How Much Tick / Noise Should A Rebuilt M42 Make?

[bmwman91]

So as some of you are aware, I recently installed a very nice, professionally built M42 and had it promptly poop out on me via one stuck exhaust valve (at least that's how it looks, I will look more closely on Saturday when I get the engine out). That is all being taken care of at no cost to me, and I am just curious about what a pristine M42 SHOULD sound like for when I get it back.

When I first fired up the engine, everything seemed to go well to me. There was the expected ~3 seconds of mechanical noise as oil circulated to the places it needed to be and then pretty smooth running. The idle was a little poopy thanks to a vacuum leak. My father and I have a little disagreement going about how much noise should be coming from the engine, and how it should idle. He has built a few motors himself over the years (American V8's & I4's), mostly before I was born, and I generally trust his car advice.

- There WAS some audible ticking coming from the engine as soon as it started and all the other first-start sounds went away. I thought nothing of it because it was certainly no worse than the previous M42 with 220k miles on it. My father's position is that there should have been none at all. I have never heard an M42 that didn't tick, although I have never heard a fresh one with zero miles either.

- Slightly stumbly idle. Before the vacuum leak was fixed, the idle RPMs did sort of "seek" and stumble as many of us here know from having vacuum leaks of their own. At the same time, the idle did feel a little rougher than I remembered, but I sort of assumed that this was from the lighter flywheel and much hotter cams. My dad thinks that this may have been from a valve that was not seating properly (his idea from after the failure).

- Louder exhaust. I chocked this up to the hotter cams and increased displacement. My dad thought that I might have had a small exhaust leak, or maybe that it was the bunked exhaust valve letting exhaust back into the cylinder and up the intake (his idea from after the failure).

Some of this is obviously clouded by confirmation bias. The ticking seems like the only plausible indicator of a bad valve from the get-go, and even then I would not be surprised if a new M42 ticked a little. What say ye, fellow M42 folks?

[DesktopDave]

I'd figure a bit of ticking in a newly rebuilt motor would be acceptable with hydraulic lifters.  The M42 is a noisy motor to start with.  My viewpoint is also biased - just like you, I didn't hear any brand new M42's.

[MikeDE]

Mine ticked loudly for 5-7minutes after starting the first time....then for about another 15minuted but not as loud.  After a test drive I could barely hear it because I was cursing and deaf with rage over my timing case leaking.

Hope that helps......

[tfrain]

Mine ticked loudly for 5-7minutes after starting the first time....then for about another 15minuted but not as loud.  After a test drive I could barely hear it because I was cursing and deaf with rage over my timing case leaking.

Hope that helps......

Haha!  This is great.