I think I found the cylinder that is not running optimally

[tokuzumi]

No SES light, but the car definitely wasn't running optimally in the low RPM range. Pulled the plugs on the driver's side. Cylinder 5 (assuming driver's side front to rear is 1/3/5/7) was coated in oil on the threads...no oil pooled in the socket.

Most of you probably know already, but the LS based engines use the same size plug as the LT5, so I swapped out that plug. Gap was significantly smaller than the others. Didn't appear to be mechanically gapped, so I don't think there was any piston contact.

Need to check the passenger plugs, and will use the rest of my NGKs to do a halfway tune up. I won't replace wires or coils for now.PXL_20220705_235729766.jpgIPC_2022-07-05.20.02.42.2530.jpg

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[Hib Halverson]

That plug is badly oil fouled. I'm not sure about what I saw in the second image. By chance is that the piston top shot through a bore scope?

In any event, you may have a problem with a valve seal or a broken ring.

[tokuzumi]

Second picture is from an endoscope.

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[tokuzumi]

Originally Posted by Hib Halverson

In any event, you may have a problem with a valve seal or a broken ring.

I'm hoping my issue is the former. But after Googling what causes the oil smoke (under hard acceleration), it is looking like the latter

[tokuzumi]

Car runs smooth as glass now. Interesting how things run when all cylinders are firing.

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[WARP TEN]

Wouldn't a compression test reveal if there is a broken ring? Why not try that. --Bob

[XfireZ51]

Originally Posted by WARP TEN

Wouldn't a compression test reveal if there is a broken ring? Why not try that. --Bob

Bob,

Had a similar situation with my old block. Compression tested fine even though compression ring was cracked in 4 places from detonation due to a bad injector. However, I was getting oil smoke under acceleration.
Depending on which cylinder, ie 1/3 or 2/4, could be injector housing gasket allowing oil seepage from one of the oil windage ports.

[tokuzumi]

Originally Posted by XfireZ51

Bob,

Had a similar situation with my old block. Compression tested fine even though compression ring was cracked in 4 places from detonation due to a bad injector. However, I was getting oil smoke under acceleration.
Depending on which cylinder, ie 1/3 or 2/4, could be injector housing gasket allowing oil seepage from one of the oil windage ports.

I'm assuming the cylinder numbers are like the small block Chevy so it was piston 5 (3rd from front driver side).

I can pull the plenum at a later time and get the injectors cleaned and flow tested to ensure proper operation. Slap some new o rings and see what happens.

But if I had to do some engine upgrades....

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[XfireZ51]

Originally Posted by tokuzumi

I'm assuming the cylinder numbers are like the small block Chevy so it was piston 5 (3rd from front driver side).

I can pull the plenum at a later time and get the injectors cleaned and flow tested to ensure proper operation. Slap some new o rings and see what happens.

But if I had to do some engine upgrades....

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If you are going to have injectors flow tested, then go thru the process of flow matching the injector pairs if needed. Some injectors may need to have harness locking tab removed to do this.

[tokuzumi]

Originally Posted by XfireZ51

If you are going to have injectors flow tested, then go thru the process of flow matching the injector pairs if needed. Some injectors may need to have harness locking tab removed to do this.

I'm in the Atlanta Georgia area, but could ship them somewhere.

Would it be best to ship to a company that knows the LT5, or would any reputable injector refurb place be up to the task?