Diesel sounding M20 with forged pistons problem

[etagolnik]

My m20 stroker (b28 I think?) sounds funny at cold idle. There is sort of a clanking sound similar to a diesel. I have been informed it may need a valve adjustment, have an exhaust leak or need different oil.

When the engine is warm the sound is gone by the engine but a soft clanging can be still be heard inside the car.

I am running 10w60 Liquimoly oil.

I am wondering if the forged pistons have anything to do with it...Maybe they take time to expand.

I have taken Videos of the cold idle and warm idle.


Cold Idle: https://www.youtube.com/watch?v=7e5x4dVvwxU

Warm Idle: https://www.youtube.com/watch?v=FYXDTfBI-Uc

Input would be appreciated!! Thanks!

[betz]

Yes, forged pistons are noisy when cold and will burn some oil / be noisey on start up. This is due to the different properties of the metal. You can get different materials / coatings that will combat this. Maybe give us info on what type of pistons you bought?

Full disclosure, I did not listen to the video.

But this is one of the reasons I went with stock pistons for my 2.8 build.

[wworm]

just FYI your vids are switched in the first post. No idea what the clacking is. Mine sounded like that and it was a bone stock eta. Not quite as clacky but did sound a more like a diesel than a gas engine lol. Check the valves and see if that helps.

[digger]

yeah forged pistons do that depending which alloy and what clearances are used.

[e30davie]

Your other video suggests it all works quite well:)

Not much help but my Stocko m20 sounds significantly different when cold vs hot. I put it down to being an old engine thing....

[digger]

its always worth rechecking the valve train or trying to chase down the noise as it could be some kind of light interference issue

[ForcedFirebird]

Use a mechanic's stethoscope and probe the rocker cover and outside of the bores. Will tell you in seconds where the noise is from. :)

[etagolnik]

Hey guys! Thanks for all the replies.

- The Pistons are Ross Forged Pistons
- I believe the rods are Eagle forged H beam rods
- Myster-e ported (Bimmerheads?) Head with 272 cam and I believe heavy duty rocker and double valvesprings

I have tried using actual stethoscopes to hear where the noise is coming from and have not been that successful in tracking it down.

I have been told it may be an exhaust leak (doubt it). The exhaust does leak right where the turbo meets the downpipe but I doubt it is the culprit.

I have been told the rockers may need adjusting. Last time I adjusted the rocker lash was before the engine was in the car. So I am hoping that is the issue.

I can also hear a rattle from inside the car, coming from the engine bay when i hold the rpm steady around 1200ish, which could still be the valvetrain.

[etagolnik]

Also, How much oil is supposed to be coming out of that oil rail that passes from the front of the head to the back of the head?

I watched through the oil filler hole as it was running and couldn't see oil spraying out?

[ForcedFirebird]

Doesn't really "spray", it's more like a steady stream/drip. If it's "drop, drop, drop" check oil pressure.

[AWDBOB]

That sounds like good ole piston slap to me. Non coated JE and Ross pistons are known for it. I had an Evo that sounded like a diesel on cold start up. That engine was torn down after 20K hard miles and it looked like brand new but sounded awful.

[ForcedFirebird]

That sounds like good ole piston slap to me. Non coated JE and Ross pistons are known for it. I had an Evo that sounded like a diesel on cold start up. That engine was torn down after 20K hard miles and it looked like brand new but sounded awful.

Nail = Head.



JE, Ross and a few others like to have excessive piston to bore clearance. Great pistons, despite the flack of the internet bosses, but they are loose jugs until ~200°f or so.



Today's alloys are much better, but in all honesty, I have been amazed at how well the hyper alloy OEM Mahle pistons react to abuse, and how tight of a tolerance they allow.

[hasa]

I've heard noisy Venolia's and Wiseco's too. Depends on clearances.

[etagolnik]

- Oil pressure is good. Its about 90psi or so cold and then warm its just under 20psi and rises with rpm.

- Sucks about those pistons...I dont like. The engine is only a few years old. I plan on doing methanol injection and shooting for 400whp. If I warm up the car before beating on it I guess it will be ok if thats normal for those pistons.

- Last night I checked the rocker to valvespring clearance and most of them were larger than spec..I set them all to 0.010". I think the biggest gap I measured before adjusting was 0.016"! I'm interested to see how it sounds/performs now.

- Tonight I plan to button up the valve cover and seal a exhaust leak right after the turbo.

[etagolnik]

So I drove the car today and it still is rattling. Even when its warmed up.

Here is a video. If you listen real good you can make out the rattle.

https://www.youtube.com/watch?v=9WbWsTv2I-g