Old engine evaluation (M180.924 - ponton)

[rbtoj]

So, new followers then...

Yes the affected pistons are the ones sticking higher, only by a little though.
Just to make it clear, this is my first time disassembling an engine and I don't have an engine stand, so progress is slow!
But don't worry, as soon as I get into the bottom part, I post my findings. I too am curious about the piston/valve thing.
And thanks for the good luck, I'll need it!

As for the ethanol, it is only a problem for plastics and rubber components not design to chemically withstand it.

[Stretch]

Originally Posted by rbtoj

...
As for the ethanol, it is only a problem for plastics and rubber components not design to chemically withstand it.

Not exactly - it depends


The best explanation I've found so far (which doesn't involve internet shouting) is here


https://extension.psu.edu/fuel-ethanol-hero-or-villain


It is a question of "know what you eat" and adjust accordingly if possible.

[Stretch]

Points to consider:

1) If say a camshaft breaks at idle it is possible that only a few (or singular) pistons and valves touch - I guess however if you've got different sized bores and pistons then the worst two were removed and the engine was cobbled back together (just a guess!)

2) The height at which the pistons protrude from the top of the engine block is usually a prescribed limit in the FSM - if you have a mismatched set of bores and pistons then the chances of getting a smooth running engine reduce - an apparently small discrepancy in volume can make trouble. It is much better if all of the volumes are the same - that's what decent engine builders / modifiers / designers strive to achieve.

3) If you can see wear in hardened surfaces you can expect accelerated wear from now on - using particular oil properties or additives isn't going to fix what has gone

4) Visible - "Whoops I dropped it" damage is generally a bad sign (!)

[jsp300D]

Cant give a like on Stretch but, thats what I was thinking.

[rbtoj]

I've made little progress the past couple of days. Basically I've got the sump out but soon ran into excessively torqued bolts. The main bearing bolts came off ok (revealing bearings worn evenly to the copper and a seemingly serviceable crankshaft), but the connecting rod nuts are stupid tight for their size. They are only 14mm and the shape of the rod cap is such that you can't get full contact on the nut. As a result, I've already broken one socket and stripped two of the little buggers.
So I'm gonna have to grind a new socket to fit, but my dremel lost the battle against those 20 odd bolts on the water jackets.
In conclusion then: fix dremel > grind socket > deal with Hulk's nuts...

[Sugar Bear]

Is that a tack weld on the rod nut?

[rbtoj]

Nope, just a strange oil drop.

[rbtoj]

Quick question: Does anyone know what is the correct torque value for the connecting rod bolts? I have the Service Manual for the 220s, but the only torque value I saw anywhere was for the head bolts. Strange...

EDIT: Never mind. Just found it.

[Tomguy]

Are you using a 6 point 14mm? If so, try another socket, ex if you're using a 1/2" drive try 3/8", if 3/8" try 1/4". I have 6 point 14mm in all 3 of those, you should too - and it appears you need it. The right tool for the job is a must when working on engine internals!

[97 SL320]

Originally Posted by rbtoj

I've made little progress the past couple of days.

The top right of pic 1. It looks like bearing material is being hammered out.

In any event, the crank will need to be sent to a machine shop to be cleaned, magnafluxed and measured if you are going to reuse it.

Also, the connecting rods will need to have the big ends measured for roundness. Insert type bearings rely on round bores of the proper diameter to function properly.