1977 280z Odd Tapping Noise

[ckurtz2]

Hey Guys,

I have been trying to tackle an elusive problem on my Z that has been happening since late last Spring. The issue is that During a cold start, the engine taps extremely loudly for the first few seconds, then goes away and it sounds normal. Then once it is warm it seems to just slightly tap, but not nearly as loud. 

If I let it sit for a little and then start it hot it will tap loud again during startup. However, sometimes about every 10 starts (different days) during hot or cold start I won't hear any noise.

I tracked the tapping sound to the head toward the front of the valve cover. I am thinking 2 or 3 valves back from the front. However, I have set valve lash multiple times (confirmed good by other peers) and it still taps. I even tightened much tighter than spec (temporarily) and the tap is still there. Rocker pad, lash pad, cam are smooth and not damaged. Rocker arm was replaced, and no difference.

My thought is whatever the problem is, it is oil-related, because it happens during a cold start and oil isn't in the head yet, or when the oil film is thinner when hot (just my guess). 

Keep in mind this head was rebuilt not too long before the noise appeared and was good for several hundred miles until this started happening. 

Can someone share insight on what else it could be and how to test it?

maybe exhaust leak? (I don't think it is, you can be the judge from the video/ audo recording).

Could a valve spring or guide do this? Maybe the rocker pivot (do these even go bad). I am kind of stumped. I did have a valve rocker pop off the lash pad around the area where I heard the noise. But the noise started long before that happened, and the rocker hasn't popped off since, so I would not think they are correlated, but not sure. Here is link to that thread.

 

Thank you in advance.

[dutchzcarguy]

Hi, I'm not hearing a lot.. (I got near perfect hearing)  Maybe you could put the microphone on different spots in the engineroom and take a bit longer video.

Have you used the "screwdriver against your ear" method?  You take a long screwdriver, put it somewhere on the engine and hold your ear against the handle top..  The things you can hear!  It's amazing..

It's oilpressure related.. i agree, maybe test a 20w40 oil is your using 10w40? 

I looked up tempe and your living in a hot state.. I would use 15 or 20w40 or 20w50 oil.

[Patcon]

I would take off the valve cover and pour some oil or put some prelube on the second cylinder valves. Set the valve cover on and start it up. If it taps, repeat on cylinder 3. If i make it go away, I would look at oil delivery. External spray bar or through cam?

Possibly replace the oil pump or go to the turbo pump. Heavier oil might help overall but will delay oil delivery when cold.

[ckurtz2]

I would agree it is oil-related. I did switch to the 280zx Turbo Oil Pump, but that did not help. I have also changed the oil and that helped, but noise was back within a few starts. It is internally oiled with external oil bar blocked off.

I am running Valvoline VR1 Racing Oil that is 20w50. 

Yes, for now just try and focus on the noise at startup. Sounds kind of like a clack clack clack before going away. in the MP3 it is from 019-022. I wish I had a better microphone, but the fan drowns out the noise. It is concerningly loud if I could find a device to pick up the noise properly. When the noise comes back when the motor is hot (not in any of the videos I provided) like I have done the screwdriver test many times and it definetly comes back to the head where the cylinder 1 intake valve is, or maybe one valve further back. Could also be in Cam bearing area around there. However, the rest of the valve cover is quiet.

 

[Patcon]

You could take the fan belt off. It can run for a minute or so without any damage. That will make it easier to hear

[Yarb]

How long since the engine had a refresh

[dutchzcarguy]

12 hours ago, ckurtz2 said:

Sounds kind of like a clack clack clack before going away.

Any engine that's started cold makes these noises, that's normal as there is in the first 3-5 seconds no oil between the moving parts in the head.

But i guess you know this..  Why are you using racing oil? Get a good 15 or 20W40 or 50 and test. Maybe a enginecleaner to the old oil, let it run warm and put some new oil in. Take a good look at the old oil.. no metal flakes or so? And open up the oilfilter and look for metal parts..  Maybe this engine wasn't very well put together when it had a rebuild i don't know..

Guess you now can find out what i always wanted to know.. does the oil flow from the inside to the outside in the oilfilter or visaversa? 🙂

[dutchzcarguy]

btw.. use a sharp chisel (woodchisel) to open up the oilfilter (Near the connecting end) do not use a hacksaw, Hihi..  as they make lots of metalflakes..  first woodchisel, then scissors can be used.

Edited January 1 by dutchzcarguy

[Zed Head]

Maybe the chain tensioner is loose and it takes a few revolutions to pump up.

[siteunseen]

8 hours ago, dutchzcarguy said:

i always wanted to know.. does the oil flow from the inside to the outside in the oilfilter or visaversa? 🙂

In the small holes, out the big one.

Edited January 1 by siteunseen

[Yarb]

History on the engine would give us a lot more possibilities for what you’re experiencing.

[siteunseen]

Hows the pressure gauge reading when it does this?

They cylinder head shop may have put weak springs back on your head. Just guessing from far away.