280z 280z 78 Wont idle, Running Rich, out of ideas.

[Dave WM]

95% loss, yikes!! and I presume it was from the head and not the block (with that kind of loss you pretty much have to have a valve issue I would think, or a hole in a piston).

 

[Zed Head]

31 minutes ago, Cyrillink said:

I agree the 4 and 3 are not dirty at all and Cylinders have the most wear on the cam, barely had any valve lash, it was 0.002in and 0.001in barely fit.

Lash gets tighter when the engine warms up.  Might be that the PO ran it hard because it was running poorly and "burnt" some valves.  That just means warped from uneven heating cause they weren't seating all the way.  Not good!

Looks like lash gets about .002" tighter after warmup.  So, you'd have valves hanging open by your numbers.  Might be too late.

[Dave WM]

Hopefully the cam lobes are ok. Rebuilt head for sure based on how clean it is. Next question besides valve lash and valve damage would be lobe damage. I have heard that using the wrong oils can effect lobe wear. conventional thinking is you want a high zinc content oil. I presume the correct viscosity was well. Lots of discussion on oils so will not re hash it hear, but you may want to do some research on this subject, esp if the lobes are worn.

[Captain Obvious]

Looking at the cleanliness of that valve train, it's clear someone has been in there not many miles ago.

How far are you from Flemington?

[Cyrillink]

14 hours ago, Captain Obvious said:

Looking at the cleanliness of that valve train, it's clear someone has been in there not many miles ago.

How far are you from Flemington?

Flemington NJ, prob 45 min maybe less.

 

[Cyrillink]

19 hours ago, Dave WM said:

Hopefully the cam lobes are ok. Rebuilt head for sure based on how clean it is. Next question besides valve lash and valve damage would be lobe damage. I have heard that using the wrong oils can effect lobe wear. conventional thinking is you want a high zinc content oil. I presume the correct viscosity was well. Lots of discussion on oils so will not re hash it hear, but you may want to do some research on this subject, esp if the lobes are worn.

So, Did the full Valve Lash tune up. Cyl 1,2 Good! holds pressure no issues. compression 150. Cyl 3,4 - On a leakdown test Spits air form the other cyl. 5,6 - GOOD! 

 

So, i am assuming - head-gasket 

[Reptoid Overlords]

I can't see the videos on my phone, but if you want more verification on the head gasket you can remove the radiator cap and observe the coolant when applying air to the suspect cyllinders.

 

Bubbles mean head gasket failure, no bubbles mean there probably isn't a head gasket leak as far as coolant passages go. Head gaskets can fail so that there is no coolant problems as well. Sometimes they fail near an oil passage and cause oil leaks.

 

If it's just a compression leak between the two cyllinders though, it might not show up in the radiator in the form of bubbles now that I think about it. What is the compression of cyllinders 2&3?

[Zed Head]

53 minutes ago, Cyrillink said:

So, Did the full Valve Lash tune up. Cyl 1,2 Good! holds pressure no issues. compression 150. Cyl 3,4 - On a leakdown test Spits air form the other cyl. 5,6 - GOOD! 

You're implying that the head gasket is blown between 3 and 4.  That would explain Dave's observation.  The GOOD! news is that the cylinders, pistons, and rings seem to be in good shape.

Looks like head removal is in order.  FUN!

[Dave WM]

Head gaskets whoo hoo, now we are talking fun!!

[Cyrillink]

3 minutes ago, Dave WM said:

Head gaskets whoo hoo, now we are talking fun!!

You saw the video? Yeah i know.

[Dave WM]

Guess the main question is why did it fail, yes the video seems conclusive. Hopefully its something like an improper torque sequence, else maybe a problem with the head, only way to know for sure is going to be to open it up and do a very close visual inspection.

[Zed Head]

On 12/15/2019 at 6:10 PM, Cyrillink said:

Background story; I'm helping a friend of mine fix his 280z with 30,000 miles on it all original. Car has been garage kept all its life. Really really well taken care of. Apparently some one A-hole mechanic tried before me and failed miserably and i don't know what he/she messed up or touched. After them the car didn't even start. Fixed that issue. (FACE PALM) ?‍♂️  

When you try to start the car it tries to start but never does on its own. If you give it gas than the car starts but it is runs rough(motor shaking). Have to keep the gas paddle pressed in just a little to keep it running. Car smokes white/bluish smoke from the tail pipes. (running rich) ( Gas smell). Changed the oil after the previous Mech worked on it smelled like gas was in it. 

All it takes is one overheating and a head gasket can blow.  Maybe the first guy wasn't such an "A-hole" after all.  

Did the engine ever overheat before the car "broke"?  Never really said what the original problem was.