I just rebuilt my C5 Z06 (6.0 Iron Block bored .30 over 4 inch crank) 408 stoker. It went under the knife the first time because the oil rings went bad. So I broke it in for about 450 miles or so with many heat cycles never over 3k rpms and I was hitting on it (no detonation or spark rattle engine sounded great) when I missed 4th because my shifter is too far back and it doesn't fully engage 2nd 4th and 6th some time apparently I hit the rev limiter at 6800 or 7k like 3 times. Oil blew out of the exhaust yet the car continued to run fine, good oil pressure, good temp, etc... I had hit on the car probably 20 times before this happened with no problem at all. I am not sure exactly what it could be I pulled the passanger side plugs out and 3 of them had oil on the thread, 2, 6, 8

I am thinking either a Headgasket (LS9's with ARP Studs) or Rings (Chromoly).
I did not check the coolant or the plugs on the drivers side as I hate my car right now and am tired I will check them tomorrow and do a leakdown test on the car but until then any experience?

 

Rings not seated to cylinder yet. Engine runs fine other wise I'd give it a little longer pull your plugs and check again. Was there any oil on the head near the plug wells? Possibility that the oil ended up on the threads when the plugs were pulled out?

 

.....for anyone that does not already know, the above diagram is not for an LS motor........

 

I mean, it is the same firing sequence correct?

 

I am not sure, wouldn't the car had been smoking from hit number 1 if the rings weren't seated or could it all of a sudden have done that?

 

No......not since model year 97.....

 

Besides the fact that this helps me not, they renumbered the pistons how they are in the block? I understand the sequence is different. Pretty obvious with the picture having a distributor cap and all but I was almost positive the numbers were the same.

 

Other members use these threads for reference, so I'm just clarifying that the diagram is not for an LS engine. The LS firing order is 1-8-7-2-6-5-4-3, and yes...the cylinders are in the same locations by number.

As far as your issue, I'm not sure what info you are looking for. Obviously, continuing to bounce off the rev limiter is not good practice. You have provided no DTC codes, and say the engine runs fine....and oil pressure, coolant temp, etc....are normal. So if you do not hear any knocking/ticking, and the engine is not smoking....do a leak down test....and feel better.

 

I have no dtc codes and is still puffing smoke at idle.

 

Time for a leak down then. You can start with the cylinders whose plugs look oil fouled/questionable. Also do a compression test for comparison.

 

1. What head work was done?

2. Were valve seals replaced?

3. If head work was accomplished, did you apply sealant to the rocker pedestal stud threads?

4. Leak down test will confirm compression ring issues. Not oil ring issues.

5. What ring end gap figures were used?

6. What was the reason contributed to the original oil rings going bad and did it cause any cylinder damage??

7. Who is repairing the engine?

BC

 

1. Yes, they were ported
2. Yes, it had a valve job done 2300 miles ago
3. No, could it be smoking that bad because of the studs?
4. Is there a way to detect oil ring issues?
5. Not sure I will have to check with the shop Monday but it was planned to be gapped for a 250 shot of nitrous.
6. The first time I built the engine and did not know that Diamond Pistons needed 4 oil stabilizer rings instead of two. So I put it together only to have it do the exact same thing as it is doing now 1800 miles later after it was dyno tuned. The block is a new block because the old had scar marks.
7. A local Racing Engine company, they specialize in drag cars and circle track cars, but he has done LSX engines before.

 

Try two procedures:

Remove the oil fill cap from the valve cover when the engine is running. If the engine is running correctly, there should be NO air/gasses emitting from the oil fill pipe. The PCV system is designed to remove a slight amount more crank case volume than escapes from the rings.

NEXT

Temporarily disconnect the PVC vacuum line from the intake manifold and PLUG the vacuum port on the manifold. Allow the PCV hose to vent to atmosphere but point it to an area that if oil emits, it will not cause damage or dump on hot exhaust.

Once the vacuum line is disconnected, monitor the amount of gasses escaping from the PCV hose.

If theres a LOT of gas flowing from the hose, you have excessive blow by from the rings

If you extend the hose into a container and take the car for a spirited ride then examine the container, there shouldn't be excessive oil in the container. If you have excessive oil in the container, thats ONE oil entry point into the intake.

IF you still see excessive smoke from the exhaust either theres LOTS of oil still inside the manifold, OR its coming from other areas:

Rocker stud holes in the intake port. Look in the port on the middle of the right side. You will see where the stud hole enters the port. I reduced the length of the mounting fastener by approx 1/8" so mine does not protrude into the port :



- Rings not seating.

BC

 

The leak down test was letting air out faster than I could put it in, I am pretty sure my rings took a dump on me in 500 miles.

 

WOW! Whats your resolve and plans? Hope you have a GOOD relationship with that engine shop.


Good luck and PLEASE report the outcome.

Bill

 

Just a thought..... Rings could have been inatalled UP-SIDE DOWN. Give that a thought.

Bill

 

I am going to pull the engine this weekend, and going to the machine shop tuesday hopefully with the short block... I just don't want to have to bring my mossberg. I really appreciate all the help Bill, I will keep you posted in this thread.

 

Did the same shop do the build on both engines? Two rounds of bad ring seal in less than 1K miles is a little rough.

 

Nah, I built the engine the first time, minus the hone and bore, I did a good job besides forgetting the extra oil ring stabilizers

 

Is it bleeding air down fast on all the cylinders or just a few? Might want to consider pulling the heads first as its possible the valves may have floated and kissed the pistons.