Audi 2.5 5 cyl head problems

Hey all, recently have encountered some pretty bad head issues with my TTRS 2.5 built motor head.

During a dyno session on only 5psi of boost, we turned the motor to only 7400rpm. The pull went very smoothly, but as the engine came to idle, we heard a very loud knocking noise. Diagnosing it as an issue with the head itself, I've since pulled the cams out to find 3 collapsed lifters out of the 20.

The cams are exhibiting abnormal wear, they are brand new, only 1000kms. The peaks are showing chatter, could this be caused by excessive lash having the lobe smack up against the roller? They were installed with the built motor, so it's a fresh setup with genuine Audi brand new hydraulic lifters and brand new roller rocker arms.

Even the lobes that don't show abnormal wear, the rollers are looking a little weird.

I believe there are multiple issues going on at once, however what could cause 3 new lifters to collapse, and for almost all lobes to have some sort of chatter near the peak? There is adequate clearance between the stem seal and the retainer, I am running 10w40 oil and oil pressure above 2000rpm is a steady 75psi.

Could I have not enough preload on the lobes causing chatter? Should I shim the lifters? Did I just get unlucky with the 3 lifters failing?

The motor has also been labelled as "noisy" by the tuner while setting up the knock sensors during pulls with random spikes in knock signal, even though the motor is not knocking at all, could this be a lifter coming down during higher rpm with excessive lash?

I'm at a loss, I have brand new lifters and rockers coming, the cams are getting repaired, I really do not want this to happen again. Any opinions?

Bear in mind I'm not that familiar with the engine, so more general comments.

My first thought was potential valve float as, depending on the camshaft and springs, this can be an issue with damage similar to what you're reporting. I can't find the "official" 'red-line', but mose pulls seem to stop at 7k, and the few that went higher dropped off steeply after that point, which sometimes indicates loss of valve control - even OEM parts will often tolerate only a small increase in rpm, as the forces involved increase by the square of the rpm increase.

Not sure what you mean by "lash", which I normally take as valve clearance, hydraulics should have no 'lash', rather a degree of 'pre-load'.

However, looking at the pictures, I am also wondering if it's caused by debris from the oil-ways making it's way into the oil feeds and being chewed up in between the cam(s) and rollers? If so, it may potentially cause the lifters to fail, too.

Hi Gord,

Thank you so much for your reply, I knew I forgot to mention something.

The head is a full race spec built head, the official redline is about 6900rpm, I plan on revving it out to 8500+.

I'm using Supertech springs with oversized valves, which at only 5psi, it is extremely unlikely to be valve float so early on..

I can appreciate that there may have been some debris when I was assembling the motor, however I was extremely meticulous, but it's never impossible..

When I say lash, I'm referring to the excessive clearance between the roller on the rocker and the cam lobe once the lifter starts to pump down.

I have the cams with the machinist so he can fix the damage, and I have a new set of lifters and rockers, but I really don't want to go through this issue again..

I am making a few changes, I am changing to a different oil, even though the other oil is extremely good, I want to rule out any possibilities and switch to Lucas Racing Only 10w40. I am also having the machinist check the cams for straightness and potentially balance them also, I know balancing isn't required, but this has put a bad taste in my mouth, and I may have the lifters shimmed to have a bit more preload on the roller.

Does any of this sound excessive or unjustified?

Again, I'm not that familiar with the engine, but there should be numerous forums with more information - it seems to be quite popular in the US, for example.

I missed the reference to getting the camshafts "repaired", earlier. You may be better off writing them off, as re-grinding will remove the treated surface layer and reduce the base circle - the former may increase wear and the latter will affect the base circle and affect the pre-load/clearance and geometry. On that, you could try contacting the cam' manufacturer's tech' forum, to see what input they have on this?

Hi, not sure if they will fit the TTRS engine but i have used the ferrea lifter shims on my build (Audi rs4 v8) just to help control the lifters, with increasing the rpm there could be a possibility of locking out the lifter then that will damage it then cause it to collapse,

just a thought 👍🏼.