OL_DIRTY

I have an EVO9 2L built motor without balance shafts. It has GSC dual valve springs but stock cams (for now).

Since installed the motor has made what I thought was piston slap at about 3k rpm when cold and only when under slight load. The sound seems to just abruptly start then stop or get washed out in engine noise. It cannot be reproduced at idle and it seems to lesson when the engine is hot. That being said.... the other night I was driving next to buddy in a large van and I could still hear the slapping sound resonate off his van even when the engine had been running for an hour. What in the heck can this be?

For reference I have about 10k miles on the built motor. The compression is even across the board at like 110psi and there is no debris in the oil. Performance is very good at about 450whp and decent mileage on E.

I assume a bent valve(s) would show on a compression test or at least show a sub 100psi cylinder. (is there another way)
I assume a bad bearing would have grenaded or at least shown metal flake in 10k miles
I assume a lifter would be present at all RPM and at idle when being reved manually.
I have no idea but can the HD valve springs cause this?

For the sake of my sanity Is there anything else that can be easily checked? Any Mivec related possibilities? I'm guessing its coming from the head but I have been unable to capture the noise with a gopro just yet.

llDemonll

iTrader: (21)

What shop built it? Why not ask them to diagnose it?

OL_DIRTY

The shop is no where near my home so that is a no go. I'm just looking for things to check. Any ideas at all?

barneyb

My car does this a little. I can hear it between shifts especially if I have a window down. Like you, I've been hearing it for a long time - maybe four years. The car runs as good as ever. At idle or revved in neutral - nothing heard. So, something is going to have to get a lot louder, fall off or blow up before I can give you an answer.

barneyb

As I recall, there was a long thread concerning this same complaint that ended about a year ago (so long I never read it all). Several other owners chimed in with the same complaint. Engines were examined and parts replaced all with no result except I think one owner found a loose wrist pin. If you want to test your eyes you could go look for that thread.

4b11slayer

Clutch chatter, ?

TexasLT4

iTrader: (6)

Piston slap maybe? Only happens at 3000ish rpm... Might be a harmonics issue.