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Discussion Starter #1
I am at a loss,have a ticking sound on a recently rebuildt 350,about 3000 miles. Have adjusted all the lifters several times, the motor runs quiet till we hook up the vaccum hose from PVC to bottom of carb,then starts ticking,remove the hose and is quiet again , have replaced the PCV same results.
The ticking sounds like lifters, but why does it disappear when the vaccum hose is taken off carb.?
Have had a couple of mechanics listen to it and they don't know has them stumped. Don't want to open up if we don't have to.
Does anyone have any ideas as what this maybe ?
We used break in oil for the first 750 miles,then used a good oil till 2000 miles ,then put in a Cam Oil about 600 miles later this ticking sound appeared.
 

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Maybe an exhaust leak. Put a stethascope or rubber tube to your ear and put the other end around the exhaust headers or manifold to see if you hear the ticking
 

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Since the ticking noise only happens when you hook up the PCV valve I would check several things. First be sure that you have the correct PCV valve for the engine. May not have enough vacuum to hold the valve open. Second, be sure the valve fits tightly in the grommet.
Good luck
 

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my call would be a problem with the PCV valve.
 

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Check valve covers inside for rocker contact... had a similar problem when running proform aluminum covers... the pushrod end of the rocker arm barely touched the cover when warmed up...
 

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Discussion Starter #6
Thanks for your thoughts. I just read on another site that you can get different sizes of PCV valve, never heard of this before . Do they have different flow rates ?
 

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Without question or doubt you have the wrong pcv valve. It's not wrong by much. The pintle is in there rattling up and down with the vacuum and the spring and the vacuum are fighting each other. Sometimes an idle mixture adjustment for highest vacuum will cure it. If not, you need one for an engine with slightly lower vacuum. Went through same thing on my sons Camaro.
 

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Any idea which one that would be?
I can certainly try to help you. It is trial and error unfortunately. I've never wanted to spend the big bucks on an adjustable one so I've done a lot of trial and error lol. I need some details on your engine though. Compression, what is the cam that's in there, what carb. , what can you tell me? Also what is the pcv valve you currently run? Do you know what it's supposed to be for?
 

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1968 Chevy II Nova, Central Arkansas
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I can certainly try to help you. It is trial and error unfortunately. I've never wanted to spend the big bucks on an adjustable one so I've done a lot of trial and error lol. I need some details on your engine though. Compression, what is the cam that's in there, what carb. , what can you tell me? Also what is the pcv valve you currently run? Do you know what it's supposed to be for?
Thanks I'll take it to PM as not jump on someone else's thread.
 

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There are pcv valves with fixed orifices also. Nothing inside them, just a hole drilled in them no moving parts. I think they were used in high performance applications. When I first started tuning my engine, when I got to the pcv I tried lots of different off the shelf parts based on the original engines they came on. I eventually gave up and bought the adjustable and it works great. My engine has about 11”Hg of vacuum at idle, this was causing my valve to flutter.

Question: Does your idle fluctuate at all? Mine did, and it was because of the improper pcv valve.
 

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There are pcv valves with fixed orifices also. Nothing inside them, just a hole drilled in them no moving parts. I think they were used in high performance applications. When I first started tuning my engine, when I got to the pcv I tried lots of different off the shelf parts based on the original engines they came on. I eventually gave up and bought the adjustable and it works great. My engine has about 11”Hg of vacuum at idle, this was causing my valve to flutter.

Question: Does your idle fluctuate at all? Mine did, and it was because of the improper pcv valve.

Yes to all of this. I have even less vacuum than you. I cured my issue by using a pcv from a 1967 Corvette with the 427. Had solid lifters and low vacuum. Fixed my problem and works great. Another one for those with slightly more vacuum that sometimes works if from the old solid lifter 302 engines. My vacuum is around 7-9 so I use the one from the Vette
 

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I looked it up on Rock Auto and a 67 Corvette with 427 uses a PCV Fram FV181. I will give that try.
 

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Ticking noise

Don't use a cheap pcv valve---just get an A/C Delco--CV774C---part #6487779. I ran into this before using Napa valves,even though their listing is correct for a 70s v-8 Chevy.
 

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I looked it up on Rock Auto and a 67 Corvette with 427 uses a PCV Fram FV181. I will give that try.
I look mine up for that application also or something like the 1st gen Camaro with the DZ302 when running a nice cam.
 

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I have a hand vacuum pump with a gauge on it...I used it to test off the shelf PCV valves. Never found one that met the specifications that it was supposed to meet.
 

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Just thinking here....You just rebuilt the motor so she's tight... Did you adjust the idle mixture screw(s) to get the proper vacuum, then see if the noise goes away?

You may simply have to much vacuum.

Then if its still present:

Use mechanics stethoscope to listen directly on the PVC to see if it the PVC...you may have to add an extension of sorts to the bottom of the PCV to place the valve outside of the Valve cover too se if its the PVC or not.
 
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