where to drill for perry pump
 

hey guys, i have a super tigre G-90 and bought a perry pump regulator for it. the instructions for the the pump say to drill and tap a hole for the pressure fitting either in the center of the backplate or through the engine mounting lugs. i just wanted to know where the best place to drill the hole is.

RE: where to drill for perry pump
 

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.

RE: where to drill for perry pump
 

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I have drilled and tapped holes in the center of the backplate. I did not use a nut on the inside and I had no problems with this installation. I've done it four or five times on various brands of engines without a problem.

However, later on I began to use pressure fittings either from the engine manufacturer that were the same size as a backplate bolt, or I increased the size of the hole and threads in a backplate bolt of a metric engine to accept a 6-32 pressure tap used for muffler pressure on tuned pipes and mufflers.

I presently own a used HB.61PDP that someone drilled a hole into and through the right hand (doesn't matter which side) engine bearer. This is a good idea if the other two methods aren't easy for you. I imagine that if a backplate screw hole isn't already vented to the crankcase and if the backplate material is too thin (Webra/Super Tigre), the engine bearer location might prove to be the best. But you won't do this drilling job with a hand drill. <G>

I would try to find a way to use the backplate screw hole first.

RE: where to drill for perry pump
 

looking from the back, the left upper backplate hole is drilled all the way through to the crankcase. This is on purpose to use it to fit a pressure tap.

RE: where to drill for perry pump
 

You can use the nut on the outside of the case as a jam nut to prevent the pressure tap from unscrewing. I dont' think the nut is intended to be used on the inside, but I could be wrong.

RE: where to drill for perry pump
 

It is easiest to drill and tap the center of the backplate then put a drop of LocTite on the fitting and screw in firmly. Then whack the excess inside with a Dremel. No problem.

RE: where to drill for perry pump
 

You CAN'T use a nut on the inside.The con rod will hit it. We used crankcase pressure for control line combat and rat race for years. You drill and tap a 4-40 hole in the backplate and screw in that size pressure fitting and then file it flush on the inside. Fox used a pressure fitting on the upper backplate screw. The one that is behind the bypass. That hole went straight into the bypass. The pressure fitting replaces the backplate screw.