Hi Guys,
Sorry for the delay in responding to some of the replies on here
Glad it’s continued to be an interesting read for others if nothing else!
Z4M-2006 said:
Hmmm....
This does seem an unusual anomaly..
Looking back through the pictures,if the pistons pics are in order (1-6) then on number 6 piston there does seem 2 points of contact in the valve recess on the crown.
Then bent valves...
Also.... the thread damage in the head where the cam cap bolts is very common on an engine thats had piston/valve contact,effectively at the point of contact the valve tries to push the cam out of its holding point,damaging the threads in the head for the cam cap. I have seen it where the cam will actually snap.
I would suggest that the actually noise you heard at the track was the valves on that cylinder contacting the piston recesses.... Why this would happen is up for debate.
Its been known after timing belt or chain failure with bent valves to run the engine,and rev its cobblers off and it can "straighten" the valve enough for it to seal on its seat again and clear the piston crown and the engine will run fine....Bodged,but fine.
Its all hypothesis of course.... But i must have seen,worked on and rebuilt literally hundreds of engines in my time inc S54's.... and some typical damage occurs after valve/piston contact.
Either way... im glad its fixed,but i doubt the original rebuild was done badly,indeed any issues would have shown up much earlier especially after you have used it hard on the track.
Food for thought
Thanks for your insight – a few responses though;
1. I asked Redish about the pistons – they advised there was no evidence of valve to piston contact or witness marks - certainly to my admittedly untrained eye I can't see any evidence of witness marks. In addition, the engine had run for ~45secs or so including a couple of blips to 2.5k before it was trailered to Redish, and then they started and ran it a few times (after the bottom end investigation) with the clatter present – there would be many hundreds of witness marks from valve to piston contact after that. In my head I can understand how a head with completely vertical valves could to some extent ‘straighten’ any bent valves, but not in one such as the S54 where the valves are angled. I’d be interested to understand how they could be straightened of course – I just can’t reconcile that in my head – especially without pockmarking the piston crown! The other thing to note is the fact that the engine still ran smoothly, no noticeable ‘miss’ with the clattering sound from a lack of compression etc. Sounds like you have plenty of experience in rebuilding engines, so I'd welcome your thoughts

This is the sort of damage I would have expected from a bent valve though: http://www.eatsleeptinker.com/2014/03/06/engine-carnage-revealed/
2. The Cam Cap with the stripped thread was only one of the two retaining threads on Cylinder 1 Exhaust Cam, whereas the Bent Valves were on Cylinder 6 Inlet Cam! I’ve also seen what happens when you get valve to piston contact – a friend of mine managed to snap his cam a while ago – it aint pretty! But I’m certain the damaged thread and bent valves are unconnected insofar as they did not occur from valve to piston contact on track.
3. The other thing to note is that at no point was this noise present whilst actually on track, or indeed coming off the track after cooldown lap and subsequently manoeuvring in the pits. It was only after I switched the engine back on, having been switched off waiting in the queue for 20mins that it started to make the clatter. Up until that point it had been running absolutely spot on!
As you say – so much of this is hypothesis at this point – I’ll never truly know what happened, but I am certainly happy it’s fixed up and ready for more fun and hopefully a few more trackdays now!
abar121 said:
OP, it does look like a case of the motor being buzzed by changing down too early and at too high revs. Witness marks of the valves hitting a piston or more, indicate this.
I'm a little concerned that any shop would have sent you out with cam / follower wear that severe, especially given the anticipated usage. Not what I would expect from a specialist. I'm a bit confused with the drawn out diagnosis, given that Mr Vanos has heard similar many times in the past and was contacted early in the diagnosis process.
I have no problem with cars being correctly driven on track, but any potential issues will for exposed for sure.
Could you point out the witness marks to me – call me thick but I can’t make any out, certainly none indicative of a proper ‘buzzed’ shift on track! I can say pretty confidently that I didn’t buzz it on track, so again rather confusing!
In relation to the wear – I asked Mr Vanos to do my Vanos and Timing chain at a friend’s unit, so whilst he commented that my top end was certainly well worn, I am quite comfortable that he had no burden of responsibility in relation to the top end of my engine – he certainly didn’t ‘let it leave his shop’ - he wasn't there to do any work on it aside from doing valve clearances, and didn't have any parts or tools to undertake any work on the Cams or Followers. As per the write-up, after the trackday, I did get input from Mr. Vanos, who’s immediate response was that he’d be prepared to bet his car that it was a flattened follower making the noise. However for various reasons (partly related to the cost of getting the car to him, lead-time for him to start the work, and the fact that I foolishly still believed somehow that it was bottom end related) I ended up getting taking the car to Redish who had the capacity to undertake some initial diagnosis more swiftly. In retrospect, as Mr Vanos had quoted to do the follower and cam replacement without removing the head, therefore I’m glad that I went with Redish who took the head off. If they had not, I would never have discovered the bent valves, so potentially could have ended up thousands of pounds into it, with the clatter still present.
BMWZ4MC said:
No worrys, I’ve been pretty swamped with my new found responsibilities!
I’m about to have an inspection service so I’ll make sure that the condition of the followers is noted.
The centre caps I lost here were OEM, so I’m not sure that is a guarantee!
The ‘item’ looks great on the website. I hope it’s a straightforward swap when the time comes - I’ll add pics here or start a separate thread once it’s fitted and tested.
Very exciting, I bet you're busier now than you've ever been!!

Well that settles it - I'll grab a couple of decent quality ebay ones - and will try and remember to remove them before going on track next! :lol:
Very exciting about the 'item' - look forward to updates via whatsapp - and definitely get a thread up of the install! I'm sure the process will be broadly similar to my experience, so if you need any help as you go drop me a message
