MTFCA Forum

Good afternoon forum Chums….. I recently spun a bearing on my number two connecting rod………And I’m going replace it without pulling the engine.
I have rebuilt several engines with conventional rod bearings, never with the Babbits so I’m kind of in the fact finding mission phase….. In short any input would be greatly appreciated as I try to get up to speed….Cheers!

Clean the crank within an inch of its life and mike it twice at each end of the throw and then twice at each end 90 degrees out. This establishes how round and tapered it is and gives you the size. Order a rod THAT SIZE, cut especially for you. Get a small container of Yellow Timesaver compound and match the rod to the crank. Properly used, the Timesaver will leave a .0015" clearance. With the rod upside down you can "waggle" it sufficiently through the inspection door to marry the bearing to the crank and then rotate the crank 90 degrees at a time and "waggle" the rod at each of 4 places until you have the same gently-firm resistance on the rod to crank fit. Once cleaned up after this fit, you should be good to go with a well oiled assembly and a startup of the engine. It will seat in almost instantly and be fine so long as it was not left tight.

If you have the experience and know how to use Prussian Blue, you can fiddle with that but if you buy the correct rod, you won't have to scrape anything and at the most, perhaps remove a single shim in the course of mating things up.

I have talked someone through this on the phone...someone who had never used a micrometer, too boot. So it can be done and it can be done successfully. I doubt you'll have much trouble.

Good luck.

Scott…. I’m going out on a limb here but I am assuming that yellow timesaver is the rod bearing equivalent of Valve grinding compound?…. Lol…. I may be giving you a call Sir!
Thanks!

information: https://ws2coating.com/timesaver-lapping-compounds/
what it does and how it does it: https://ws2coating.com/2017/01/30/every ... 0worldwide.
buy some: https://www.modeltford.com/item/TIMESAV-Y.aspx

this stuff has been around for 100 years and is meant to do exactly what you need to do. It is not a modern product force-fit into a role that it was not intended. It is a non-embedding compound which starts breaking down shortly after being put into use, creating a finer and finer grit which will give you a controlled gap if you mix it according to instructions and do not allow it to work so long that it loads up with babbit (keep clean/flushed). You can achieve a 100% bearing fit (or extremely close to it)where even a skilled person scraping will provide maybe 75%. It is as close to "burning in" the bearing like the factory that you can likely achieve on your own. I have used it with custom-bored rods as well as (laboriously) scraping small rods to size and then finishing with Timesaver.

It will come with instructions which if followed will give you a great outcome.

One thing I will add is you must hold the piston somehow when doing up the wrist pin bolt in order to not twist the alignment of the rod.

Kerry wrote: ↑

Thu Sep 08, 2022 6:28 pm

One thing I will add is you must hold the piston somehow when doing up the wrist pin bolt in order to not twist the alignment of the rod.

Excellent point. I have wondered how this is accomplished while installing a rod from the bottom end.

I wait until the piston is back up the bore before tensioning the pinch bolt on the gudgeon pin. Not ideal, but it does give the best support I could muster. Don't forget to pin/wire the bolt head.

Allan from down under.

If I recall correctly (it was a couple decades ago?) ? I stuck a small punch in the hollow of the wrist pin, then allowed it to rotate until the punch wedged against the block, to tighten the wrist pin bolt. A small bolt might work if you don't have a small enough punch. However the threads on a bolt might break under that much stress?
This before pushing the piston back up.

I have never used the "Time Saver" myself. Have wanted to try it for a long time now. I have gotten pretty good with the "bluing and scraping". I think I usually get better than 75 percent!
I don't often admit this, and generally do not recommend it. It requires extreme care and cleaning to get away with it. But I often finish with very fine sandpaper after fitting with scraping-to-fit the bearing. Sand paper is dangerous because the abrasives can get stuck in the bearing material. It can then once assembled and run become a cutter and destroy your crankshaft! As I said, extreme care and cleaning.

Wayne, that is a neat trick. Better than mine.

Allan from down under.

Wayne Sheldon wrote: ↑

Thu Sep 08, 2022 7:43 pm

If I recall correctly (it was a couple decades ago?) ? I stuck a small punch in the hollow of the wrist pin, then allowed it to rotate until the punch wedged against the block, to tighten the wrist pin bolt. A small bolt might work if you don't have a small enough punch. However the threads on a bolt might break under that much stress?
This before pushing the piston back up.

I have never used the "Time Saver" myself. Have wanted to try it for a long time now. I have gotten pretty good with the "bluing and scraping". I think I usually get better than 75 percent!
I don't often admit this, and generally do not recommend it. It requires extreme care and cleaning to get away with it. But I often finish with very fine sandpaper after fitting with scraping-to-fit the bearing. Sand paper is dangerous because the abrasives can get stuck in the bearing material. It can then once assembled and run become a cutter and destroy your crankshaft! As I said, extreme care and cleaning.

Try the Time saver. You will become a convert. I time saver new babbit jobs.
Its real easy to get 100% bearing contact & free rotation with 1 finger.