worn out engine bearings after less than 500 km.

[j-f]

Hi all,

I got a bearings failure on my engine shortly after I rebuild it. I'm dissasembling it and bearings seems to loose their coating.
everything else just look brand new.
The engine case had been check by Udo, cranckshaft had been balanced and checked less than 10.000km ago.
I did a rebuild to change camshaft combo, add CR etc... oil pressure was good at 5 bars at idle when cold and about 1 bar per 1000rpm which seems to be good.
combo is .
Stock balanced cranck
Unitech rods
87mm cylinders
SLR XF 284 camshaft, Bugpack 1.4 rockers,manton thinwall pushrods and dual springs.
040 home ported heads with 9.0cr
Shadeck hd oil pump with full Flow, Mann w940/1 oil filter.
Globaly, it worked as I expected but quickly lost oil pressure.

I used Total quartz racing 10w50 oil which is API SN/CF rated, with a bottle of zddp max. Can it be a oil compatibilty problem? Zddp additive incompatibilty, bad bearings? Bad assembly? I try to understand before rebuild...

[MC Dyno Don]

It would be most helpful if you can show some pictures that show your concern.  We will wait to see your carnage sometime soon. Hang in there....

[Martin S.]

I don't understand the problem 'quickly lost oil pressure'. Do you get 10 psi per 1000rpm oil pressure? Does the pressure go down when it heats up?
I can't see the coating on the bearings being important. When my engine was built Steve hand rubbed with bearings with paper towel and WD40 to add clearance so that oil would flow properly thru the bearings because too tight is not correct. Bug engines can have problems with the oil pressure relief bore leaking pressure so make sure yours isn't wonky.

[j-f]

Sorry, I typed my first post with my smartphone, I made it short.

During the first 300km, the engine worked fine, oil pressure was good and everybody was happy. Then, I over revved it due to a loose fuel hose that get stuck in a carb shaft will I was changing gear... It revved well beyond 6.000rpm. My tach goes to 6000 and the needle get stuck 1cm past the limit. I took me 3-4 sec to shut it off. Belt broke and fly off, and I even wasn't doing something dumb as I was going to the bakery...
I don't know if this can be a cause to the problem? Engine ran fine after that, but oil pressure is dropping since. I now only had 3bar at start up and when engine is barely reaching 80°c, I only had 0.5 bar of pressure at idle and about 2.5 @ 3000rpm...
I first check if the oil pressure relief valves where not stuck and they where fine (but I didn't check their bores, I will do that), I also check the condition of the oil pump which looked fine (I dont know how to check clearance between gears though ). I also changed the oil pressure sender. (VDO 5 bars)
I tore down the engine today. I found scored bearings that flacked off for both the cranck and the camshaft, rods bearings where a little better but already showed signs of wear, everything else look fine. No scored cranck journals, no pitted cam followers all look fresh. I think I saved the engine by not driving it anymore when I suspected a problem.
I will check the cranck to see if still within specs, I don't think the case can be damaged or can it be?

I asked advices from 2 mechanics friends who are into vintage cars and VW and they both think to a lack of oil that scored the bearings.

Crancks bearings are Silverline and cam bearings are Mahle dual trust. cam followers are CB lightweight and they look OK.

[Martin S.]

2.5 bar at 3,000 rpm (or 15x2.5=37psi) is enough oil pressure, and .5 bar or 7psi at idle is ok when it's hot so you could have enough oil pressure. What is questionable is was there enough oil flowing thru the bearings? If the clearance is too tight, no oil gets thru and the bearing starves for oil and overheats, especially when new. Racing engines can't wait and run slowly til bearings wear in, so clearances are correct at start up.

[Jim Ratto]

if it was oil starvation, you would see rod bearings going away. And what about flywheel thrust surface and shims? Any signs of trouble there?
do you know what journal to bearing clearances were at # 2 main bearing?
Did you mention your oil temperature? Sorry if I missed that.
A short rev above 6000 on a good motor shouldn't create damage.

[j-f]

Engine never gets hotter than 80°c. So if the bearings where too tight the engine would have overheat or at least will have reach a higher oil temp? I use the stock thermostat and cooling tins. No external cooler.
As the cranck is a used stock VW one, I don't check the clearances. I did check the cranck journal which where within specs, but can not remember them. I thought with used parts, clearances would already been on the loose side. > Something I will not assume next time...

[alex d]

was the oil cold when you had the overreving? maybe oil was too thick to get where it should in time

[j-f]

was the oil cold when you had the overreving? maybe oil was too thick to get where it should in time

That's possible. It happened During a winter drive less than 10km from home.

I took pics of the endplay washers. The midle one is blakcish.

[Martin S.]

I haven't tried revving a stock crank to 'well over 6000 rpm' but from what I've heard they don't do well above stock rpm (4 - 5000 rpm). Maybe that's what happens? Try and find a counter-weighted crank as they are reco'd for any engine that revs above stock rpms.

[j-f]

I'm back with a question.

I have a used CW 69mm cranck to replace my stock one. It's a welded one and it's in second size on mains and rods journals. I checked it and all are within specs and clean ,but #4 (pulley side) shows some irregularities like waves. I check and their is 0.01mm to 0.02mm variations between them but still within specs, between 39.49mm and 39.47mm. I checked my old cranck and it's the same kind of wear Is this some wear you already saw or I better go and buy a new one? This engine still got good oil pressure before dismantling.

It's a bit hard to explain I know. I try to draw something to explain...

[busbusbus]

wear in center cam bearing looks to be caused by ovalled out hole (maybe needs resizing or lineboring)
damage in main bearing can be caused by old oil . i have seen some of them with similar damage on engines left with contaminated oil for long time. was the engine left in a humid place for long time before first starting? just a tought

irregolarities in the #4 main looks to be typical wear caused by the shape of the 4 bearing. the crank has little wear only where effectively touches the bearing (startup).