Cams clicking--need a new camshaft?

[Guest Jon8RFC]

I'm not positive, but here's what I wrote to my brother-in-law about his 1977 280Z...it smells of gasoline when the car is running

So I started doing some research in the hopes of fixing the valve problem, but I've found a worse problem--gasoline. The ambient smell is a tiny part of the big problem of having gasoline mixing into the oil!!! I looked in the vavle cover through the oil cap and it was smoking after running not even 5 minutes! I pulled the dipstick out and took a smell...gas. I took a smell from the valve cover and smelled it there too. I don't think we should start it up again until we change/add oil and have some additional on-hand. After reading, one person said that with their pushrods it would quiet down after 10 minutes or so...well, we have cams instead of pushrods. I'm starting to think that nothing is seized and gunked up. I'm wondering if one of the lobes on the camshaft is rubbed off to the point that when it's supposed to be smoothly opening/closing the valve, it opens a little, then there isn't enough lobe left to close it with recriprocated pressure, and it just snaps shut (the clicking sound) under the closing-pressure of the spring holding the valve in place. This is my speculation after thinking about how camshafts work and the loud clicking sound. I could be way wrong, and I can only see the top portion of one lobe when looking down into the cover, so I don't have other lobes to compare it to. Since it needs a serious oil change/replenishment, I say have a machanic take off the valve cover while he's draining the oil and give the camshaft a look-over.

So, my original thought was that since it sat idle for a few years, oil gunked up and seized a valve, but I'm not thinking that anymore. Can anybody confirm or disprove my lobe-hypothesis? At ~800rpm idle, it clicks in the first video; in the second video, the clicking is proportionate to the revving I do. This makes me think that it's not the intake manifold or the other possibly loose something, since it's in sync with the rest. Also, the other day, I tested to find which cylinder was having the problem by disconnecting spark plugs and the engine didn't really react differently when I disconnected the spark plug of the very front cylinder, but did when I disconnected the 2nd or 3rd...so that's another reason that I suspect it is a valve issue rather than a loose manifold...right?

 

Here are a couple videos, with sound, taken with my cell phone. I had to convert them to a more common format (originally *.3g2), and the shareware software I used put an ugly watermark on the videos :/ They're encoded using divx.

jon8rfc_280z_clicking.zip

[veritech-z]

If it sat for any significant length of time, you ought to do a general tune up on it anyway probably. You might try checking the valve adjustment, valve cover gaskets are cheap. Also, did you check for broken/loose/missing exhaust manifold studs? Sometimes exhaust leaks can sound pretty dramatic. Listening to your sound clips it did sound more like a valve to me, but it's hard to tell.

[Zmanco]

It does sound more like a valve being way out of adjustment, but that alone would not explain gas in the oil. I suppose a failed injector that was dumping too much fuel might result in gas running by the rings into the crank case, but the ticking sound is much louder than an injector I think.

 

I agree with veritech-z that you should take the valve cover off. Also, I would not run the engine until I had this figured out. Not only is gas in the oil bad for its lubricating properties, if it's washing down the cylinder walls you can land up "un seating" the rings on that cylinder. (There's probably a better term for this, but it escapes right now.) Not sure if there would be any fix for that except a rebuild.