Tappet Block Oil Feed Fix

Had I noticed this problem during my winter rebuild I wouldn’t be here posting this follow-up wrench report, but such is life. The problem stems from a difference in the original cylinder block and the replacement cylinder block. The original block has an oil feed line that allows oil to flow from the case into the cylinder block and through to the tappet block, the newer cylinder block doesn’t have this requirement, and therefore doesn’t have the corresponding oil feed setup to match up with the case.  This is not unusual, and I’ve heard it’s common for people to simply block the oil feed line on the case, this would have been a much easier process had I done it before putting the cylinder block back on.

In the picture to the left (click picture to enlarge) you can see the hole where the oil would feed into the block, it then runs through a passage way in the block to the tappets. You can also see that in order to accommodate this, the base of the block comes out at the corner.  The picture to the right shows the new cylinder block in place, you can clearly see that it lacks the part of the base that comes out to match the top of the case, and just on the edge of the block you can see a tiny bit of the oil feed hole in the case.

So with the issue of the oil feed hole being exposed to the outside of the case there is nothing stopping the oil from pumping out and onto the front of the case, not a good thing. As I said, the fix is a simple one, block the hole, problem is that I’ve got the case in place and I’m too lazy to remove it entirely. 

I ended up disconnecting the pipes and undoing the base nuts and pulling the entire top end up about an inch, which gave me easy access to the hole from the side.  I was told afterwards that the rocker boxes should have been removed in order to help prevent damage to the valve train. I’ll do this now that the block is up so that it goes back together safely, and to help get the push rods back in the right spot.

My first choice was to use JB Weld on the hole, thinking that this would block it. This went against some advice I received from both RMH and the Triumph Choppers list, most of the advice I got from there was to tab the hole and plug it by threading in some sort of plug. This would probably be a much better method, but would require me to remove the cylinder block in order to get the tab in there.

So I cleaned the hole and surrounding area to get rid of any oil that might still be there, I mix up a small amount of JB Weld and I place it in the hole, I smooth it over and make sure I didn’t get any where I shouldn’t, and decide to let it sit for the night, per the instructions.  The next morning I went downstairs to check out my handy work, much to my dismay I find that I’m looking at an open oil feed hole in the case, apparently the JB Weld had simply dried and fell down into the oil passage, damn.  I took a look inside and the JB weld has no where to travel, not sure if it’s a change in direction in the passage or what, but it wasn’t going any further down the hole than maybe the centimeter it had dropped, so I took another stab at it, this time putting enough JB Weld to fill the hole down to where the original chunk of JB Weld is sitting. This worked much better, and after a couple days I’ll left with what I have above. At this point I think I’ll pull the rockers off and get the cylinder back in place.

More to come...

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A shot from the manual of the original tappet oil feed line in the cylinder.