I’m looking at possibly buying a very clean 10 xfr with 74k. The dealer disclosed that the engine had recently been repaired for a bent valve. I tried to get info from the repair shop with no success. The dealer reported that the motor work just included the head removed. I’m concerned that the block and bottom components are victims of abuse and are prone to failure.... probably due to turning or nitrous or both.
How likely is the bent valve to have occurred on a non modified engine and how likely is the bottom end to be vulnerable to future failure??thanks in advance.

 

Why risk it. It doesn't sound great. These engines suffer from timing chain wear and perhaps it got too slack; oil starvation etc. Whatever the cause who knows what other damage was done

There are plenty of them around - quick search and I can see at least a dozen 2010/2011 XFR for sale. And don't forget the V8 Supercharged in those years is basically the same car without a few bits of bodywork bling, and even more of those around. So I'd look elsewhere for a well looked after one

Also a number of us on here, so you might get lucky with someone looking to sell!

 

Bent valves on these engines are generally caused by timing chain issues. Stretched chains allow the valves to overlap and hit the pistons. If that was the issue walk away, if the timing chains and guides were not replaced (you would hear chain noise if that was so bad that it did that, Listen to the engine, open the oil fill cap and press on the chain there, there should be NO slack


I have repalced vavles in oher motors (Saab 9000) thatg hit the piston heads with no issues due to a missed shift (but I checked compression to be sure there were not micro cracks.

 

Yep, I'm with BritCars here - not like there's a shortage of these cars available.

I can think of three ways the valve bent:

• Internal failure of valve train (i.e. manufacturing tolerance issue with valve keepers or similar) causing valve to drop and make contact with the piston - pretty unlikely
• Debris making its way through or from the supercharger and into the engine, which makes contact with the valve and the piston - a large enough piece of debris to do this is almost impossible
• Slipped timing chain causing valves to open at incorrect point and make contact with the piston - most likely in my mind, given the known issues with the earlier timing chain/tensioner setup which BritCars mentioned

Note that with all three options above (and presumably any others I've missed) the valve has made contact with the piston - but if they only sent the head away this would suggest that they've left an (at best) defaced piston in the block with the idea that they can just clean the head up, etc.

Unless it's a very good price, and you also can get confirmation they've updated the timing chain gear with the redesigned stuff (and if you were swapping out the head, why wouldn't you), I'd steer well clear.