Cam opinions needed - appears to be severely worn (1978 280z)

[johnny haywire]

Oil/filters are cheap. I did a buddies that was sludged and rusty. I adjusted the valves, swapped the oil three times (500 miles per), readjusted the valves. Ran great and was all cleaned out. Yours has no sludge at all...

Good point. I'm thinking the rust came from condensation and time, sitting for 14 years. Oil pressure is very good, according to the gauge on the car. I'd be much happier not dealing with a cam swap right now...

[GreenZZZ]

Have any of you ran the engine with the valve cover off? I'd like to do that to make sure none of the oil ports in the cam lobes are clogged, but I'm curious as to whether there will be oil spraying everywhere if I do that.

Take the oil filler off and you'll get an idea of the splatter you get from one lobe with a Z at idle.

[johnny haywire]

Ha-ha! Got it, thanks!

[olzed]

I would run it with the cam cover off for a minute to check oil flow to the cams. You will get a bit of splash but it's not a big deal.

Helps to preserve the bodywork.

[grannyknot]

One point my father brought it up is the fact that since the rust hasn't been polished off after 3,000 miles, there is no metal-on-metal contact, a good thing.

Johnny, what I don't understand is how after 3000 miles that the rust HASN"T been polished off. Think of the resisting pressure from the valve springs and cam lobes that at high rpms are slamming the rocker down, rust is not very strong.

A butter knife scraped sideways over the cam lobes would remove most of that rust.

Perhaps there is rust on the valve seats as well, just thinking out loud as I type, I'm probably way off base.

[Walter Moore]

Johnny, what I don't understand is how after 3000 miles that the rust HASN"T been polished off. Think of the resisting pressure from the valve springs and cam lobes that at high rpms are slamming the rocker down, rust is not very strong.

A butter knife scraped sideways over the cam lobes would remove most of that rust.

Perhaps there is rust on the valve seats as well, just thinking out loud as I type, I'm probably way off base.

Where the rust is on the cam, there is supposed to be clearance between the lobe and the rocker arm anyway. That is why it is still there after 3000 miles.

[240260280z]

They clean up real good:

[Captain Obvious]

Couple of problems running with the cam cover off...

First... Yes, if your oil pressure is healthy, you'll have oil flying everywhere. It won't shoot twenty feet out of the holes in the lobes, but it will definately leave the engine.

Second, since you've got EFI, it will confuse the ECU because of the way the PCV system works. You'll have to plug the tube that normally connects to the cam cover, and you'll have to pull the tube off the PCV valve and cap off the PCV valve as well.

If I were you, I'd pull the cam cover off, pull the plugs out (so the engine spins faster) and pull the coil wire off and then crank the engine to see what happens. With the plugs out, it should spin fast enough to get a good idea of how far stuff shoots. In fact, even at that speed, it may shoot far enough to leave the engine. :laugh:

[Zed Head]

You've already driven 3,000 miles with the rusty cam, plus whatever mileage the PO put on it after starting it after 14 years. The main problem here just seems to be the clicking noise after the valve adjustment. When rust forms, it actually causes an increase in dimensions overall (Rust grows - I have actually done a little bit of work involving spalling of metal re-inforced concrete due to rusting rebar in bridges), even though after cleaning it off there are pits. So it may be that the feeler gauges are riding on the rust of the base circle (one reason the rust hasn't worn off of the base circle of the cam lobe is that there is/was clearance there - no rubbing) leading to an increase in actual rubbing parts clearance.

Just a thought, and maybe a simpler path to getting rid of the clicking. If it hasn't fallen apart in 3,000 miles, it will probably survive a Scotchbrite buffing. Then you can set proper lash and live fairly quietly ever after.

[olzed]

Thats impressive BLUE. Obviously the hardened cam doesn't pit too much. JOHNNY HAYWIRE might be lucky, and save the cam.

[johnny haywire]

Once again, thanks for all the excellent insight. I'd like to buy you all a beer! I'm not nearly as disappointed as I was a few days ago (Blue - that cam cleaned up beautifully!!). I'll probably crack the cover open again this weekend and see what I can clean up with out pulling the cam. Sadly, that pretty much means no abrasives, but I should be able to pull the rockers one by one without screwing up anything, right?

[olzed]

but I should be able to pull the rockers one by one without screwing up anything, right?

Pull the rockers one at a time. Yes.

Keep us posted.