Valve adjustment and bad engine mounts

[jhu321]

Adding to the experience. Don’t know if mine experience is universal. I just bought a 100k mile e46 m3 coupe. The engine had a little valve tick when I got it so I did an adjustment. Tick got better and didn’t think anything of it.

fast forward a few weeks later while prepping the car for autocross I decided to refresh a few things. Injectors, fuel regulator, filter, pump, intake etc. diff fluid. typical 100k mile deferred maintenance stuff.

after the car was put back together the tick turned into a very sharp metallic tint tiny tint that sounded from the back of the engine bay / bell housing / under passenger seat.

since I just redid fuel system. I thought it was the regulator bouncing cuz of the new injectors ticking. Didn’t think much of it.

after autocross the sound for even louder so I started diagnosing. I chased up and down the fuel system. Disabled injectors 1 by 1 by disconnecting coil.

found the sound to be not in the fuel system with a stethoscope. I hear it in the exhaust pipes and bell housing as well as only the valve cover bolt closest to cylinder 6 exhaust.

after chasing down and tracking the frequency tied to rpm I figured this is cam shaft related at 7.5 hz at 1000 rpm’s.

so I opened up valve cover to check clearance.

what I found was the exhaust side was completely out of spec. Something that I just did within spec a few weeks ago everything was off.

starting from cylinder 1 through 6. Everything needed bigger shims increasing.

Cylinder 6 went from 2.18 to 2.62!!! A good .4mm increase which is almost unheard of.

Cylinder 1 went from 2.28 to 2.32.

net net the only thing I can think of is the engine mount changes the geometry on an old engine. This is something I’ve not found anyone report before so adding to the internet memory and hopefully this’ll help someone at 2am pulling their hair out.

Net net. Do your mounts before doing valve adjustment. Or after you change your mounts revisit your valve adjustment.

Now my engine sounds like a very healthy s54.

[Barracooda]

I just can't see how this could possibly be related, the head would have to warp or deflect. Are you sure the engine wasn't warm during one check and cold during the other?

[digger]

lol what

[Flow]

I agree with the others. If you engine warps because of engine mounts then there is something else seriously wrong. There is no way those 2 things are related.

[Shonky]

+1 correlation does not equal causation

[jhu321]

I just can't see how this could possibly be related, the head would have to warp or deflect. Are you sure the engine wasn't warm during one check and cold during the other?

Im the first to say yeah. This is crazy. I didnt think so either. But i have no other explanation of how the valve clearance on the exhaust aide went off by that much.

lintake side was perfect.

exhaust side every cylinder was off. I had to increase by .04 on cylinder 1 and continue with larger and larger every cylinder by the time i got to 6 it was .44 difference.

Engine was cold for valve adjustment both times. I wouldn’t want to be touching a hot or even warm engine anyway.

Ive done a few valve adjustments for s54 so i kinda known the drill. And this engine i had a buddy lf mine help me and he witnessed the feeler guage test. He saw and confirmed he saw i validated the clearances 2x originally.

when I opened it up today it was just crazy off. I couldnt believe it myself. The incremental gap going towards the back of the engine points to some geometry change but in all honesty Im skeptical about it myselt.

like if j was .04 off and needed to go up a size of shim sure maybe I messed up on a valve. This is every cylinder ajd cylinder 6 was .44 off. I have no other explanation, it goes against everything i know and understand as well.

the only thing i can think of that could have changed that much was the engine mounts. There is a noticeable difference in alignment of the exhaust berween the good and bad engine moiunts. With the bad engine points the entire exhaust was pushing up on the engine i know this because the rubber mounts were completely squished to thepoint where the mid pipe was pretty much just in contact with the chassis.

after the engine mount was fized the exhaust was hanging loose as it shoulvr been.

im not saying this is the answer. Im just saying this is what j experienced hence dont known if applies to anyoje else. My ownership of this car is 6 weeks. I have no other history with this car so i may have other issues for all i know but i cant explain such a drastic shitt in clearance with less than 500 miles of driving. Like it just ahouldnt be possible,

[Shonky]

OK then, why was 1 cylinder off by 10x the others? What you're suggesting is that engine mounts are essentially warping the head or something but only for one cylinder. Really does not compute. And just by supporting the block.

The 0.04mm variance is basically the tolerance allowed (1.5 thou) so I don't really buy that.

I don't know how clearance varies across all engines but 2.62mm sems high in my experience.

[JakeM346]

You should check the timing.
Maybe slight fault leading to contact that then slightly bent the valves leading to them not closing the same. In this regard just do a compression test.
Last Cylinder is always most effected by heat so yeah maybe expanded the most and got slightly hit.
So yeah just do a compression test…

[George Hill]

I have run the valves on 100's of S54 engines and I have never seen a shim past 2.5x and only and handful in the 2.4x. And then considering this scenario I just don't see it being a thing that I feel could happen naturally. I would double check your lash.