Lets talk crank shaft assembly process

[macipusy]

Spinning a fresh rod bearing got me thinking deeper about the assembly process and eliminating any root causes of failed bearings from the actual process itself. I disassembled a fresh crank shaft and rod assembly just for observation purposes. I wanted to observe what the bearings looked like after a fresh build.

I have never disassembled these components directly after applying assembly lube. I have only taken the assembly apart after it has been running in the car for a while or for plastigauge verification without the use of assembly lube.

During assembly of the crank and rods in this discussion, I meticulously cleaned the rod bore and back of bearing using a microfiber rag and Isopropyl alcohol. I firmly fitted the bearings in the rod bores and used liberal amounts of black assembly lube (graphite filled) on only the surfaces of bearings which directly contact the crank shaft rod journals. I torqued the rods to specified torque at very small increments to each blot to ensure equal mating of both sides.

Upon dis-assembly of the rods I found assembly lube on the back of all bearing surfaces which mate to the rod bore. I am assuming the grease made it's way under the bearings during torquing of the rods, before the bearing was fully tight in the bore.

This is of concern to me, having a lubricant on surfaces which could potentially spin and cause failure.

Should I be concerned with this? Thoughts? Possible process suggestions to prevent this from occurring. Maybe this is no big deal and I'm OCD.

[Legacy777]

That is very interesting observation. Was the assembly lube on the entire back of the bearing or just the sides?

Were the bearings seated as best you can against the rods & caps?

I have never disassembled a freshly installed rod like that to see if the assembly lube has made it on the back side or not.

[macipusy]

There was definitely compressed grease under the bearings. A thin film, but observable shiny residue and noticeable to the touch. I even wiped off all grease off the rod before pulling the bearing out, to make sure it is not contaminated during dis-assembly.

I seated them by pressing down on both ends and then in the middle. I'm considering on seating them dry by torquing the end caps on just the rod and bearing itself, off the crank. Maybe even using less assembly lube.

The video on you tube of the guy assembling the ej257 in his driveway, he just douses oil on the rod with bearing installed. The oil is definitely breaching under the surface in that process.

[Legacy777]

If you have the patience to do some more testing, I'd do like you suggested and seat the bearings dry, torque the end caps without installing the rods, remove the end caps, apply assembly lube, install & torque rods on crank, and then disassemble for inspection.

If you go through all that and still have a little bit of lube behind the bearing, the best conclusion we can come to is that it's normal to get some assembly lube behind the bearing.

[macipusy]

I tested a revised assembly process last night.

Original process was as follows:
Cleaned all surfaces with microfiber rag and alcohol.
Wiped surfaces with dry microfiber rag.
Inserted the bearings by hand and seated by hand.
Applied 1/4" diameter bead across the whole bearing.
Installed rod on crankshaft.

Observations:
The excess assembly lube squeezed out around the edges of the rod.
Upon removal of the bearing from the seat, 85% of the underside surface was coated with assembly lube. Only about 15% of the bearing surface to rod seat was dry on dry contact.


Modified process was as follows:
Cleaned all surfaces with microfiber rag and alcohol.
Wiped surfaces with dry microfiber rag.
Inserted the bearings by hand and seated by installing end cap and torquing to spec
Uninstalled the cap and spread assembly lube on surface of bearing (just to coat the surface, similar to the process I use for applying Fujibond).
Installed rod on crankshaft.

Observations:
Not much assembly lube was observed squeezing out the sides of the rod.
Upon dis assembly, 99% of the underside of the bearing was dry. About 1% grease found it's way under the bearing. A tiny bit near the bearing to bearing seam and a very little around the circumference, but did not breach more then 1 mm from the sides.


Super happy with the results of the modification to the assembly process. I think the combo of properly seating the bearing to reduce the gap between bearing and rod seat coupled with the reduction of grease solved the root causes of the contamination.

[Legacy777]

That's good to hear the new assembly procedure got the results you wanted!

I'm curious if that lead to your failure or if it was something unrelated. I say that because once the engine is started and oil is flowing, it's going to be everywhere, including behind the bearing....there's no way it will stay dry. Anyway, hopefully the new process will at least give you a little better peace of mind.

[86BRATMAN]

Your new modified procedure is how I was told to assemble engines by an old time engine builder about 16 years ago when I was rebuilding my first motor. I've always done it that way, and knock on wood, I've never had any issues with the bearings. I hope this new build does well for you.