valve in it (heck, they are cheap)
Good luck
Bobby
The PCV is basically a 1-way check valve and is usually connected to the base of the carb. All engines need it. If you dont have a way for the vapors within the crankcase to exit they will find a way (blown seals, pushed out dipstick tube, etc)
The filter on the valve cover would do the trick.
When I was a teenager I installed a really cool set of finned aluminum valve covers on my 67 Charger small block. I didn't realise at the time that there was no provision for a PCV valve or even a breather. After a few miles the engien would be covered in oil and the dipstick would be halfway out fo the tube. It tokk several times of this to realise what was happening. I ended up using breather style filler caps on that one instead of drilling my cool valve covers for a PCV.
I don't know why the PCV would be rattling. does it rattle at all RPMs or just at idle? How does the engine run? do you have a wild cam? Try another PCV valve in it (heck, they are cheap)
Good luck
Bobby
Fleet Mechanic
Joined: Apr 2004
Posts: 1,443
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From: Willamette Valley, Oregon
I have a 71 302, it does have a PCV valve. One valve cover has the pcv valve, runs the the block under the carb, the other valve cover has a "filter" as an inlet. I'd replace it just to rule out a bad unit, they are pretty cheap. They all rettle if you shake them (right?) it is vibrating badly?
Logistics Pro
Joined: Oct 2002
Posts: 4,489
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From: Valley Center, CA
It sounds like the engine needs a way for the air to get into the crankcase. If you just have a pcv hooked up to the carb, then you are only half way there. With a clean filter on the other valve cover, air will flow into it, through the crankcase, and out the other valve cover. With this continuous flow of air there should not be any rattling of the ball in the pcv. If that's the way you are set up already, then try reattaching the vacuum hose where it was before. Maybe you don't have a good steady vacuum where it is currently attached. 
Good luck, Jag
Good luck, Jag
