4.6 Carbahn Stroker Knocking/Rattle at idle

[tizzyd]

Hi all,

I bought a 2011 M3 that was built by Pfaff in Canada as a GTS replica. It’s an amazing car, but it has a concerning noise I’m trying to figure out, and wanted to turn to the best community I know. It’s making a knocking/rattling at idle, far worse when cold, and pretty much goes away when fully warm. When I add revs it speeds up and then goes away fully above 1500 (or just blends in, can’t really tell). I have driven the car pretty hard and all feels good, I’ve checked the oil and filter and it’s a bit sparkly, but no big chunks in filter or anything. Had blackstone done and copper is high, but the motor only has 2500 miles on it at this point so I’m thinking it could just be break in? This oil was not the break in oil, and was changed when the engine had around 800 miles I think. Carbahn said the noise is not normal, and have been great, but I have yet to figure out what it is.

Here is a video - car is on a lift as it sounds like it’s coming from the bottom end and you can really hear it there. Let me know if anyone has any ideas!

https://youtube.com/shorts/72LqygFwlqE

[DanMpower]

Doesn't Carbahn use forged pistons in their 4.6 stroker builds? I heard you can get piston slap from forged pistons because of their thermal properties, ring clearance is larger making them noisy until fully warmed up. Sounds like it from your description and video.

[tizzyd]

Originally Posted by DanMpower

Doesn't Carbahn use forged pistons in their 4.6 stroker builds? I heard you can get piston slap from forged pistons because of their thermal properties, ring clearance is larger making them noisy until fully warmed up. Sounds like it from your description and video.

I thought the same thing, but carbahn themselves saw the videos and said that doesn’t sound normal. Also really sounds like it’s coming from further down, maybe like main bearing or rod bearing.

[GORDON.M3]

Hate to tell ya but if the Blackstone reported high levels of copper, your mains or rod bearings are on the way to being kaput. The Blackstone UOA never lies. I would also have that motor sent back to Carbanh or whoever is responsible for a proper teardown and diagnosis. That unusual chatter you are hearing is definitely not normal. "Break-in" is not an excuse for high levels of copper in your oil.

[acarr6]

Good ol’ carbahn at it. My gintani 12:1 4.4 has been rock solid!!

Jokes aside, with their warranty and pfaff’s reputation, I wouldn’t worry. If something is wrong it’ll carbahn will sort it.