Need advice on chasing down a rattle on my m20.

[gnmzl]

This car keeps kicking my ass and decided to ask for some forum help not only in my build thread.

I need to pinpoint this stupid rattle/knock in the engine I've been chasing for the past month an a half. I don't drive the car anymore because of it, only start it and warm it up once in a while after I change something.
Engine is a freshly built 3.0 m20, everything I could afford is brand new. It has covered over 3000 kms now and just recently developed a noise that wasn't there.
Here are some of the components built in, in case anyone can share some known issues with them

Bottom end

M20b27 1985 block
Low mileage m54b30 crank and rods
Low mileage m54b25 pistons, milled down for valve relief and CR
Kolbenschmidt rings
Brand new M21 oil pump
IE crank scraper dremeled to fit the m54 crank and rods
IE windage tray

Head
Slightly ported and polished 885 head
M40 valves cut and polished to match the m20 valve height
All new valve guides and seats (3 angle job on the seats)
Dbilas 292^o Camshaft with 11.2 mm lift (2mm clearance to piston, measured with clay prior assembly)
Schrick dual valve springs
Vac Motorsports spring perches/retainers (are they called perches?)
Brand new rocker shafts
IE HD rockers
Brand new OEM eccentrics and hardware for them
Brand new oil tube
Nuke performance cam wheel (checked it for clearance to the bolts for the cam shaft seal - it clears)

Here are the symptoms and what I've done so far:

Symptoms:

Rattle when engine running, rpm dependent, not movement or under load dependent. It is there even if cold started (cooled down overnight). NOT there when I start the car after 4 or more days of not driving it, but by the time I switch off the lights in the garage, close the door and lock it, get back into the car, the rattle is already there - quiet, but already there. It gets worse when the engine reaches operating temperature. It got progressively worse/louder over the course of about 10 days of driving after the last track day. I can hear it pronounced listening from the top of the engine, less pronounced from the bottom with the car on the lift, but still loud enough.
On that trackday the oil DID get to the 150^oC mark briefly, which is about 300^oF, but the oil is now changed. Water temp never got over the middle mark.
Oil pressure is 1.3-1.4 bar (18.8 psi - 20.3 psi) when idling on warmed up engine and always has been.

The engine DOES have a windage tray and crank scraper.
No noticeable power loss ( nor gains as well for that matter :D )

What I've done so far:

Oil change (flushed the oil cooler too) - didn't work
Rocker arm eccentric to valve stem clearance adjustment TWICE - second time was on the engine 10 days not started, did them 0.25 - no change at all
Inspected the oil tube over the rockers - clean, oil passes through, isn't low enough for the rockers to hit it.
Checked as best as I could for rocker arm and eccentric premature wear (everything is brand new) - no visual issues
Verified following twice: timing, bolt on cam sprocket, jeesus bolt and crank sprocket too - nothing out of order
Cam sensor doesn't hit the trigger in place of the distributor.
Cam belt tight enough, not slapping about
Started engine without accessories belt - no change
Unplugged coil connectors one by one while engine running to listen if the noise would change - no change
Pressed gently against the clutch on warmed up engine - didn't feel it through the pedal.
Listening with a screwdriver from the top I can hear it between cyl 2 and cyl 3, when listening from the bottom on the pan - almost everywhere. Not on the block though.
Pulled the plugs, in order of appearance








What I still haven't done yet:

Compression test, but did one before this rattle emerged - average of 210 psi across all cylinders on a warm engine.
Check the drive pulley on the oil drive shaft (it is a brand new unit, the solid one, not stamped steel one)
Pull the pan and check bearing caps.

A short video:

https://vimeo.com/360510585

So, if anyone has any input for me, highly appreciated.
I'm waiting on a tiny camera with an LED to stuff into the cylinders right now. But would like to know if there is anything else I can check before pulling the pan off. Really don't want to do that, figured someone may have had similar experiences.

