Breaking valves

[Baal]

Well last wekeend my rally Clio 172 broke the valves in one piston, we were very puzzled why that happened since it was low revs and the belt was in good conditions so we had no idea.

So today my mechanic calls me telling me that the valves (of the same piston) broke again, apparently the car was making a weird grinding noise at idle, when he revved it up a bit the sound went away, so my only theory is that the VVT pulley is damaged and is switching the timing and the pistons are hitting the valves.

I have the 5502428 catcams which are pretty mild and afaik can perfectly run on standard springs, and since its happening at low revs it just doesnt sound right, any ideas?

 

[Baal]

extra info:

The cambelt is new (changed after the first valve failure), also the head is very slightly milled, i think .010"

 

[Fred@BTM]

the valves are sometimes weak, you do have the cam timing 100% correct don't you?

 

[Baal]

yes timing is correct, took the head to a specialist to see if theres something wrong with the guides but everything seems fine, we put in 4 new valves and 4 new springs (in case one was soft or something) i might change the VVT cam too.

What i want to know is if its possible that a failing VVT cam can somehow change the timing that there is interference or even in the worst case scenario it would only cause a rough idle.

 

[Baal]

guys?

 

[Fred@BTM]

have you checked the VVT pulley for play?

 

[Andyman]

PM sent