The PCV valve is rattling on my 1965 Olds 330. I just finished putting on a Pypes exhaust system with an X-pipe, Turbo mufflers, and over the axle to the bumper tail pipes. While listening to the car's new exhaust note in the driveway (it sounds awesome for a little 330/315 HP Olds!) I can hear a quiet constant ticking, like a sewing machine. It's not as loud as a lifter tick or exhaust leak.

The noise is coming from the PCV valve. It's cycling open and closed real fast. If I pinch closed the 3/8" line going from the PCV to the large fitting at the base of the carb, the noise stops. I am guessing I don't have the correct PCV valve for my modified engine. PCV valves have different spring tensions or vacuum ratings for specific applications. So how do you chose a PCV valve that will match your engine? Are they based on engine vacuum at idle? I'm getting 16" of vacuum at idle.

I am using a set of the "Oldsmobile" script (REAL TALL) valve covers, I have baffles mounted below the openings for the PCV in the passenger side valve cover and the valve cover breather in the drivers side.

Have any of you experienced a noisy PCV valve like that? Any suggestions as to what part numbers are worth a try? Do you think I need a valve with more tension so it will take more to pull it open, or one with less so it will stay open and not chatter? Which way is the right way to go? Is the PCV supposed to be pulled open at idle and closes as vacuum drops?

 

My 98 blazer does this after I put a new PCV valve in, same part number and all, just new. My 70 442 does this every once and a blue moon. Interested what others have to say.

 

That's what PCV valves do.

- Eric

 

Well, they're supposed to rattle if you are shaking it to test it...they're not supposed to be rattling real fast at idle.

At any rate, it was just a vacuum leak from the little black plastic 90 degree fitting that snaps onto the top of the PCV valve. I only had it on there because it looks better than having the hose stick straight up from the valve cover. I must of snapped it on and off too many times and it was a little sloppy. When I would push down on it the rattling stopped, so I just took it off and hooked the hose right to the nipple on the PCV valve. Its not rattling anymore, it appears to be working just like it should. When I pinch off the hose, I can hear the "check valve" or what ever is inside of it, drop off its seat.

 

Great!

Personally, I've had ones that just did that sometimes, and I never thought twice about it. Glad you got it to stop, though.

- Eric

 

I had a defective new PCV valve that was excessively noisy. I replaced it and broblem was gone.
I also had one with an original hose, which had turned very spongy, and caused a similar issue. Changed the hose and all was great.
Luckily these are cheap easy fixes.

 

PCV valves actually close in the WOT position as vacuum drops to near zero. (not enough vacuum to hold the poppet valve up) This effectively closes off any blow-by from entering the intake charge. At anything less than WOT the engine vacuum will pull on the poppet valve and allow blow-by gases to circulate back into the intake charge.
This helps keep your oil cleaner by eliminating the nasty stuff that would eventually fall out of the gases and contaminate your oil. (acids, unburnt hydrocarbons, etc.) In addition condensation is pulled into the intake charge also further helping to keep the inside of the engine cleaner.

 

Well explained Trip.