Help, please

[tim88325is]

Does it go away when you push in the clutch pedal while not moving at idle?

https://www.r3vlimited.com/board/forum/e30-technical-forums/engine-drivetrain/transmission-driveline/263807-transmission-rattle-at-idle-with-clutch-out

[digger]

Did noise start after the high oil temp event?

[gnmzl]

Does it go away when you push in the clutch pedal while not moving at idle?

https://www.r3vlimited.com/board/for...ith-clutch-out

No, I did this test a while ago and didn't notice any difference at all.

Did noise start after the high oil temp event?

The noise started shortly after the high temp event,next day to be exact and got progressively worse over the next 10 days.

New development:

Yesterday a member on here (zoomer) bought a small LED USB camera and called me immediately, he picked it up in my area. We went ahead and stuffed it into the cylinders and sure enough - valve to piston contact.
We took the timing covers off and did find the belt to be a bit loose, but the timing marks still line up perfectly. Adjusted the tensioner, belt is now as tight as it should be - marks still line up perfectly good.
Here comes the weird part. We rotated the nuke to retard the cam about 4 degrees, assembled all the stuff and started the car for about 3 seconds. Noise was LOUDER and now with higher frequency. Returned the nuke gear to zero, started again - a bit better but still there.

Now the question is - why did this engine cover over 3000 kms without making valve to piston contact and start doing it after a hot oil event? Both things seem to not be connected. Is it possible that the belt stretches under any load, even idling and causing the valve-piston contact, but returning to normal when engine is inop? That seems sci-fi to me, but has anyone encountered that?

I really don't want to reassemble the engine without finding the cause of that.

Another thing that comes to mind - the woodruf key on the crank sproket potentially could have failed, causing the timing mark to align, but the crank would be on the incorrect position.

What I intend to do next is rotate the cam gear in the opposite direction, start briefly and if it doesn't knock/rattle, I'll check compression numbers and take it from there. Definitely will check the woodruf key on the crank sprocket, but if anyone has some other pointers, would be happy to read them.

Thanks for the input, tim88325is and digger.

[digger]

Did you check P to V during assembly?

which valve was contacting ex or in? Advancing adds ex clearance and subtracts inlet clearance

[gnmzl]

Yes, I checked during assembly, measured the clay while on the piston, it was about 2.2 mm. Only picture I have though



I saw marks for inlet, but the camera wouldn't wiggle enough for me to check the exhausts :(
Only thing I can think of - me being stupid and actually advancing the engine instead of retarding it. That's quite possible and only logical explanation.

[gnmzl]

Plot twist:
Turns out I didn't retard the engine, but myself.

Using my memory of yesterday eve and the below link as reference, I was a dumbass and advanced the engine instead of retarding it.

https://help.summitracing.com/app/answers/detail/a_id/4706/~/advancing-%2F-retarding-a-camshaft

Attached is an image of what I think I did.

Guess joke is on me. Hopefully my stupidity will help someone in the future.

[digger]

in fairness its not indicated on the nuke gear which way to adv and which to retard. in anycase as yuo'll be aware you probably bent the valves..

[roguetoaster]

Turns out I didn't retard the engine, but myself.

Sig worthy solution.

[gnmzl]

in fairness its not indicated on the nuke gear which way to adv and which to retard. in anycase as yuo'll be aware you probably bent the valves..

I don't see how they wouldn't have bent too. And yes, it's not indicated, that's why google provided a picture of another m20 cam gear, which is obviously wrongly indicated. Still, it's my fault for not making sure I do the right thing. Once I'm back from vacation, I'll do a leak down test and a compression test (again) and provide closure for the thread's sake.
Thanks for jumpstarting my brain, digger

Sig worthy solution.

Permission for usage granted :D

[digger]

I do leakdown rather than compression test

[gnmzl]

Time for an update, I had exactly one month to chase down this devil.
Here's a recap of what happened, with the help of a friend. Shoutout to member zoomer.

