Worn Cam Lobes and Rocker Pads???

[andyleonard]

1991 E30 M20 automatic 140K miles, adult driven, very well maintained, motor never opened, Castrol 20/50, cam lobes and rocker pads wiped.

 

What happened? 

[TobyB]

Quote

What happened? 

 

Castrol 20/50

 

Not approved for sliding friction.  

It's done that to me, too.

 

t

don't think with your dipstick.  Use ZDDP.

[AceAndrew]

To be fair, I've seen much worse on well-maintained engines.  But yeah, pretty clear indicator of no ZDDP.   

 

Also, when you say the motor was never opened, does that also mean no valve lash adjustments?  As the valve wears into the seat a bit, the lash gets tighter and can add greater pressure along those surfaces.

[andyleonard]

I was afraid you were going to say that....

[andyleonard]

7 minutes ago, AceAndrew said:

To be fair, I've seen much worse on well-maintained engines.  But yeah, pretty clear indicator of no ZDDP.   

 

Also, when you say the motor was never opened, does that also mean no valve lash adjustments?  As the valve wears into the seat a bit, the lash gets tighter and can add greater pressure along those surfaces.

No, no. 2 of the 3 owners have been BMW techs; all the maintenance and more. I meant the head's never been apart. It ran fine, no noise, valves adjusted.

 

I've seen this on a race motor with a cam and heavy springs or a stupid-high-miles motor or an oil's-never-been-changed-ever motor ... but never on a street automatic with hone marks still in the cylinders.

[Hans]

So what oil should we use? Not Castrol?

[AceAndrew]

Well, that valvoline vr1 20/50 w/high zinc would work.

 

 

https://adamsautosport.com/bmw-m10-m20-m30-engine-oil-guide/

[tech71]

51 minutes ago, Hans said:

So what oil should we use? Not Castrol?

This is $10 less than vr1 and quite suitable fora street car

Edited April 27, 2022 by tech71

[Schnellvintage]

Also be consistent with 3k mile oil / filter change intervals.   Use high quality filters. Not all filters are the same.

[Hans]

1 hour ago, tech71 said:

This is $10 less than vr1 and quite suitable fora street car

So high zinc? What about rebuilt M10s?

[Son of Marty]

All m10's need a high amount of Zink to lube the cam/rocker interface. 

[jimk]

Flat tappet cam followers need zinc, not just BMWs.

[Lorin]

Rotella 15w40 is another good not too pricy oil option. 

[TobyB]

I've pulled  apart a few BMW engines that looked like that.

 

Some looked like hell inside.

 

Others looked pretty good.

 

It really only takes one 'episode' to break down the 

hardened surface of the rocker and the polished

surface of the (soft) cam, and viola- it eats itself.

Once it starts, it doesn't stop.

 

Metallurgy.  It's part of rocket science.

Along with chemistry.

 

t

 

[andyleonard]

Science project time:

I've been told the pads on the rockers are hardened all the way through and guys  grind/reface them with no ill effect. I've also been told it's case hardening only and is maybe 15-20 thou deep, like a crank.

I'm assuming cams are all more-or-less soft, as they are ground and reground regularly. 

So, given that the stock cam and stock 1991 rockers gave it up with street use only, will there be more or less wear with a reground cam and resurfaced rockers? Or with a new billet cam and 2022 OEM or Febi rockers (are they not the same thing at this point?)