Thread: Picked up my Son's engine yesterday.

Tweet

Tonight we got a lot done on Dan's motor. Dan and Don finished up filing the rings to get a .024 gap on the top ring and .020 on the second one. While they were doing that I cleaned the pistons and crank in diesel fuel, then wiped them dry. Hardly any dirt came off, and the machine shop said they washed everything before we picked it up.........so I guess they did.

Then we got the crank in and checked the main bearing clearances. The manual says they should be between .005 and .021, which seems like a big spread, but ours came out at .006, so we were good to go. Now the crank is in and torqued to specs. We also lightly scotchbrited the bearings to get the surface slightly shiny.

We were surprised to see the machine shop even tapped every hole in the block, not just the head bolts and main bolts, but even the ones for the oil pan and timing cover. I am so happy I found these guys.

Next Dan and I are going to start installing the rings on the pistons and getting the pistons put into the block. It's starting to look like a motor, and I feel very good about the care we are taking this time around.

Don

Originally Posted by Itoldyouso

We also lightly scotchbrited the bearings to get the surface slightly shiny. Don

And I don't understand this??? Never heard of scotchbrite to a bearing?? Seems counterproductive...

Originally Posted by 34_40

And I don't understand this??? Never heard of scotchbrite to a bearing?? Seems counterproductive...

Takes the shine off which gives the surface a texture to hold a better oil film. Some do, I don't, but it isn't "wrong"

sorry not stepping on any ones toes.. but take it any way you will the bearing are dull out of the box and that finsh is the best to keep hands off

Originally Posted by pat mccarthy

sorry not stepping on any ones toes.. but take it any way you will the bearing are dull out of the box and that finsh is the best to keep hands off

I don't think there's any stepping of toes here Pat! I asked a question 'cause I hadn't heard of this practice. I studied automotive in a trade school, we were taught to protect at all costs the surface of the mains / rods and their bearings. So I was shocked to see someone say they took a scotchbrite pad to a bearing!

Thanks to you and Dave for replying and providing an answer!

Originally Posted by 34_40

I don't think there's any stepping of toes here Pat! I asked a question 'cause I hadn't heard of this practice. I studied automotive in a trade school, we were taught to protect at all costs the surface of the mains / rods and their bearings. So I was shocked to see someone say they took a scotchbrite pad to a bearing!

Thanks to you and Dave for replying and providing an answer!

ok well post 59 is why it was done at one time the flash coating i call it. on the old MIch 77 would be falling off in the bearing box . but there so many bearings now to use and not all made the same some the finsh is machined other are not some are trimetal. bimetal many make up.s of babbitt

Originally Posted by pat mccarthy

ok well post 59 is why it was done at one time the flash coating i call it. on the old MIch 77 would be falling off in the bearing box . but there so many bearings now to use and not all made the same some the finsh is machined other are not some are trimetal. bimetal many make up.s of babbitt

Thanks Again for the answer Pat! 8-)

Originally Posted by pat mccarthy

sorry not stepping on any ones toes.. but take it any way you will the bearing are dull out of the box and that finsh is the best to keep hands off

They are babbitt dull (tin/lead/antimony, etc) but are very smooth. The way it was explained to me by an old time engine builder is that they were too smooth - like a non-honed cylinder wall and that they needed some texture to maintain an oil film. I don't buy that explanation and have never done it. The bearings are manufactured to maintain a certain oil film thickness at a certain crank to bearing clearance and with a certain oil feed wedge. While it doesn't hurt to Scotch-Brite, there is no really good reason to do it.

For a short while I worked in a bearing manufacturing area at GE for a while where we actually cast and machined bearings from a couple inches in diameter to over 24 inches. These bearings were finished on a lathe to a particular finish - and that finish was not really smooth. Many years later, I don't recall what that finish was (125 maybe) and these bearings mostly went into constant speed motors and turbines with minimum speeds of 3000 rpm up to over 6000, usually with 25psig oil pressure and operating continuously for years between inspections. As far as assembly in the field - most service engineers used ordinary STPQuarts of that stuff!!

Do it or not, caution plus a good cleaning afterwards is the best way if Scotch-Brite is used.

Originally Posted by 34_40

And I don't understand this??? Never heard of scotchbrite to a bearing?? Seems counterproductive...

i was going to post on his and threw my post out But i can not leave it a lone .this was something we did as some bearing had a flash for breakin on them and could move. bearing s are much better now no need to still do this.