'78 280Z making ticking noise when engine warms up

[dankfrye@charter.net]

I've been working on a problem for several of months that I can't figure out. When my engine warms up all the way, it starts making a ticking noise. It is worse under load. I first thought of an exhaust leak but they usually happen cold and go away when things warm up. By pulling off one plug wire at a time and one injector plug at a time, I have narrowed it to #6 cylinder. I swapped #5 and #6 plugs, then #5 and #6 plug wires and the noise was still in #6 cylinder. I took #6 injector out and tested the spray. It looked good, but I cleaned it several times any way. I then switched #5 and #6 fuel injectors but the ticking still came from #6 position. I have replaced all my hoses, have a new distributer (my vac advance wasn't working. I have removed all of my EGR stuff and have a non EGR manifold. I have also disconnected my BCDD valve. I have all new fluids. I noticed the ticking right after adjusting the timing and the valves. After buying my new distributer, I reset my timing to 10deg TDC with the vacuum advance capped off. I thought that I might have got the valves a little tight so I re-adjusted them again. The problem has not changed. I'm running 93 Octane, non ethanol gas. The car runs good and idles steady but the noise gets really annoying when the engine warms up. Sorry this is so long but I didn't want to leave anything out. I would really appreciate any input that anyone has on this problem.

Thanks,

Dan Frye

[cozye]

It doesn't tick when the plug wire is off number 6?

[dankfrye@charter.net]

No! When I take either the plug wire or the FI connector off the ticking goes away. Some how it's related to #6 cylinder.

[CW240Z]

Could be a sticky rocker arm. Mine on cylinder 5 ticks when the car starts up, but quiets down a bit after it has warmed up and oil has been pumped through the system.

[cozye]

Definite exhaust manifold leak. It's common. If it where a valve train related tick it would do it whether you had combustion or not since the cam is still spinning and opening th valves

[dankfrye@charter.net]

Thanks! I suspected that but I thought that most exhaust manifolds mostly leaked when everything was cold then went away when things warmed up Gaskets expanding and such). I'm still kinda of new to this.

[cozye]

Thanks! I suspected that but I thought that most exhaust manifolds mostly leaked when everything was cold then went away when things warmed up Gaskets expanding and such). I'm still kinda of new to this.

I suppose the going away when hot thing is possible, but that's not the norm. On these cars the end bolts like to snap off due to rust, heat, and warpage. Especially on 1 or 6 at the end. It's not too bad a job if you take your time, use lots of heat and pb blaster. Don't get impatient and work the bolts slowly back and forth very gently. Nissan still makes the gasket, which is higher quality than the replacements

[dankfrye@charter.net]

I have already replaced the gasket. It don't go away when it's hot though. It starts ticking when it gets hot; just the opposite.

Thanks

[FastWoman]

I would normally agree with Cozye -- probably an exhaust leak at the manifold/head junction. However, if you're SURE you don't have a leak there, it might be a sticking valve or rocker that gets popped shut when there's detonation in the cylinder. You can try using a motor flush like Gunk. Only do this if there aren't heavy crusty deposits in your engine. Gunk is a great way to flush away the varnish and get your valves moving freely. You might also need to SeaFoam your intake.

[cozye]

Didn't you check the manifold for warpage or cracks? Some owners have to get the manifold milled down to straighten the maiting surface.

[cozye]

Poor some seafoam in while running and see if it blows smoke out the suspect area

[dankfrye@charter.net]

Thanks for your suggestions. I was contiplating using Gunk valve medic or something similar but I was afraid that I might break some deposts loose and clog up my oil pump. My valve train does look prettty clean though so I might try it. I have cleaned my intake and throttle body both off and on the car so I think it's pretty clean. I have also taken my injectors out, cleaned them and tested the spray pattern. I guess the exhaust manifold could possibly have a leak. I have some sea foam and might give that a try.