Camshaft/Rocker wear. Head oiling?

[zaq123]

Ok so I go this low mileage (after the rebuild) 885 head. Disassembly shows that Intake rockers and cam lobes are more worn than Exhaust side. Pretty much all consistently have more wear than EX side with 1 and 6 IN lobes being not too bad. 2-5 lobes look terrible.
IN and EX lobes are next to each other on the cam so it's not like spray bar can oil EX but not IN. I checked lash before disassembly and it looked good across all valves. I also noticed the worst worn rockers have eccentrics that are sort of more worn as well.
What can cause this issue? Oiling port is on EX side. Does the oil fills IN rocker arm shaft and oil that side after cam bearings get full and excess oil gets pushed into IN side via holes in bearings?
Could be that this head has worn camshaft bearings which creates oil pressure loss to IN side (cam bearing clearance too large due to the wear)? Wondering if this head is not a good candidate for another rebuild.

Your thoughts..

[82eye]

so this was a fresh built head that went south? if so that's an ultra agra ouch.
curious to know how deep the build was on the head.

i don't have a lot of suggestions. i refreshed my head and went with a regrind cam and hd rockers - not getting into the hd rocker debate thing here - valves were re-used with a simple grind. 2 things that stand out to me is we were told - don't tip the valves if reusing, and re-use the valve springs unless really shot.

the other suggestion we got was literally new everything. sorta one or the other. our goals were modest so we went cheap.

nothing in that is a huge change to the head so i can't see that effecting oiling. i farmed out the machine work and completed the head myself. they are super simple. anything weird would get noticed on assembly.

edit: eccentrics / hardware was all new

[zaq123]

so this was a fresh built head that went south? if so that's an ultra agra ouch.
curious to know how deep the build was on the head.

i don't have a lot of suggestions. i refreshed my head and went with a regrind cam and hd rockers - not getting into the hd rocker debate thing here - valves were re-used with a simple grind. 2 things that stand out to me is we were told - don't tip the valves if reusing, and re-use the valve springs unless really shot.

the other suggestion we got was literally new everything. sorta one or the other. our goals were modest so we went cheap.

nothing in that is a huge change to the head so i can't see that effecting oiling. i farmed out the machine work and completed the head myself. they are super simple. anything weird would get noticed on assembly.

edit: eccentrics / hardware was all new

Well my freshly rebuilt head was cracked (was never tested by machine shop). So I found another head that I want to use (it checked out for cracks) but I'm concerned about cam bearing wear on it. The head came from recently rebuilt engine. I just want to understand what can cause IN rockers/ cam lobes have more wear that EX side.. Are worn camshaft bearings to blame there?

[82eye]

Are worn camshaft bearings to blame there?

there are no cam bearings in an m20

edit: the head can probably be line bored and then bearings installed for a repair though. i've never done it or had it done.

[digger]

What do the housing journals look like and feel like ? You are unlikely to find one that is mint but you dont want it shagged

[zaq123]

What do the housing journals look like and feel like ? You are unlikely to find one that is mint but you dont want it shagged

they look scored. I just trying to understand how camshaft lobes/rockers can be badly worn on IN and not EX.. They are right next to each other.

[zaq123]

there are no cam bearings in an m20

edit: the head can probably be line bored and then bearings installed for a repair though. i've never done it or had it done.

I meant bearings/journals where cam journals ride, the part of the head.

[nando]

they look scored. I just trying to understand how camshaft lobes/rockers can be badly worn on IN and not EX.. They are right next to each other.

there's an oil spray bar on the M20 head. maybe it's bent? (pointed away from the intake side), or clogged and not spraying evenly. But basically all lubrication on the rockers happens from that spray bar and splashing. there are oil galleys for the cam "bearings" (which aren't really bearings, it's just the cam journals inside the aluminum head casting).

Oh there is also oil through the rocker shafts, but I think that mainly is for the rocker arm bronze bushing, I don't think that gets to the rocker pads.

[zaq123]

there's an oil spray bar on the M20 head. maybe it's bent? (pointed away from the intake side), or clogged and not spraying evenly. But basically all lubrication on the rockers happens from that spray bar and splashing. there are oil galleys for the cam "bearings" (which aren't really bearings, it's just the cam journals inside the aluminum head casting).

Oh there is also oil through the rocker shafts, but I think that mainly is for the rocker arm bronze bushing, I don't think that gets to the rocker pads.

bar is clear and not bent. Also imagine M20 camshaft for a second: IN and EX cam lobes are right next to each other. I know the oil bar just supplies like an oil stream and not like pressure spray or anything .....but still, i just don't see the bar oiling only EX lobes on the cam. And it's consistent: IN cam lobes/rockers (except 1 and 6) are chewed up when EX is perfectly good. Something I have a hard time understanding.

[TobyB]

If you're sure it's not oiling,

are the intake springs stiffer than the exhaust springs?
The intake valves are heavier, and in a high-rev situation,
need more spring to stay in contact with the cam.

Along with this, was the engine run over 6k rpm? Extra wear
on the valve train can indicate a little valve float. I always seem
to just break the rockers when I float valves, but I'm... well, me.

And at the other end of the spectrum, are the springs too weak?
This would let them float (intake first, for both weight and suction)
at a lower rpm, with less chance of rocker destruction. But extra
wear on the contact parts...

jus' thinking with my keyboard,
t

[digger]

As long as the casting in question has all the oil holes and they are clean, and is in good enough condition i wouldn't overthink it