Loud ticking/knocking noise.

[disepyon]

I adjusted my valves according to this: http://www.picturetrail.com/sfx/album/view/1803105 http://www.atlanticz.ca/zclub/techtips/valveadjust/index.html

After I adjusted it I began to hear a ticking noise, very loud as if something is clinging against something else. Its constant, I hear it on idle and through the rpm range. However everything else seems ok, engine idles super smooth (better than before), revs fine, no hesitation. I did a compression check and I got starting from 1-6(165 165 170 170 165 165). I thought maybe the oil tube next to the rocker arms might be rubbing against, but all is fine and I have clearance. I found out that while the engine is running and I unplug spark plug wire to piston 1, the noise stops and of course the engine starts to idle rough like it should. So I swapped the spark plug wire and same symptom, i changed the spark plug it self and same symptom. I dont get it. Whats wrong? Did i bend a valve for piston 1? bad valve spring? I dont get how that would affect that noise if there is no spark. Shouldnt the noise still persist since the cam shaft is still spinning and the rocker and valve/valve spring would then have to move?

I had a snapped stud on exhaust runner 1 and there was a leak on that runner. I took the manifold to the machine shop to get resurfaced and bought a new gasket and i also got the snapped stud out and now i am able to use a bolt. After all that i still get that sound. I though it was the exhaust leak but it isnt. The sound actually gets louder when the car is warmed up.

This is for a 240z l24, all stock.

Anybody have ideas?

Edited June 2, 2012 by disepyon

[d240zx2]

Recheck your valve clearances.

[bobc]

Some random thoughts:

1. If the valve was bent because you set the clearance in error, it would still make the noise whether the spark plug was connected or not. Just disconnecting the wire would not straighten the valve or stop if from hitting the top of the piston.

2. Based on your pressure readings, this shouldn't be it, but I was thinking that perhaps one of the rocker arms is off or the spring came free/isn't seated well. Suggest starting over with your valve setting and give it another try. Make sure all the rockers are seated properly and the springs are seated properly.

[disepyon]

Thanks for the reply fellows. Ive checked the clearance literally like 6 times and made the adjustments needed. Ill check again to see if everything is seated properly, i didnt see anything out of the ordinary though.

[olzed]

Did you have a spark plug out? Has something been dropped into Number 1 cylinder?

[disepyon]

You know thats not a bad idea. I did have the spark plugs out the first time i did the valve clearance. Cant recall anything dropping into the cylinder chamber though. Ill go check. I really dont feel like taking the valve cover off again today, so ill wait to check the valve area tomorrow.

[olzed]

Have a fish around in No.1 cyl with one of those magnet things on a telescopic stem. You might be lucky.

[disepyon]

I just got done fooling around some more and no luck. Nothing in cylinder 1. Guys have to remember that having ignition to cylinder 1 creates the noise.

I replaced the new distributor cap with my old one and that didnt work. I replaced the coil wire and that didnt work. I havent tried to replace the spark plug again, to test, but i doubt that will do anything, if i had no luck last time then wouldnt help me this time, but you never know.

[Zed Head]

Guys have to remember that having ignition to cylinder 1 creates the noise.

I replaced the new distributor cap with my old one and that didnt work. I replaced the coil wire and that didnt work.

You've shown that you have spark, or ignition, to #1. An ignition problem wouldn't be the source of the noise. It would also be pretty interesting if you could have something bouncing around in the cylinder for as many cycles as you've described without the piece exiting through or destroying a valve. It seems unlikely that something is in there and it only makes noise when combustion occurs.

Copied this from your first post - "The sound actually gets louder when the car is warmed up." Valve lash grows when the engine gets warm. Kind of sounds like you left one of the rockers with a loose adjustment. Not sure why removing spark would remove the noise though.

Edited June 2, 2012 by Zed Head

[olzed]

So all you have done is replace a broken stud, and set the valve lash.

The only thing I can think of is an exhaust manifold leak on No 1. The noise disapears when you disconnect the plug wire,

You havn't cracked the exhaust manifold by some chance. Did you tighten it down evenly?

[Zed Head]

That's a more likely possibility.

Over on hybridz, disepyon posted pictures of the exhaust leak and surprise that the leak was on the side with the intact stud, and the broken stud side was sealed. That would be a pretty good sign of a warped sealing surface. If the manifold sealing surface wasn't ground flat, there might still be an leak despite the new studs and gasket.

Exhaust leaks can be hard to fix.

Edited June 2, 2012 by Zed Head

[Diseazd]

Disconnecting a plug wire to see if a noise quits is the way you check for a rod knock......if the noise gets quiet when you disconnect the plug wire it could indicate a loose connecting rod.