Engine noise after rebuild

[catech11]

https://www.youtube.com/watch?v=Vb_9f2QtgG4&list=UUSknnTQzlWVLGbWvHhpv59g&spfreload=10

Link to video of engine noise after rebuild.
1989 325i M20b25 with e36 injectors.

The car idles fine but the engine noise is heard at about 1500 rpm or when you let off the throttle. The noise goes away when driving at higher rpms.

Not sure what the problem is, I'm sure someone has an idea of what this could be.

[MR 325]

Kinda sounds like rod knock to me. What was done during the rebuild?

[catech11]

New bearings, new rings, all gaskets new, crank polished, head resurfaced, Valves reseated, Re honed, crankscraper, refreshed Pistons, new belts, new clutch...

[efficient]

Maybe you didn't adjust the valves correctly. I'd try that 1st then I'd assume it's rod knock. Good luck

[IronFreak]

did you plastigauge the crank after having it polished? Like said about, your rod bearings might be sloppy.

[catech11]

Doesn't sound like its the valves to me valves are more of a ticking. F$&@!!! I thought it sounded like rod knock was hoping someone said it was something different. I did not plasti gauge it. It was more of a clean rather than take material off. It was a crank I picked up from cabriolet.

[Quinthirty]

1989 325i M20b25 with e36 injectors.

Are you on stock ECU chip? The injectors will knock on stock chip.

[DesertBMW]

the engine noise is heard at about 1500 rpm or when you let off the throttle. The noise goes away when driving at higher rpms.
.

That is a symptom of slightly too much clearance in rod bearing or piston wrist pin bearing. at 1500 rpm and when decelerating there is a great amount of vacuum working the piston thus the loudest noise. Higher RPM means more throttle less vacuum and more oil pressure.

[catech11]

Are you on stock ECU chip? The injectors will knock on stock chip.

Yes its on a stock chip, from what I've read the ecu will adapt within several miles and adjust the fuel to fit the injectors because there is not a huge difference in them

[catech11]

That is a symptom of slightly too much clearance in rod bearing or piston wrist pin bearing. at 1500 rpm and when decelerating there is a great amount of vacuum working the piston thus the loudest noise. Higher RPM means more throttle less vacuum and more oil pressure.

Thanks for those details I'm 99% sure thats what it is now, its at BTM Motorwerks right now, was running out of time decided to just take it in to the shop

[MR 325]

The injectors will knock on stock chip.

[EatsHondas]

That's rod knock bro, hate to be the bearer of shitty news, but I've been there and done that. It sucks.

[catech11]

So the shop just called they checked all the bearing clearances and they are all good. They think that the pistons are too loose in the bores. All I had the machine shop do was rehone. They say the only other thing I can do if its the pistons slapping around is rebore and get custom pistons. I would be much better off getting a different motor...what do you guys think could it even be the pistons I'm hesitant to believe they are that loose but that's really the only other thing it can be

[catech11]

Well no one wins the guessing game this time, it was a wrist pin. Specifically one with no clip which I failed to see during assembly. The wrist pin wiggles loose and put a nice score in my fresh cylinder walls, such great luck...