What do these bearings tell you?
 

Anything?

dirt,iol thin and crank/rods clearances need to be adjusted and trued.

What about the diagonal/ crosshatch type marks?

scrotch biting out the poor fit.

Someone removed bearings rubbed on them with scotch brite and reassembled.:popcorn:

x 3.

While we're at it.

I think sutphen 30 wins the prize. I didn't want to prejudice the response but the mains in the block were about 5 thou too big (but then why were they scotchbrited?) and hadn't been aligned. We were also guessing the scotchbrite clearance job and I recently switched to a lighter weight oil. Shouldn't have been any dirt though unless it got there during assembly or debris from the damage or possibly a used oil thermostat housing that was put on.

I have heard of people sanding a little off the back of a bearing to gain a few ten-thousandths in clearance, but to my limited knowledge it is a big no-no to sand the face of them.

If the mains in block were 0.005" to big scotch brite would make it worse.

I'm sure this had something to do with the looks of the bearings.

Right. Don't know for sure why stuff was done

Bores were out of round and tapered. Although I did get them hot

Do you know what the bearing clearances were? .0035? Bigger?

And there were .180 of small block shims under the springs.

I was referring to the detonation on the Pistons. It will hammer the hell out of the bearings.

What do you see in the way they look? Are you referring to the dirt that sutphen mentioned? Trying to at least learn a little from the experience * edit just saw your reply. No one else mentioned detonation. What are you referring to.

Comp was 9.0 , 36 ° timing, 93 octane

Post #7. 1st photo.

The top of the piston in the one pic looks like it was sand blasted. That from detonation. The pic to the right of that one looks like it has a small chip missing around the outside (exhaust side) that's detonation. If you have the Pistons out and flip them upside down I bet they have burnt/ baked oil on the backside this is due to detonation. You probably also have black stripes on the sides of the Pistons this is from detonation. That's why it is often referred to as Black Death. Do not re-use those Pistons. At a minimum you need to carefully measure the ring gaps in them. What happens when they detonate is it shakes the hell out of the rings and the ring land gets oblonged in the back of the groove. Also when they start shaking you loose seal and end up with the black stripes on the sides of the Pistons. Detonation will eat the bearings right out of a motor. Make sure you have the main line checked carefully as well as the deck of the block (front to back side to side). It can and will move things all over the place.

I was looking at the scoring in the bores. I thought bearings looked good except for the uneven wear and scotch brite marks. Might have been the flash making pistons look like that. Afr got into the 13s when cruising. Was in the 11 and 12s at all other times including wide open iirc

Oh yeah you detonated the piss out of that thing. Throw the valves away also.

One more thing you will see is the second ring will be pinched from the hammering on the top ring.

Afr got into the 13s when cruising.

I think that might be getting a little lean at cruse in a boat.
Plus you said it got a little hot that will also cause it to detonate.

The tops of the pistons look uniformly black and sooty to me?

I think some of what you're seeing might be from the camera. Look how different the valves look in the pics above and the different color on the pistons from last page to this page

Do the spark plugs have any black spots on them? Is your timing locked at 36?

Crane marine ignition boxes with the built in curve.

The 2 bottom pics at the top of the page most accurately show the color.

I tried to supersize the plug pic but it get blurry. Look for black spots on the porcelain...

Some were uniformly coated in black just like the exhaust ports. Some looked like the one on the right which blows up well. I didn't notice any spots.

If the plugs were idled on it will clean it off. I think I have some plugs and Pistons at home if I do I will post some pics of what I'm talking about... In the mean time what I mean is when you have a nice chocolate looking porcelain with some random black dots on it.

Like you said, a little lean. Doesn't seem like lean enough to kill it. The plugs and exhaust seem to show rich. Water temp never moved. Oil temp got up to about 240.

I don't think I really have black stripes on the side of the pistons from lack of sealing. I think it's more like black scored and scuffed and burned aluminum from scraping the bores where those marks are visible.

This is where a spark plug reading tool with magnifying glass and light can really help. IE: look thru the dark or blackness. By the looks of that picture showing the two middle cylinders on a low quality monitor, I'd be willing to bet you have some aluminum 'dust' (from your piston tops) in there.

I've dealt with many motors that have been too lean while cruising and pig rich at WOT. Some vice versa too. Makes reasing things a little tougher without the right tools and references.

Whats the deal with the adapter plate for the exhaust? Is that the bolt pattern for the 700sci?

I have the old style CMI big tubes. They don't have the necked down pipes/ flange. The primary pipes and flange are too big to bolt directly to the heads

What exactly do you see that indicates that? Although the side of the pistons are physically damaged(not just discolored), the tops don't have any visible damage that I can detect.

Well, it looks like they didn't spend a whole lot of time trying to get the valvetrain geometry right.

I think someone mentioned earlier about oil being baked on to the bottom of the piston? This is the only pic of the bottom I have now. I'll get some more later