Big end damage diagnosis.

[Jezz_S13]

Hello, :)

The other day whilst in the engine bits shop I saw a chart like the champion one for diagnosing engine problems from spark plug condition.

Does anyone know where I could find such a chart showing big end damage and likely causes?

Thanks y'all :)

Jezz.

[Paul_S13]

Some haynes manuals have diagrams.

[Jezz_S13]

Oh right, I got a bunch of them, I'll pop and check them out.

I'll take a picture tomorrow for you lot to see and get your verdicts.

Cheers,
Jezz.

[Billy]

I've seen such a thing in an engine builders. It had bearings and pistons in various states of horror.
I think it was produced by AP, but I'm not at all sure about that.

Most bearing failure is oil related. The running clearance is critical, too little and the friction goes up taking the heat with it. Too much allows the parts to impact each other. Big ends suffer centrifugal starvation too, which increases exponentially with revs (you know where this is going, don't you?), and the only way to avoid it is to increase flow to the bearings. This means either crankshaft oilway mods and possibly main gallery mods (the best way) or more commonly, raising the oil pressure (wastes power, and can cause over oiling of cams etc).

Much cheaper to keep the revs down. (There, I've said it! :D )

I've just read your bit about the mains, which reminded me that big end starvation often leads to main bearing failure, since the mains supply the big ends via the crank webs.

[Jezz_S13]

Okay no more 8K :(:(:(

When Jez does my new chip I'll get him to put a sensible limit on it. Humph.

In my defense though I think it's because I've nearly ran out of oil twice (less than 2 Litres), one such occasion was TSC! I tried to put some in but it was so windy it just blew everywhere!!!!

What impact is dodgy mains going to have, if indeed they are dodgy?

Jezz.


Just read that again, not really much of a defense is it? LOL

[Jezz_S13]

Here is a piccie of the shells I took out, see if you can see anything wrong. :D:D:D

http://bagpuss.swan.ac.uk/200sx/bearings.jpg

[docwra]

The ones at the back are smaller than the ones at the front!!! ;) :D :D

[Billy]

Originally posted by docwra
The ones at the back are smaller than the ones at the front!!! ;) :D :D

Not only that, but three of them have worn away altogether! :rolleyes:

Is the one at the front missing a big chunk out of the middle, or is that just a trick of the light? Not that it would be a problem or anything!

Other than that, I've seen much worse. Much much much worse. Like steel shells hammered to the thickness of foil without a trace of copper left, or one shell turned until it covers 90% of the other, but at a 30 degree angle. (That engine was scrap, surprise surprise!)

I'd be surprised if the journals aren't OK with yours, Jezz. Oh, wait, you said that already! Doh!

[andyf]

Tee hee, I can't till May when I can post pictures from my bottom end ( OF THE CAR..)

In the meantime I have a picture of a broken piston here somewhere, it would be fun to see if anyone can tell me exactly how it seems to have broken.