Rebuild step 1

[P30inbuffalo]

Here's a picture of the corrosion, sorry cant figure out how to resize this. Hitting "control-minus" will shrink your screen view.

[lat 64]

I think that comes from lots of low-speed running.
There was some discussion about it somewhere on the forum.
I'll dig around.

you have a pronounced case for sure.

[lat 64]

First Google hit was a winner:

http://www.substech.com/dokuwiki/doku.php?id=engine_bearing_failure

Some great pics here. Now I just have to read it

russ

[hanleyclifford]

Russ - Good research. Under the classification "bent connecting rod" which shows wear at the edges of the shells, question - could this phenomenon also be caused by excessive crankshaft end play? Hanley

[P30inbuffalo]

More specific information

I'm still getting my terminology right so please bear with me. The crankshaft main journals are smooth. The main bearings are what's pitted.
On the flywheel end, the outside area only of the lower bearing and the inside area only of the upper cap bearing are pitted. On the transmission end, the block main bearing is fine, and the main cap bearing is pitted on the inside only. As if there were unusual up pressure on the flywheel end of the crankshaft or down pressure on the other end-?

This engine would not go to high rpms in forward, regardless of the throttle setting.

On another issue, would it be wise to replace the rod journal bearings regardless of how they measure, to err on the side of caution, or is this a waste of money?

[P30inbuffalo]

Hoisting the engine- pics

Several people have asked for more pictures from hoisting the engine, here's a link:

https://picasaweb.google.com/hamburgjl/Atomic4Rebuild?authkey=Gv1sRgCPyfhc2A09HTOA&feat=directlink

[thatch]

"A4 acid stomach?"

Jim,
The pitted bearing shells appear to be a classic case of acid erosion. Acid forms in the oil over time with the presence of water. Although there are acid inhibitors in the oils we use, they deteriorate over time, particularly in the pressence of excessive moisture. One of the main reasons for this, in auxialiary sailboat engines is that they (in many cases) tend just to be used to get us in and out of our slips and are never thoroughly warmed up, creating condensation. The solutions to this problem are generally considered to be, more thorough engine warmups and, at least, yearly oil changes done before the winter layup. The wear pattern on the bearing pictured looks very normal, except for the erroded areas, but should certainly be replaced.
Tom

[lat 64]

Russ - Good research. Under the classification "bent connecting rod" which shows wear at the edges of the shells, question - could this phenomenon also be caused by excessive crankshaft end play? Hanley

My first thought is no. There is enough "float" on the wrist pins to allow for a worn thrust bearing. The rods would just move a little for'd or back. I think if you had enough endplay(worn thrust) to make the the rods interfere with things, you'd have some very big chunks of glitter in your oil.

Bent rods are common. Reconditioning rods is a typical machine shop job. I have only done it a few times under the watchful eyes of a pro.
There is a jig that you put the rod in and then measure it's bentness. Then you twist it with a big bar to make it right again. This is followed by resizing the big end and honing the both ends to make it spec again. New bushings for the small end may be necessary. Don't do this at home kids, just something more to consider.

I digress again,
Russ

[67c&ccorv]

I'm still getting my terminology right so please bear with me. The crankshaft main journals are smooth. The main bearings are what's pitted.
On the flywheel end, the outside area only of the lower bearing and the inside area only of the upper cap bearing are pitted. On the transmission end, the block main bearing is fine, and the main cap bearing is pitted on the inside only. As if there were unusual up pressure on the flywheel end of the crankshaft or down pressure on the other end-?

This engine would not go to high rpms in forward, regardless of the throttle setting.

On another issue, would it be wise to replace the rod journal bearings regardless of how they measure, to err on the side of caution, or is this a waste of money?

Well, the good news is the wear occurred on the easily replacable main bearings and not on the crankshaft main bearing journals (you hope?).

You will have to mike the crankshaft main bearing journals to determine whether they are worn and/or ovalled...

...your Mk I eyeball will not be able to discern this.

Once that is determined at the minimum if it is just a main bearing replacement issue the crank journals will have to be conditioned before the whole thing goes back together.

BTW...everyone knows it is a no-no to touch a new main bearing with your bare hands, right? Maybe that is how that acid etching started in the first place???

[hanleyclifford]

Go back to post #18 of this thread and study the link. You will see the very picture of what happened to your bearings and the reasons for it. I think a new or reworked prop is in your future. And yes, by all means replace the rod bearings along with the mains. Make sure you don't have undersized - should be stamped on the back of the shells.

[thatch]

If this was a case of wear, why are there no signs of rotational rubbing?. Jim's pictures are of the front and rear main caps and their bearings which means that the crankshaft (which is a very stout piece) would have to bend considerably to cause this type of wear pattern. It is always good practice to measure everything in the rotating assembly during a rebuild, but don't ignore the fact that this is a newly acquired (at least 30 year old) A4 that may have had little or no maintainance for quite some time making it a prime candidate for acid deterioration.
Tom

[lat 64]

This engine would not go to high rpms in forward, regardless of the throttle setting.

I'm thinkin' this is big clue. Some prop or load issue?

Those "worm holes" are strange things. They do look like some stainless steel crevice corrosion I've seen, but I'm leanin toward the low-speed issue.

This is all academic, since this engine will be well maintained from now on and the shaft will properly aligned when it goes back in anyway. Right?

Got a color picked out?

Ruz

update:
Wow! I just found an even better site.

http://www.agkits.com/bearing-failure-analysis.aspx

Some more extensive descriptions here.
Just a thought here; My brother-in-law has done much research on metal fatigue in acid environments. He says it will contribute to crack growth during stress cycles. Probably something from all quadrants beating up this poor bearing.

R.

[thatch]

Lat64,
Agreed, once p30 completes his rebuild and the correct prop is chosen and with proper engine care, I'm confident that the problem will go away. Now, if we can just can coax him into going to a FWC system, he will probably wind up with an A4 that will outlive most of us.
Tom

[ndutton]

P30 Jim,

Apologies if I missed this but exactly what size prop were you running?

[P30inbuffalo]

P30 Jim,

Apologies if I missed this but exactly what size prop were you running?

Dont know the prop size but I will check this week. Color, I'm thinkin original bronze but now I'm thinking about it.