This DIY will show you a way to enlarge the main bearing oiling holes. I take no responsibility for anything you mess up by doing this DIY! Do it at YOUR OWN RISK!

I chose to do this because the hole in the main bearings are considerably smaller than the hole in the block and the hole in the crank. I view this to be a restriction in the oiling of the rod bearings, which seem to spin way too often in these motors. This is just one of the many things I have done to my oiling system, but I am not going to go into detail of that here.

This is not my original idea, I know that ENDYN does this and I would not be surprised if others do too.

You will need the following:

1. Main bearings
2. Good drill
3. 15/64" bit
4. Old or unused main bearing half
5. Spare block
6. Diamond needle files

*Keep your main bearings as clean and scratch free as possible!*

The first thing you need to do is take the main caps off the girdle. I use the two smaller ones for this. Clean them well. You will need to remove some alignment dowels to make this work. Keep the two that will going into the block, look at the picture to see what I am talking about.

Insert a bearing half into the main cap and an old one in the block. I used a new bearing for this that I was not going to be using in my motor.



Place the main cap on the block.



Place the 2nd small main cap on the other one as shown notice there are no alignment dowels in this cap.


Torque the bolts lightly as there are not many threads in the block. I used a little under 20 ft-lbs. Put the drill into the hole and center it up on the bearing. Carefully drill until you go through the bearing.



Now you should be looking at something like this. Notice how much better the oiling hole matches the oil passage in the block now?



Now VERY carefully remove the bearing half. I used a small flathead screw driver under the bearing tab to get it out.

Now take the needle file and remove the burs left from the drilling. You must be very careful while doing this as it is very easy to scratch your new bearings. I put a small chamfer on the front and the back of the hole.



Do not try to wipe the bearing clean or touch the bearing surface while it is covered in shavings from the file! This WILL scratch the bearing and likely embed metal partials into the bearing. I washed the metal shavings off with warm water and then used some mild hand soap to make sure it was as clean as possible.


The finished product:




I would recommend two things: practice an a few old bearings or some that you aren't going to use first and wear clean gloves. I wore clean gloves while handling the bearings that are in my motor, the pictured bearings were practice.