Roll Call: Spun Bearings

[sciamop]

I just picked up my second S13 (1991 Coupe/Automatic) with a hole in the bottom end: #4 rod went through the block on both sides! My 1993 Coupe had a hole in #1 and my 1990 Coupe has a faint knocking somewhere in the bottom end.

When I sold my BMW M330is race car, the guy who picked it up said that he once had a KA24E S13 that spun a bearing. A quick search on Zilvia.net for 'spun bearing' returns 4 pages of results.

The purpose of this post is to find out which bearing usually gives up the ghost and how common this problem really is... Let me start:

1991 Bright Red Coupe Automatic: #4
1993 Aztec Red Coupe Automatic: #1

[Jeff240sx]

#4 is common cylinder to lose rings and blow due to detonation/overheating. Spun bearing doesn't seem to be able to have a common candidate, because it's generally an over-rev or under-oil issue... and whichever it happens to it happens to.
-Jeff

[Andrew Bohan]

i spun my #3 on a dohc. low oil :(

[black s13]

i spun #3 on my dohc. dented oil pan = max of 25psi of oil.

[Andrew Bohan]

when i poured teh oil out of my pan, it looked like i had been using it to pan for gold in the creek. hella metal flakes and pieces in there :)

[sciamop]

#4 is common cylinder to lose rings and blow due to detonation/overheating.

Interesting... Why is #4 more prone to these problems than 1, 2 or 3?

Here's the result of the #4 disaster. It fell out when I was pulling the engine...

http://www.whistlehog.com/data/rod.jpg

[axiomatik]

I seem to recall that #4 gets less fuel than the other cylinders since it is at the end of the fuel rail, therefore running a littler leaner and thus more prone to detonation.

[fliprayzin240sx]

I threw #3 when my oil pump went out.

[Andrew Bohan]

so low oil kills #3 and low fuel kills #4?

[ledzeppelin240]

The real reason for cylinder #4 being more prone to detonation is due to the EGR valve that is where it is located closest to and if it fails that cylinder runs a little, or a lot hotter.

The injectors all get the same amount of fuel and if a cylinder was running leaner it would be producing more power and be a little hotter. Which would cause a rough idle, and the idea of it is that each cylinder producing the same amount of power, hence a cylinder power balance test. No more than 5% diff. Between cylinders.

I would say lack of oil due to over revving…

[fliprayzin240sx]

Well as far as leaning out...its tru that when you lean out, the cylinder thats closes to the FPR has a tendency to blow cuz that would be the one the get the least amount of fuel. So depending on whether your running a KA or a SR, will change on which cylinder it would be. KA fprs are in the rear so #4 will lean out more, while SRs are up front so #1 will lean out first.

[ryan hagen]

but if fuel isnt getting to the fpr you have no pressure, the fuel rail has to be full for any of them to work. its the furthest from the throttle body? and air flow i though had something to do with it the air has a longer run at it? the number 4 fuel thing also might be true if you have low pressure but you must have some pressure. a spun bearing is almost allways from oil or lack of oil, number 4 is the furthest from the pump so if you have low pressure in the oil system the resistance is the beaing tolerances, if they are sloppy you have low pressure and the pressure drop by 4 in a low pressure situation destorys four, the cylinder head can also have problems when low oil cause its the highest point. the oil pressure is regulated at the pump so it works differnt than fuel pressure which is regulated before the return line.

i lost rod 3 in a no pressure oil situation. my oil pressure gauge adapter broke off, (never use brass t's) rod 4 had steched bolts but didnt blow. 1 & 2 were fine with badly trashed bearings.