connecting rod bearing questions

[madtom]

Sorry if these are newbie questions, this is my first rebuild and I'm learning as I go.

All the main bearings are in and I just connected piston/rod #3 to the crank, when I now see (after reading this about four dozen times in the last week) that it is CRITICALLY important that the mating surfaces of the rod ad bearing are clean and oil free when assembled.

I'm not worried about the clean part and I assembled the mating surfaces without any lube, but I wouldn't say the caps were exactly "oil free". Both rod and cap surfaces had been sprayed with WD 40 the day before and though I did wipe them with a towel, it now occurs to me that assembling without lube and assembly oil free are two different things.
Do I need to pull them, degrease and reinstall? or am I overthinking it.
Thanks in advance for any help at all

[fastEdsel]

A guy I know assembled a small block GM 350 and wanted it put together what he called "sanitary", no lube on any part when assembled. When he started it up, the entire engine lasted about 15 seconds! It blew every rod and main bearing and scored the cylinders and ruined the crankshaft. These or any other engines run in oil. Period. When we overhaul engines we do not touch any of the bearing surfaces but coat them with either lubriplate or STP. I would not recommend WD40 at all except to clean your hands. STP is my favorite, it's sticky and that's fine, it will at least supply lube to the engine on start up if you have no way to "prime" your build with oil pushed under pressure through the oil pressure gauge hole just above the oil filter. Also when you install the rings on the pistons use engine oil on those also rubbing it into the grooves before you push the piston into the ring compressor. Lube those bearings or you're headed for a wreck, that's just the way it's done in our shop. Good luck with your build, you'll do just fine keep us informed.

[madtom]

Thanks for the reply. I did lube the outside of the bearings, but I was worried about the inside surfaces. They weren't lubed, but they did have an oil film. I got worried when I started thinking about the risk of a spun bearing due to not get the back side dry enough.

I ended up taking everything back apart and am glad I did. I found a couple shiny spots and light scratches on two of the main bearings and one of the rod bearings. I had only turned the crank over by hand and maybe a couple of dozen revolutions.

the mains all plastigauged at .001 and the rods about .0015. I think I already know the answer to this, but do I need to toss the scratched bearings?
I woulda sworn everything was squeaky clean, but I guess there was grit from somewhere.

[colnago]

It's important to keep surfaces that you don't want to spin clean of oil (like the crank bearings and the bearing caps), but to lube anything that is spinning (like the crank bearing and the crank). WD-40 is not a degreaser, so don't use it as one.

If you need to disassemble and degrease, it's a small price to pay at this stage. Peace of mind is worth it. I know, because I'm nearing the end of my rebuild, and now I have all of these questions coming up! Did I keep everything clean enough? What did I grease? Did I put enough sealant in the rear seal? What torque converter should I use? Oh, I forgot to replace seal ABC; will it be okay? This second-guessing is endless!

Joseph

[madtom]

Got it. No more WD 40, . I just got it back together and feel pretty good about it.

That said, when you push the thrust bearing and crank in opposite directions before tightening the thrust cap - how much should it move and how do you know if you did it right? I couldn't tell it moved at all, but everything spins real smooth. I haven't checked the end play yet.





-

[colnago]

I don't remember how much it moved when I did mine. Not a lot, but "enough." I do remember that without prying the crank forward/backward, the thrust bearing wasn't in completely straight, and would bind the crank when I tried torqueing the bolts on the cap.

Joseph

[madtom]

I think I must have got lucky, all of my measurements came out and the crank would spin smooth and easy.

I'm about to install the last piston and so far it has gone smooth. Things got kinda tight after #6 went in, but I had the cap on backwards and figured it out pretty quick (shoulda had my glasses on, but they were smeared with sweat, brake cleaner and oily finger prints).

Hopefully this will be my last question for awhile, but I might have a new problem. My pistons and caps were all marked 1-8. However, #8 was stamped with both a 7 and an 8. No problem, I made a note of it.

The problem is, after everything has been cleaned up, I now see that #7 and #8 BOTH have two sets of numbers stamped on them. I'm certain I have the right cap with the right piston. But I can't be sure which was in the 7 and 8 holes.
If I guess wrong, will it hurt anything? I'm about 75% sure of which one is the real number 8, but then again I was about 100% sure that I had all the caps facing the right way the first time, too.
Can anyone help out if there is any way to know for sure which is which?

[madtom]

Got the 7-8 piston sorted out. I took a million pictures of everything as I took it apart and in one of them the #7 stamp is showing clear enough that I can tell for sure which is the real #7. I had a feeling all of those pictures would come in handy.