Hello everyone... lately I've been having some problems with my 350 small block. The motor has 5000-8000KM's. Im not 100% sure but I believe its a hydraulic tappet cam. The heads are GM fastburn vortec (12464298). It started 3 weeks ago when we were having colder weather... I usually let the car idle for 5 minutes to warm things up ( If I do not do this on cold days the oil pressure will rise past 60PSI, I like to keep it under that all times). The noise started out as a very small ticking during idle. Just last week it escalated into more of a rattling noise, almost like a small ball bearing on top of a vibrating surface. I think I can hear it while cruising down the road but I can never really tell. The first second when it fired today and before oil got pumped throughout, it was a really sharp noise, then it faded into the tapping/vibrating.

The valve cover was pulled and the springs/rockers were all checked. Nothing was loose... great oil flow through the heads. After assembling everything back together the same noise is there still. I mentioned above that I think its a hydraulic cam... does this sound like a lifter problem? During the first 5 minutes of my cruise today the car shut off and would not fire back up... fearing the worst I got a friend to tow me the few minutes home and long behold she fired right up for us with the same small rattling noise. I probably had it flooded before the tow but I didn't want to take a chance and keep cranking her.

Here's what I think... the oil pressure might having reached 70-80 PSI at some point during a cold start. What could high oil pressure damage when it comes to the internals of the camshaft/head? I hope I did not damage a bearing.

Forgot to mention, there is no real loss of power. However in the past 3 weeks there have been 2 separate occasions where I have went to give it some power, and there was a small hesitation. Nothing serious maybe .5 of a second.

Here is a video, skip to about 45 seconds to start hearing the noise

http://www.youtube.com/watch?v=Dc1rb...ature=youtu.be

 

Tappet = lifter

I'm guessing you mean, "hydraulic FLAT tappet", as opposed to "hydraulic ROLLER tappet"?

No, high oil pressure won't damage anything. Whatever the problem is, if anything, it's not that.

When you had the valve cover off, were all the valves moving about the same amount? Any of them need adjustment more than others? Any broken springs, bent push rods, galled rocker *****? In short, what did you SEE?

Is the "rattling noise" at crank speed, or valve train speed? Is it coming from the front? rear? left? right? top? bottom? of the motor?

 

Sorry, yes I mean't flat tappet. When the valve cover was off everything looking very good. I had originally thought it was a valve spring or rocker but they were all in great working order, I did not adjust anything but I did I thread count and everything lined up with each other. Nothing was actually loose or visually damaged.

The rattling/vibrating sound happens at 700-1000 RPM and is louder when the engine is cold. When you bring the motor past 1000, the sound seems to smooth out, but sometimes I think I can hear it when Im cruising on the highway. When the motor is hot you can still hear the noise but its not as loud.

The only indication I have of where its coming from is the sound (the right side head area) and the vibrations when the car is idling. I can put my hand on the valve cover over cylinder #1 / #3 and I can feel a small vibration of the noise. It doesn't seem to be anything hitting the top of the cover. With my hand on the passenger side valve cover, it feels 'smoother' without the small rattling feeling.

 

this description leads me to believe you have the beginnings of rod knock happening. Sometimes its difficult to distinguish between upper end noise (bent valve, flat cam lobe, sunk lifter) and bottom end noise (bad main or rod bearing) without some prior experience with the sounds.

In either case I would start doing some additional investigating and stop driving the car until its sorted out. You could end up completely destroying the engine, but if you fix it soon may save the motor entirely.

 

A long screwdriver or even a piece of a small broom handle makes a good listening device. Just put your ear right over the end of it and touch it to parts of the head and block and try to locate the noise a little better. You can also get a mechanics stethescope from harbor freight for real cheap.

 

one thing you might try is while the car is off, hook onto the front pulley and with a ratchet slowly rotate your engine. after each 1/4 turn recheck your rocker arms.. seems to me that one of your push rods may have bent and its possible that when your cam rolls to the down position on that rod it may be separating from your lifter. Might seem alright right now with how your cam might be pushing your rocker arm in the up position causing for there to be no gap. when I first fired up my last engine this happened and I couldnt figure out where the noise was coming from. after doing what I just mentioned I found there was 1 push rod that was slightly bent and was causing a ticking noise when it was dropping lose from the rocker arm and then getting pushed back into it.

 

Thanks for the input everyone... the sound I hear doesn't sound like a rod issue but I could be wrong. I have taken a video with a good sound clip showing the noise and general area. I have watched other videos on youtube of people with broken lifters and it seems like a slower louder click. My car idles around 700-800 RPM and the ticking seems to be almost at least twice as fast which could back up what your saying Ronnie. Thats a good point, if the pushrod is bent it could be 'bouncing' up and down when theres no real load during idle. The video is uploading but it seems to be taking a while so I will post it when its finished.

Snapped this picture however, and if I put my finger on top of the fitting circled, you can feel the ticking fairly strong. Even if I hold the rubber tubing down the line towards the other head I can feel it slightly.

 

hmmm... you dont see your pcv valve moving when your engine is running?? another thought since you could feel it when holding down on your pcv valve, your rocker arms (possibly 2) are coming up and hitting the bottom of your pcv valve?? try pulling your valve up a bit for clearance....

 

those look like 4" valve covers or are they 3" if 3" and you have the wrong length push rods or 1.6 lift instead of 1.5 lift rockers they could be tapping on your valve or even on your covers period..... just another though that you could look into.

 

I'll try to pull on the valve, maybe the rubber grommit got pushed in a little farther then it should have? That would be an easy fix. Although I had the vehicle last year with no problems, only this year a week or two after coming out of storage.

Here is the video I took. You can hear it well after I give the motor some throttle and then it revs down. Skip to about 45 seconds and thats when the sound started louder. Like I mentioned before, its not a slow tick that most people report with a broken lifter... its about twice as fast and more of a ticking that comes on periodically when the motor is idling. Ronnie, maybe this sounds similar to the slightly bent pushrod you experienced? That seems like something that is very possible.

http://www.youtube.com/watch?v=Dc1rb...ature=youtu.be

 

From your various descriptions, it just sounds like the pcv valve operating normally.

Disconnect the hose temporarily, see if the ticking stops.

 

yeah sounds like the PCV valve is chattering to me. Might want to double check the vacuum source to it and also check around for any other possible vacuum leaks.

 

I'll check the valve first thing tomorrow morning. The car is in for the night and there would be alot of unhappy people if I had to fire it up right now... I do hope its the valve. I sure would feel like I wasted time pulling the valve cover for nothing! Thanks alot everyone, I'll post my results before I leave for work tomorrow.

 

Yup, the PCV valve itself often makes a kind of rattling noise, as part of its normal operation... but sometimes when they get partly blocked the little valve thing in there has to move alot farther and makes a funky noise.

Pull it out of the grommet and listen to it.

 

Some other things to check, cracked flex plate, exhaust gasket leak..
Also move your plug wire away from the 2nd tube back on the dr side, it looks a bit close.

 

Well folks, it was indeed the PCV valve. Alot better then a lifter or pushrod! a little over reacting on my part but since the motor is so new I didn't want to rule anything out. That would also explain why I stalled yesterday. Thanks alot everyone... saved me a big headache. Funny thing is that I had a Friend/ GM mechanic come over and listen. He told me lifter... good thing I didn't drop it off at a shop! Thank you so much everyone.

 

good to see your problem is fixed and was a small one was it the actual pcv valve? or was it seated too low?? Curious...