2001 Z06. 71.5k miles. I've had it since 28k and though I've raced it some, have taken care of it. It has always smoked some at high rpms which I talked up to "loose piston rings from the factory" and "piston ring flutter."

For the past few months I started getting into motorcycles and drove the vette less and less. Well yesterday I drove it some and while driving noticed the CEL flash some and then stay on. I pulled the codes and the only one was P0700 "multiple misfire." That's the only one. I felt like there was some lack of power but I thought maybe it was due to me having gotten used to the motorcycles.. It seemed to idle fine, didn't hear any unusual backfires, or any unusual ticking (it's always made valvetrain sewing machine noises.)

Pulled the plugs and number 7 is caked in oil.



So did a compression test on it and it won't read anything really. The number 5 read around 135 though the plug adapter might have been slightly loose for it. I got number 7 as tight as I could with no wiggle and still no reading.

Pulled the covers off just to see if it were something "easy"..but looks like the springs and rods and rockers are fine over there.



I will try pouring a little oil in the plug hole to see if it gets any reading (to know if rings or not). My guess at this point is stuck or broken valve? I'm really hoping it's not rings or piston..



The real kicker? I've got a guy flying in next weekend to buy it. FML

 

Leak down test and listen to where the air is going?

Borescope?

 

A good friend of mine has an 01 z06 and his did the exact same thing, except it blew his motor. From what I've read a lot of 2001 z06's do this with the piston rings.

 

I'm holding out a tiny bit of hope that it's something in the heads and not piston/rings related...if I have to rebuild this engine at this point in time then FML.

 

either a cracked ringland or a fragged exhaust valve. oil burners almost always blow up in one of these two ways. the exhaust valves lose their ability to transfer heat when you cake them in oil. remember the exhaust valve only cools itself on the seat and on the guide. oil coating it is like wrapping it in a blanket. eventually they get brittle and one batch of detonation is enough to crack the valve. ringlands work similar only the oil caking can sometimes light up the whole piston.

i've blown up engines both ways and really, it doesn't matter which one it is. if it's a valve you would be nuts not to do a rehone and new rings. if your bearings are in good shape and there's no cylinder wall damage you may be able to get by with a ball hone and new ringset

heads will need all new exhaust valves, you can reuse your intakes though, valve job, new seals and you should be up and running

worst part is how labor intensive it is

 

Why in the world is there a "Family Dollar" sticker under my manifold?? And why is it SO DIRTY under there?? I'm starting to wonder if this is really a 70k mile engine....

 

Haven't driven it in a while and all that crap to me spells mice. I suspect the ring land on the piston. Anyone you know have a borescope?

 

common in rural areas, more dirt on the roads. in the air. mice running in the fields setting up shop under the hood in the winter

 

Update:

Valvetrain looked good. Seals looked good. I'll be taking the assembled head over to NAPA to have them pressure test it Monday.

Now I'm going to drain the oil and pull out the one piston to see if it has seized rings or ring parts in the pan.

Pics:

#7 is far left

 

If I want to remove JUST the number 7 piston, should I have it all the way up or down?

 

So far that seems really weird - since you are seeing NO visible problems or damage!

(1) What did the oil look like?
(2) What does the oil smell like?

Thanks,Matt

 

Put it in the easiest position so you can pull the rod cap off and re-torque it later, which is at the bottom

Make sure you put some vacuum hose or a rubber cap over the ROD STUDS - so on removal and re-install you do not scuff the crank -

Yes! this will happen if you do not take precautions

Thanks,Matt

 

I know man, I'm tearing my hair out with second-guessings and stuff. It's too late to wonder if I got an accurate reading from that compression gauge..

I'm dropping the oil pan now and will let you know what the oil looks like. Smells like oil I guess.. Possible that gas could have gotten in it (plug not firing so dumping gas in there?) but I don't remember.

It's just really weird that I have NO signs of any damage.

Could you elaborate (or with pics) the vacuum hose/rubber cap thing? I'm not able to visualize it.

 

At this point....being that the heads are off already. Which option should I take, given that I haven't found anything wrong yet?

1) Get all the new gaskets and stuff and put it back together and re-compression check it, since I'm not 100% sure I got an accurate reading (might not have been screwed in tight enough. Didn't try the teaspoon of oil in the spark plug hole check. Didn't do a leakdown test.

2) Pull the number 7 piston and check the rings. Have a shop do a pressure test of the heads.

 

If you didn't get any reading on compression test that's a big leak. Squirt some WD_40 down in the valve seats off the bad cylinder head and see if valve leaks. Try to pressurizer that cylinder with a piece off wood with a rubber gasket to cover and make a hole in the wood and get a air hose. With that bad off a leak trying to pressurize that cylinder. Just a generic check maybe something will show it's face .

 

curious to see the piston. you can kill ringlands and from the top the piston will look fine

there's a pic of just such a thing in this thread

http://honda-tech.com/showthread.php?t=3127913

the caps on the rod comment could be done with a section of fuel injection hose or vacuum caps. slip it over the threads so you don't scratch the crank pulling out

that engine of yours was using a lot of oil. since you have it apart i would honestly replace all 8 exhaust valves, do a valve job on both heads and buy a new set of the improved GM rings with the higher tension oil rings. the only question is what to do about the #7 hole. the GM service sheet says to replace the oil and second ring in oil burners but not the top unless you rehone. honing with an engine in the car is.....well i've never even tried it. have seen guys do it with an 800rpm milwaukee drill and ball hone but all those little bits of grit will wind up going somewhere. if you do it try and be as clean as possible so grit doesn't get in the crank and oil system

 

Thanks guys.

Does anyone know how I pull off this oil pan to get to the bottom of the rods? I pulled off the lower section but there's that upper section of the pan..

 

Caps on the ROD Studs in #44 - quickest one I could find

http://www.yotatech.com/f116/22r-reb...84/index3.html

Thanks,Matt

 

Upper section must come off in order to access the rod studs -

Cradle must be dropped enough and motor supported to get pan out of the way -

At this point I would:

(1) Continue to pull it apart and do a thorough inspection

(2) Order all gaskets needed in order to re-assemble "AFTER" you know exactly what you are going to need

(3) At this point I would pull the block out from the top!

Here is a write-up I did on how to do this:

http://forums.corvetteforum.com/c5-g...ring-jack.html

And my work I had to do:

http://forums.corvetteforum.com/c5-f...rk-myself.html

Thanks,Matt

 

http://forums.corvetteforum.com/c5-t...n-removal.html

http://forums.corvetteforum.com/c5-t...ng-torque.html

Thanks,Matt