[qwerty123]

hi guys,

standard g13ba with 204,000km has recently been making this noise,

very loud when cold at idle and under load.

once hot it is barely audible and seems fine,

only started once i changed the oil (New 10w40) no idea what the previous owner had in it. And now i just tried 20w50 and it makes no difference.

Ive adjusted the valve clearance to spec and it seems to go away a bit when i pull an ignition lead. but still audible.

it seems to be getting worse. my gut tells me rod knock but it goes away when hot. very confused.

no knock when rolling in gear

[jdk81]

Id guess a spun bearing
Did you fill the oil filter prior to installing, when doing the oil change?
Running dry for a bit can be enough to cause it, especially on an old engine

It may be something simple, but not fixing a spun bearing asap may ruin the whole motor

[qwerty123]

i suppose what your saying is possible. but it didn't happen straight away it took about 100km of driving to show up.

also dead cold if i pull #3 lead noise disappears

[jdk81]

So id consider its the bearing on conrod 3.

[qwerty123]

Rod bearing or main crank bearing?

From what i have heard rod knock should get worse/louder when hot as the oil thins out. I'm sure the main bearings follow these same rules.

This is the part that is confusing me and makes no sense.

thanks for your input

[jdk81]

Check my build thread.
The block with the holes in it went bang.

Was a light knock and didnt sound like a typical bearing issue.
Didn't change when it got hot etc.

Another block had a funny sound as well (not typical), and its bearings were kinda rooted too. It wasnt far from exploding too.

Rod and crank bearings werent expensive

[qwerty123]

Update.

pulled the pan to have a look. everything seems fine,
I tried to move the conrod up and down and could not get any sound,
only when i moved them side to side

here is some pics they are worn but is it enough to knock??

bottom


top


crank

[jonno_racing]

Gudgeon pin knock then?

[qwerty123]

definitely not wrist pins, they are solid,

along with everything else the bottom end looks mint, pistons and bores are perfect (can still see hatching)
top of the pistons are absolutely carbon free. (borescope through spark plug hole)

no sludge nothing in sump
ive ordered new rod bearings and will see if it makes a difference
I'm starting to wonder if it is head related as i always thought it was coming from #3 exhaust port area, no leaks though

also starting to wonder if its been rebuilt previously. are the sumps sealed with RTV or cork from factory

[qwerty123]

Just fitted new rod bearings,

No difference.

It has to be piston slap or valve related.