Hey guys, even though this is my first thread, I've been using this forum ever since I got my Z06 a couple of years ago. Just wanna thank everybody for all the great information you post. Hopefully you can point me in the correct direction...

Background:

A couple months ago my engine developed a ticking/knocking sound. After the noise started, I ran the car long enough to park it in the garage (less than 90 sec at idle). The engine hasn't been started since, and I'm in the process of removing the heads.

A guy posted a video on Youtube of his engine making a very similar noise. (if you are curious)


Situation:

All fingers are pointing at either a bad lifter or the notorious exhaust valve issue. Replacing the lifters is no big deal; however, I’m not sure about the exhaust valve issue. So far, replacing the OEM intake and exhaust valve guides with bronze guides is a certainty. As far as the valves themselves, I wasn’t planning on replacing the OEM titanium valves, but I will if necessary (input from you guys is appreciated). Common wisdom does suggest replacing the exhaust valves with newer OEM valves or SS valves (again please provide input or share your experience).

You guys should know that the engine is completely stock, and I’m not looking to increase the horsepower in the near future. That being said, I do run the car and have fun with it, so making it more robust is a goal.

Questions:

Will there be any adverse effects to upgrading to the bronze valve guides and reusing the OEM intake valves?

To you guys who have opted to replace the exhaust valves with SS, have you experienced any effects on the engine performance? (I realize that is a loaded question considering very few enthusiast replace only the valves.)

Engine head question: I would like to avoid using the torque-to-yield heads bolts and use ARP head bolts. But, I read that ARP head bolts have fewer bolt threads. Is this a problem? In addition, I read a few posts where ARP torque specs had changed due to some unknown reason. Has ARP finalized their specs?

Lifter Question: In the even the lifter is causing the knocking, should I be concerned about damage to the camshaft?

Sorry for the lengthiness of the post, but many thanks.

 

Check your rockers, missing needle bearings is not uncommon. If all of your lifter rollers are ok your cam should be fine. If you going with arp, get the studs.

 

Thanks martysauto, I checked the rockers; all seems ok. I was able to pull the lifters yesterday. Unfortunately, a lifter roller has significant scaring. The cam lobe has similar scaring.



Does anybody have any idea what would have caused this?

 

Looks to be bronze in the roller and that would come from one of the main bearings, then pushed to the rest of the engine in the oil.
Did the motor loose oil pressure at some point or over boosted to cause a main bearings to fail?


Time for a complete engine tear down, all the journals checked, and both the block (if rebuildable) and the complete oil system in the car clean and flushed to remove any debris before either the block is rebuilt, or the car gets a motor back in it.
Note, some of the oil lines can not be flushed cleaned correctly, and have to be replaced instead.

 

Oh wow. Yeah that is bad. Just the one lifter? Most likely all that metal has filtered through the engine and bearing.

 

That's going to make some noise. Without looking, the cam needs to be replaced. Cause could be lack of lubrication, possibly improper heat treatment, but not likely. Does the roller on the lifter still spin? freely?

 

You are looking at a new cam and lifters at a minimum. A few more bolts and you can have the heads off. Might as well pull the heads and check the guides with a proper valve guide bore gauge (see Hib Halverson's article on measuring valve guides on the Corvette Action Center site for tool recommendations). Then you can decide what to do about replacing the guides/valves, etc.

Pulling the engine might be the correct thing to do if there is a potential issue with the bottom end.

If parts have been wandering through the oil system you will need to clean the dry sump tank and replace the oil cooler (they can't be cleaned sufficiently).

Bill

 

Don't the heads have to come off to pull the lifters?

 

ttt

 

Sorry guys! I've been away for a while. Two answer your questions:

Dano523: I'm afraid you are correct. I just hope I got the car shutdown before any real damage occurred.

C6z06man: Yes sir, one lifter. Just nominal wear on the other lifters and cam lobes.

1HotRodz: Surprisingly yes! The roller spins freely and smoothly. Despite the destroyed roller surface, the lifter is fine. That is really the source of my confusion.

Bill: Pulling the engine seems to be the best option; unfortunately, I don't have means to remove the engine. A local shop will allow me to rent a bay/lift, but I haven't taken an engine apart in a long time.

1HotRodz: Indeed, the heads must be removed.

shawnaj7731: I'm afraid that my shorthand is not good. What does ttt mean?

 

TTT= To the top, and is a bump of the topic to keep it near the top of the forum.

Also, Good luck with the engine tear down and best wishes that the block is still savable. And as stated, until you clean/replace the oil cooler parts, do not even thinking about dropping any motor back in the car.