chances of cylinder head destroyed in a timing failure?

[1Gina2G]

title basically says it all. I know it's a worst case scenario but possible to have your head destroyed in the event of a timing failure where some valves atleast get bent, but it looks like most of the time the engine gets cut off right away and most people end up reusing the original head.

how often does a head get completley destroyed when this happens, anyway of telling? I'd imagine only someone whos done alot of head jobs for these cars would know. I also understand that the block can receive damage by scored walls if peices come loose and fall into the cylinders.

 

[3kgt2nv]

chances are better that something gets tweaked than you escape unharmed.

 

[Joethefallen23]

9/10 guys will bend valves. There's always that one guy that catches a break but don't expect it to happen. I personally haven't seen damage to the point where a head can't be used. Is it possible? Sure.

 

[1Gina2G]

I understand that in the event of a timing failure / jump you're basically guaranteed to bend valves, even if you shut off quickly, or probably atleast bend some valves slightly. some people have said they actually ended up with no bent valves by chance after a failure but pure luck.

so the heads going to come off basically in my eyes, after a leak down test or 2 but nothing happend to me i'm j.w how often the head castings can become junked through just a failure.

 

[Joethefallen23]

I understand that in the event of a timing failure / jump you're basically guaranteed to bend valves, even if you shut off quickly, or probably atleast bend some valves slightly. some people have said they actually ended up with no bent valves by chance after a failure but pure luck.

so the heads going to come off basically in my eyes, after a leak down test or 2 but nothing happend to me i'm j.w how often the head castings can become junked through just a failure.

99/100 times the casting itself will have no damage. There's always that one person though that will trash it out of pure bad luck. Luck is certainly a factor no matter whichi way you look at it. I've seen a cam snap in half once on a timing failure but it was do to a casting flaw on the cam itself. It couldn't take the impact of the valves on the piston.

 

[BogusSVO]

It all depends on your definition of "junk"

I can fix a head that you call junk. Short of the head being cracked in half. But there is a point where you have to look at it if it is cost feesable to fix.

I would bet over half the heads bolted to a 4G63 are technically junk, for the simple reason the head is milled past factory specs.

Here is a head that I rebuilt, It broke a SuperTech Valve when the timing belt became loose.
http://www.dsmtuners.com/forums/cylinder-head-short-block/439824-4g63-dropped-valve-head-repair.html

A couple of 4G63 heads that broke a stock valve when the belt failed.

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[issac712tsi]

Here's my little story, when I did my 1st ever timing job, and didn't use a new tensioner, being a noob I cranked the car,(didn't start) and bent my exhaust valves, and cracked the guides. Head was fine tho.