Thrust Bearing Failure

[JETGSR]

yet another case of the dredded Thrust Bearing failure!:thumbsdown:

this case shows a definate case of oil starvation to the thrust washer,
and before anyone comments - oil pressure to the crank is in excess of 80psi and all gernals are clean and flowing!:thumbsup:

so why did it fail so ugly? My guess would be a combination of heavy clutch, inturn incerficient flow of oil to the thrust washer.:thumbsdown:
There is talk of mis alignment of endcaps all over the web too, This block was machined (tunneled) with full gurdle and torque plate on, including thrust face on block. and yet it still wore the thrust bearing!:thumbsdown:

I have included a couple of pics of mods to the oil supply to the thrust washer face,
at this stage the crank is shot and there is far too much play laterially - so in other words it is stuffed but i'm looking at what the wear will be like for the new motor.

STUFFED INFO

clearence of worn bearing 1.55mm <-- well and truly stuffed!
bearing wall thickness new - 2.04mm
bearing wall thickness old - 1.23mm <-- bad
(note - crank was worn too)

clearence after new bearing fitted .027 tho - bit over half a mil
like i said truly stuffed concidering preloaded clearence should be something like .003 tho

So the gist of things is - I still have a 300kw 7 bolt engine with a **** load too much endplay! BUT a lot less now!:huh:

Ok what did I do to try and prevent further wear to the new bearing

cut a new oil gallery from the main bearing feed to the thrust washer face, also modifing the thrust bearing to allow the feed of oil through to the face.

loaded gurdle and crank to bearings before torquing it all down (normal practice)

In my case there was a definate oil starvation issue, so we will see what it all looks like down the track.

Some might remember I had dramas with some cams wearing out and filling the motor with ****! those bearings apart from all metal in them, had no signs of wear!

I think there would be 10000ks on this motor, or something like that!
So in terms of age - very young!

Maybe I'll drop a stroked 6 bolt in there.:thumbsup:

 

[rob323]

It's all that "cruising" you do in it Troy.
Time to dry sump it and run a separate pressure feed to the crank.:w00t:

 

[bazeng]

Damn that sucks!

What did you rev the motor to?

 

[JETGSR]

7500rpm rev cut redline(shift light) 7000rpm

have worked out a few flaws in the mitsu system so going to drive it till it breaks

then fit a new stroker crank do the necessory mods to sort out the issues.

find it very hard to believe that there is no way to fix it! Mine is an oil issue not alignment issue, so I have somewhere to start!



Rob - how does a dry sump work on a 4g63? do you have to modify the oil system much?

JetGSR

 

[rob323]

Works the same as on any other motor.
Small sump, scavenge pump sucks it from the sump into the reservoir.
Mechanical or electrical pump sucks it from the reservoir and pumps it into the engine.
An electrical pump will supply full pressure during start up as it's not waiting for the revs to rise.

Or maybe look into the canisters that they have on trucks which prime the oil system before start up.

 

[JETGSR]

how am I going to feed crank first? isn't that what happens now?

Pump - filter - crank - squirters - top end of motor - turbo then it all dribbles to the bottom and starts again?

 

[rob323]

But how much oil pressure do you get while just cranking it?
Do you know if it was oil starvation at start up that caused it, or oil starvation while running?

 

[DOUGMO]

maybe an accumulator system, like a moroso one.

 

[EVO-00X]

Would be interesting to see if the groove you've cut helps reduce thrust bearing wear. It'll be worth knowing the difference it makes later on when you tear the motor down again (whilst using the same clutch).

I have no doubt whatsoever that a high clamping force heavy duty clutch is the major cause of this type of problem. Im more inclined to think that the added force on that particular bearing when using a h/duty clutch increases the amount of heat that bearing endures. As its already lacking a decent oil supply it only exacerbates the problem for both the side journal of the crank and the thrust bearing.

Sadly, the excess lateral movement the 7 bolt crank gets as a result (crankwalk) is way too common when h/duty clutches are involved that it cant be dismissed as the major cause. I know from reading US websites that when guys get a hold of good automatic transmission Eclipse engines and rebuild them (most non Hyper RVR turbo motors basically) and then put them into an Eclipse running a manual transmission and h/duty clutch, they end up having thrust journal and bearing issues. Without getting into a big crankwalk debate I'd like to state that to this date I have never heard of an automatic transmission 4G63T suffer this problem on any variant of an RVR, Eclipse, Galant, late model auto EVO's etc. The 6-bolt crank bottom end also doesnt suffer from it.

Have you got a pic of the corresponding side journal on the crank? It should be worn and stepped in a fair bit now, sort of looking like a very worn brake disc rotor.

 

[JETGSR]

that is exactly what it looks like! and yes it has worn .025 thou so the crank is stuffed!

but we have an option of building up a new bearing with brass, machining the crank back to flush then machine the bearing to fit crank! (there is a lot of technical bits in the middle there but I'm not going into that now)

One theory put to me tonight was when my input shaft broke - i rolled it (idled) for about 1/2 a k down the pacific hwy - yes it rolled really well! from BP at Beenleigh to over the logan river bridge to about 20mtrs from the eagleby exit! (lucky)

O yeah back to the theory ... if the clutch loaded to the flywheel - being a heavy clutch no oil would make it to the thrust therefore wearing it very fast?

not sure how sound it is but they had seen simular results in big V8 stuff?
the short of the long is any way I look at it , I need a new crank!

I do believe that oil being pumped to the thrust washer will fix the problem
as if you lube 2 frictioned surfaces and maintain the lubrication. Wear is reduced 100 fold
and so is heat, even if the surfaces are not perfect minor wear will only result!

So YES heavy clutch is a MAJOR contributor to the problem, and so is Oil supply to the thrust washer. Unfortunatly we will always need a heavier clutch to get the mech traction. (Ok twin plate clutches are a step in the right direction)

Another option is making a feed from the now missing balance shafts to the thrust washer (like the oil squirters for the bore)

Has anyone got a 7 bolt 4g63 apart that I can have a look at? IN BRISBANE! south side pref.

please let me know as I might do a bit of poking around in there for a look see!

and Craig I might want a look in your 6 bolt too!

JetGSR

 

[EVO-00X]

Just be careful from where you want to pump oil from as you dont want to be robbing oil from anything before the galleries. Its a shame there wasnt a dedicated squirter for the main thrust journal, I can hear your mind ticking already lol.