If you drill into the backplate you might have trouble finding enough thickness for a full thread - it might strip out. Pressure fittings come with a nut that your suppose to use inside the case, but good luck finding room for the connecting rod to pass by it. Usually backplate clearance between that and the rod is pretty close.

How I did mine was this: I drilled the backplate with a drill that was approximately between the proper tap drill size and the major diameter of the treads on the fitting.

I started the hole with a tap, but stopped as soon as there was a chip started and backed it out. This gave something for the brass fitting to start into the hole with.

I then used red loctite and a small socket wrench to drive it into the hole. You can use the fiber gasket if you like but I didn't because I wanted the support of the shoulder of the fitting. STOP as soon as you feel it bottom out or your gonna be sad its stripped out and forced to contend with using the nut inside the case.

After I screwed the fitting in, I stood the backplate inside up on a steel plug that fit inside the backplate to jack it up so I could use a centerpunch to the inside of the fitting to deform the opening and spread the threads into the aluminum, like a rivet. File the brass down almost to the backplate before you do this so there isnt much there to peen outward. Go easy with your strikes when you do this or you could possibly fold over the nipple, and have to start over with a new one. A few light taps are better than one blow in this case.

When the red loctite was cured after a day, I carefully finished filing it flush to the backplate and made sure everything was soaped out good with a toothbrush and used a pipe cleaner also through the nipple.

If you decide not to go through the backplate, the mounting lug will cut down on much of this work, but you better be sure you can drill square into the case first. Tapping a full thread shouldnt be a problem then. The only drawback to this would be "appearance" or "convienence".

In my case it would have been inconvienent due to the stiffness of the Perry tubing and the pump location I had in mind.

Good luck and hope others join in with their thoughts.


P.S. I should have mentioned there are other places on a motor that you can drill such as one of the port runner bulges on the outside of the cylinder, but if you booger it up your left with having to JB Weld the case or replace it. Trying your skills with just a backplate is less costly, can be switched back to "stock" if you like, and prevents having to deal with chips inside the motor from drilling and tapping. If you choose drilling the case, your faced with a complete tear down of it due to contamination of the bearings, ect.