Originally Posted by
bennyfizzle
Allow me to preface this with a little background info. This is a ~90k S52, began pressurizing cooling system last June and I did not have the time or resources to repair at the time so it sat until early this year. Brought the assembled head (cams in) to the machine shop to be checked, cleaned, and decided to go with a valve job while I was at it. It should be noted that no significant amount of material was taken off the head, it was no warped or cracked, and they merely surfaced it.
After I got the head back from the machine shop, I timed the motor in and rotated by hand. Motor hung up around 270 degrees into the first rotation, so I backed it back to TDC, verified timing once again, reassembled and tried turning the motor over by hand yet again. Once more I was met with resistance in the same spot. I applied a bit more pressure, heard a pop, but then the motor turned over nicely by hand. I know that sounds a bit funky, but everything in the head looked fine, turned over nicely by hand with no weird spots, and after buttoning everything up the first start went well.
This past Friday I finished the car, got the cooling system bled and got the car up to temp. There was a little bit of typical hydraulic lifter ticking that went away in a minute or two, and the head was quiet. Yesterday I fired the car up to put some street miles on it, still quiet, and left my shop. I stopped at a gas station about a 1/4 mile away and put some fresh fuel in it, and as I was leaving a loud tick developed. No stumbling or hesitation, no other symptoms really, just an alarmingly loud ticking. I hopped out, and tried to track down the tick. It seems to be coming from the head, though I'm having trouble pinpointing where exactly. Here's a video I took shortly after:
Since then, I've put about 50 miles of mixed driving on the car, even some 'spirited sack-busting'. The motor feels fantastic, makes smooth, consistent power throughout the range. But still, this loud ticking persists.
Additional details:
Oil pressure is great, and exactly as it was before the hg job/vanos rebuild.
The check-valve in the head is in place
Using Rotella T6 5w-40 oil
I've tried the 'bleeding procedure' of holding revs at 3k with no load for one and three minute intervals with no change in tone or frequency.
As you can see in the video, the sound is dependent only on speed of the motor and not load.
I'll be doing a compression test and pulling the valve cover soon to check for obvious signs of failure. After speaking with the machine shop and describing this scenario, they think I may have bent a valve when I was turning the motor over by hand. I doubt highly that it would take as little force as I applied turning the motor over to bend a valve, and I can't see how that would be possible. I followed guides on the subject of timing these motors exactly, and the motor runs perfectly aside from the tick. I asked them how the lifters were handled, and they said the only thing they would have done is drain the oil from the lifters to make sure a valve wasn't being held open (??) and cleaning them. Two other M50 heads were done within the same week as mine at the same shop (friends of mine), and have no problems or lifter tick.
I'm posting merely to ask for any applicable experience in the matter, and maybe some words of advice/past experience. If nothing else feel free to post about how loud my head is.
Thanks,
Ben
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