This Might Be A Tough One
 

Hey guys
Ive had this problem twice now.
For some reason the engine keeps bending a valve on cylinder 2. (Intake- the center valve in between the 2)
I had this problem occur before and we took the head off and replaced the valve.
Timing was done by camshaft markings and using the camshaft lock bar. (big holes pointing at each other)
We recently finished replacing the valve and made sure everything was in place.
We hand cranked the engine with timing all set and each revolution was clear of any dings. Started the car last night and it ran perfect. Test drove it today and it drove perfect...until we drove uphill on the way home I heard a ding, pulled into the driveway and the dinging would sound and stop continuously. We also added new lifters.
After the dings it started to run shaky and started sounding like a misfire. We did a compression test and the car bent the new valve on cylinder #2 again!!
Any suggestions or past experiences you can relate to feel free to let it out.
Before my car ever bent a valve it ran so good! ever since the bent valve my car hasn't been the same. Its keeps bending valves.

98 Audi A4 Quattro 2.8L V6 30v Manual

Did you also replace the piston on that cylinder?

No I didn't think I had to. Nothing seems to be wrong with the piston.
What would indicate that the piston needs replacement?

You dont need to replace the piston. Iv revalved all these 5v engines plenty of times with good results. Tear it down, maybe a keeper didnt get seated right or somethings wrong with the guide. You could put a different head on it if you had to. Only time we have seen this happen is when reusing lifters on the bent valves.

Well I did notice something yesterday. Before I went to work I checked
out the head and I had it sitting outside in the sunlight. With the old valve
out and the new one in I noticed sunlight seeping in through the intake holes
revealing that cylinder #2 has always been leaking compression no matter if
we threw in a new or old valve it was always going to leak. SO we got to work on that and used a special stone on a bit made specially for bad seats
for valves and sure enough we had sealed up the gap and the valve was now
sitting entirely on the head. We did a leak test and no leak through. Now
that's one issue fixed but tomorrow I'm planning on getting a new timing belt because its never been replaced and I was told the belt stretches over
time and that might have caused it to skip a tooth.
I doubt the guide is damaged because the valve can be pushed in just by
slapping it with your finger. I understand that if the guide was damaged
the valve would slow upon closing. The first time around we reused the
lifters, this time we bought all new ones and same result occured.

So you replaced the valve without doing the guide?

Or the 16 year old timing belt apparently!

Why would you....if its within tolerance still why would you change it?

I've done plenty of valve replacements and never had to replace a guide.

That's more concerning than the guide...