Oil Feed to Main Galley enlargement
When to do:
For all rebuilds
Modification text:
What we are doing here is enlarging the hole that leads from the pressure side of the pump to the Passenger Side Main Galley.
This is done by drilling it out via the sender hole on the Passenger side of the block, to 1/2 inch, and then drilling just the outside end of the hole up to 37/64 to then tap it for 3/8-18 NPT, and install a 3/8 to 1/4 NPT bushing for the oil pressure sender and/ or live oil pressure gauge feed. The short passage that leads from this hole, to the passenger galley will also be machined out, and all edges and radiuses will be blended.
Pictures:
Lube the drill bit with cutting oil, and drill directly to
1/2". Start with a short bit, and change to the 12" bit after you have
started the hole.
Don't drill to 7/16" first. Go directly to 1/2" This will allow the
bit to take off more material in one shot, and reduce the amount that the drill
bit will "catch".
Once you bottom out with the short drill, then use the 12" bit to finish the hole. Stop the drill bit just short of the cam tunnel, don't break thru all the way into the cam shaft bore.
Now, take your 3/8 ball burr, and cut the square edge off the hole, on both the outside of the block, as well as the inside hole edge, created when you drill from the existing hole in the front of the block.
Here is the "inside lip" that you want to take the square edge off.. also note that the drill is perfectly centered in the original hole.
The drill will bottom all the way out, with the short bit. Always start with a short bit, and finish the hole with a longer one, as it is easier to control the short bit, to keep it centered.
Stop just before you break thru here.
The 12" bit your going to finish that hole with. It does not have to have more flutes on it than this, in fact this "aircraft drill bit" is less likely to break off in the hole, due to it's longer solid shank. When using a bit like this, you just have to pull it partially up out of the hole more often, to clear the shavings from the short flutes.
You can see the end of the bit, as it just reaches the cam bore.. stop here.
Now, with your long shank 3/8 ball burr, go in and take the sharp edges off the holes. Your looking to remove weak points created by the square corners, also to radius those corners, to improve oil flow.
The large hole in the number one main is this size for a reason. The main feed hole does not directly feed the Passenger galley, as the end of this hole actually transfers oil up from the cam area, to the main galley. Go thru this hole with a 1/4 oval burr, and enlarge and radius the area between the hole you just drilled, and the passenger side galley, which is farther up in block, in relation to the feed hole.
If your confused about what you need to enlarge with the burr, this picture should help. Note that the drilled hole from the front of the block stopped at the slot (blue/red arrow), and the actual galley is behind the threaded hole we did in the first modification (blue/yellow arrow).
Now you want to radius all sharp corners, to improve oil flow.
Next, radius the side of the hole in the front of the block, feeds the main hole from the timing cover pressure port. What your doing here is taking the 90* corner out.
And with the square corner of the pressure hole machined off and blended.
To complete this modification, drill the end of the hole toward the outside of the block to 37/64, and tap the hole 3/8 NPT. Install a 3/8 to 1/4 NPT bushing.