Head replacement due to damaged valves

[Troller]

Hello, I am new to the forum and have not found my answer in existing posts. I have an 04 Aveo with 102,000 miles and just had the timing belt idler pulley fail. Its is on its second timing belt, which was still in good shape. All of my exaust valves are bent and several of the intake vales are damaged. I was planning on purchasing a rebuilt head from EBAY for $350, replacing the water pump and all the timing belt components. The pistons have a few nicks, but look pretty good. If i have to get into the lower end, I will probably junk the car.

Has anyone had the lower end fail after rebuilding or replacing the head only after a timing belt failure?

Any advice would be appreciated.

Thank you

[krazy_85]

I had the belt fail on me and all exhaust valves smashed into the head while driving. The block should be ok. If the pistons look good and if you can turn the crank by hand (while in neutral) and see the pistons move your block should be ok. I had taken my head in to be rebuilt, it cost $550 for me. I put it all back together and it ran fine but the head gasket kinda moved on me when installing after the belt fail causing an oil leak by the exhaust manifold. Now I redone the head gasket and it runs like the day I got it. Hope this helps.

[Troller]

Thanks for the info. How much damage did you have to your pistons?

[jimzdat]

I bought ours with a similar issue - 16 for 16 on bent valves. Also cracked most of the valve guides.
I bought all new valves and guides, and did the install myself; so saved a lot on labor that way.

As far as the bottom end goes, there was very little damage to the pistons - due to the angle of the valves, they almost hit the piston directly on the face, and then bend the valve stem. I used a jewelers file to clean up a couple small nicks, and then reassembled. Have put a few thousand miles on the car since then with no issues - and since my kid just turned 16, it'll be his car as soon as he gets his license (gotta pass driver's ed....)

[Troller]

Hopefully this photo attached, this is the extent of my piston damage.

[jimzdat]

Hate to be the bearer of bad news, but I wouldn't run those pistons on a dare - the damage at the top of the photo is livable, but the impact on the bottom of the photo is a deal breaker. With the valves impacting the piston that close to the edge, there's too great a risk that it has deformed the groove holding the top compression ring, if not breaking the ring completely.
Even if it didn't damage the ring groove, the deformation at the edge of the piston will cause hot spots during normal operation - the same will hold true of the upper nicks, but there's more metal around them to dissipate the heat - at the edge, it can cause cracking of the piston.


http://image.hotrod.com/f/36260748+w...ng_package.jpg

Generic piston picture; not sure how close to the top of the piston the top groove is on the 1.6.....

Some others may weigh in, but I'm guessing the response will be similar - I've been working on cars for 35 years now, have my own shop and ASE cert, so I'd like to think I may have a clue.

Honestly, with that low a mileage, as long as the body is in good shape; I'd be looking for a used motor, or replacing pistons - if you find a used motor, just put a new timing belt on and go from there (along with the other important stuff like a water pump, etc.)

[Troller]

I could be wrong but from what I have researched, the indents on those pistons are factory. The portion of the piston where the carbon was rubbed off is where the valves hit. If you google 2004 chevy aveo piston, you can find an image of a factory new piston with those marks. My only guess is they were placed in the pistons to add clearance for the valves. Do you still think the motor is done if those marks are factory?

[jimzdat]

It's been a while since I had the head off, so I may have misspoke- if those are the oem clearance notches ( looked at rockauto, see what you meant), then as long as there's no additionall damage, you should be able to move forward with no issues.

Sorry about that, last couple of engines I've pulled heads on were flat top pistons, and I totally neglected the fact that it may have been clearanced.

I'd look closely to make sure no displaced metal, and if it's clear, go for reassembly

[Troller]

Thanks for the info, I am by no means a mechanic. I am going to go with a head on EBAY from cylinder heads international. They are $350 with shipping and have good reviews. I think the time I will save messing with it my self is well worth their price. I have been turning the engine over with a ratchet and it feels smooth. Hopefully everything down there will last for another 100K.

[TurboElk]

Yes those are valve reliefs... totally normal.