First and foremost I did a leakdown test, I had to buy the tool to do it. I did it twice for each cylinder just to be sure. All were below 15% leakage, which I hardly could believe, yet again the engine ran under 5 seconds with the advanced nuke gear. So the test showed all valves are seating good enough.
Next order of business was taking off the oil pan - what a pain with a scraper and a baffle.
Oil looked mint, not even the slightest debri in it, when I filtered it through the finest painter's filter.
No heat discoloration either on rods or crank, no play in any rod or whatever I could reach in there.
There was e tiny little smidge on the scraper, where a rod bolt had touched it ever so lightly. So small, the camera wouldn't catch it. Ok, so off with the scraper. Assembled everything, poured the oil back in and fired it up. Still clacking, right from the start, same noise again temperature independent but RPM dependent, sounds like only one element is hitting another once per revolution.
Next up - discovered a tiny play in the crank sprocket, so small it was unnoticable from above the engine, only when the car was on the lift could we spot it.
From a spare m20 - pristine sprocket with the woodruf key to go with it and the play was gone. Fire it up - same noise.

Listening at it again reveals the following:
From above: more pronounced between cyl 2 and 4
From beneath: more pronounced between cyl 5 and 6, but only if you listen without a screwdriver or similar to the pan. Screwdriver to pan says it's everywhere .....
Removing the alu cover in front of the trans and below the pan makes the sound more pronounced.
Flywheel doesn't have any play, but does have some slight oil drippings, that are spread by the centrifugal force starting from the flywheel bolts.

Now, what I am thinking - since those drippings are on the side, which faces the front of the car, is it possible, that the bolts have backed out and cause this rattle/clatter? I used brand new OEM units and torqued them down to spec, but you never know.
Otherwise the only thing that comes to mind is go back to the head and check every rocker arm, also warm up the engine and fire it up with the head cover off.

Any pointers are welcome.

[Lugnuts]

Haven't seen this explicitly mentioned in your previous posts - have you tried running the engine with the valve cover off to see if it's something in the valve train that's causing the rattle?

Edit: just noticed you suggested exactly this in your last post...apologies.

Is the rocker shaft locking key in the cylinder head installed correctly/flat?

but does have some slight oil drippings, that are spread by the centrifugal force starting from the flywheel bolts.

Sound like the flywheel bolts didn't have any thread sealant applied before install? They come from the factory with yellow sealant on them to prevent this from happening.

[gnmzl]

Hey Lugnuts,
I still haven't done the test starting the engine with the valve cover off due to lack of motivation to work on this issue anymore. But it is a must, since it DOES sound like valvetrain. For sure the next thing to do.

The rocker shaft lock key is firmly and correctly placed, checked it twice whilst previously looking at the valve lash.

The bolts did have the yellow sealant applied, it is the sole reason I went with brand new OEM bolts. But I wouldn't exclude user error (me not torquing exactly to spec or messing up something else)

For what it's worth, my rocker shafts are not OEM units, I forget the brand right now. And I have a small issue with them - at the front of the engine they are a tad too long and at the back of it a tad too short. This caused a huge oil leak the first 500 kms which I fixed. And yes, the locking key fits in place, all the holes line up, its just not correct lenght wise. I'll take a picture next time I get around this.

Thanks for the input, definitely made me think about the shafts being an issue.
Will update as soon as I chase this down.

[Lugnuts]

Funny you mention the rocker shafts not being a great fit. I bought a couple of Febi replacements years ago because, at the time, Genuine were listed as NLA. I don't know if that's still the case now. After installation I was concerned about how the rockers were lining up over the valves - almost as if the retaining clip cut-outs hadn't been machined exactly right. Some lined up ok, others seemed to be off a couple millimeters. It probably would have run fine and I was just being overly paranoid. I opted to swap them out for the Genuine shafts that had been in the head previously and were still in decent working order. I was happier with the overall alignment using the Genuines. Wouldn't surprise me to learn Febi is now making them too short/long.

One other thing I've seen overlooked in the past (not personally, just on a forum post) is forgetting to install the block/cylinder head alignment dowels. The head shifts slightly when the engine's running and you end up with oil in-feed issues. I'm guessing the lack of oil pressure/flow would be evident from inspection...