21 replies to this topic

[MiniLuke]

Removed 998 engine today to do one or two bits and pieces and thought I would check the main bearings.


Any thoughts on the causes of the scoring.... they are only on the flywheel end. Could it have been crap in the oil?

[Guess-Works.com]

Yup, or swarf left in the oil galleries from a recently machined block or crank..

and need replacing, also check the crank.

[Cooperman]

Remove the oil gallery plugs and thoroughly wash through with paraffin, followed by a good water-soluble de-greaser and flush with a pressure hose.Thenwash with brake & clutch cleaner and blow through with compressed air, then spray into the galleries with WD40 to prevent any rust developing until you re-assemble.

[charie t]

Yup, or swarf left in the oil galleries from a recently machined block or crank..

and need replacing, also check the crank.

Not from a crunchy gearbox?

[Guess-Works.com]

It's fairly difficult for swarf to get through from the sump to the main bearing galleries...

First it has to get past the magnetic sump plug, the gauze on the oil pick-up, the oil pump, and finally the filter before it even gets into the galleries.

[MRA]

We always use brushes to clean our engine components, as anything else doesn't really get it clean, as witnessed by a recent customer who watched me clean his "clean" block with my set of brushes, his surprise at the amount of dirt that came out with the brushing.......

According to AE reports 46% of failed engines, fail due to dirt, ie not being cleaned correctly in the first place, also the comments were that it is normal that a combination of faults cause a failure, dirt and poor fitting, checking etc.

And that if an engine bearing has failed, fitting new bearings is a common mistake..... the engine will need to be fully stripped to find the cause and then rectify this issue, this has always been our philosophy, it's just nice to get the reasurance from a major manufacturer that spends millions on research.

[MiniLuke]

Yes, I am crap at building engines.....

The Big end bearing is the same at the flywheel end..... oh well...

[MRA]

Yes, I am crap at building engines.....

The Big end bearing is the same at the flywheel end..... oh well...

If it was done by a company I would agree with the "c***" bit, however you gave it a go, now all you have to do is look at the areas of failure and make sure you find out how to rectify them so you don't repeat the situation.....

Or alternatively spend the hard earned cash on a company that has already got a good reputation for engine building...... your choice really.

[Dan]

It's hard to get the oil gallery properly clean at that end becaus of the oil PRV seat, but you must persevere. As Martin says there is always more dirt than you might think. Pipe cleaners and bottle brushes.

[Cooperman]

I have a very long round brush which goes right along the main oil galleries. I first wash the complete block with a water-soluble de-greasing agent and flush with high-pressure water. Then I use loads of paraffin and brushes, then blow through with comp. air, then drag small pieces of cotton rag through the galleries which I've soaked in paraffin. Then, when they are coming out absolutely clean I flush the entire block with 'Brake & Clutch Cleaner', then blow with comp. air again.
Then you could eat your dinner off the inside of the block.
Then and only then can the re-building start.
After each further machining operation, such as block decking after the first trial build, the entire cleaning process must be repeated.

[bmcecosse]

The big-ends are fed with the same oil that goes to the main bearing - so not surprising it's also scored really.

Edited by bmcecosse, 30 May 2011 - 07:09 PM.

[MiniLuke]

Right, Bank Hol Monday spent taking the thing apart, completely. Picnic anyone?


What's the deal with the journals then??



Also, any opinion on the laygear?


And this....
http://i965.photobuc...od/DSC_0291.jpg

[mini13]

the gears look ok,

for the crank drag your fingernail across and feel for ridges, Although it looks to me as though it might be alright, give the journels a light polish with some 1200 wet and dry and some WD40 (an a strip)

Also get a brush down the crank drillings

[MiniLuke]

Well, the big end journal on the forth is knackered.....

Crank at MED right now for a regrind.......

[MiniLuke]

We always use brushes to clean our engine components, as anything else doesn't really get it clean, as witnessed by a recent customer who watched me clean his "clean" block with my set of brushes, his surprise at the amount of dirt that came out with the brushing.......

Brushes bought.... wish I had done this first time round as they are very cheap to buy, compared to a crank regrind!!