so i have 3 spare housings that are junk and i wanna try and PP port them. im going to just cut the holes with a drill press since the housings are junk anyway. but i wanted to practice welding and fitting the tubes.



i have this link, but have a question - http://www.rotaryeng.net/Welded-steel-p-port.html - what about the outside? does no need to be welded?



i also wanted to try and use the aluminum tubing like most people use. do i weld it to the outide only? or the inside too? really, im just wondering where to weld.

 

You have to use a stainless tube if you plan to weld it to the rotor housing like that. Aluminum tubes are typically a press fit and sealed with epoxy in the coolant passage, but not welded.



I wouldnt count on a hole saw making a good enough cut for a press fit. A milling machine and a boring bar is the proper way to size the hole.

 

these are just for practice. and none of the 3 rotor housings are usable. so im not going to spend money on getting them machined out.



so how do people get the insides to look like the metal is one without wleding the aluminum tubing???

 

just machine and fit.

 

A 0 clearance press fit. You cant get that with a hole saw, you need a boring bar in a milling machine.

 

Yeah, most holesaws tend to be out of round so the holes will end up oval.. And most drill presses have way to much walk in the quill to get anything resembling accurate.

 

The pictures are of a test mule Pport for building airplane engines from Paul Lamar's web page. A very good page for rotor nuts.



I do not agree with the welding idea. I see no advantage at all, and I see a chance to end up with an un usable paper weight, and I already have a nice sized pile of those. The liners are probably of cast nodular iron, and can and od strtetch a bit which is required if the weld zone is expected to not crack open as the weld cools. The weld is right where you need no surface anomalies to screw up the apex seals. Very good work with a die grinder is required to save the housings after the weld.



Some things I have noticed over the years.



Rotor housings are flexible as though made of rubber. They only lay out dead flat when clamped between flat pieces of iron.



Welding anything makes it smaller in the weld area. Less than perfect rotor housing finishes make apex seals unhappy.



No matter how good you are with a die grinder, if you do not protect the area near where you are working, you will eventually, hose a perfectly good housing. Make a steel sheet mask for the port. Or put 8 layers of racers tape around the port.



An aluminum tube for the Pport runner would closely mimic the expansion and contraction of the housing way more than a steel, or stainless steel tube. The specific tube material would not matter so long as it is aluminum. I used Devcon plastic aluminum for the same reason. No welding on either end of the tube. A hole saw would be fine. Not even a light press fit

is required. Better a slightly free fit. When the saw is about to break through, go very slowly, and keep the oil going into the hole saw. Protect the surfaces.



A thin wall tube would require far less smoothing around the port face. Keep the tube ends just below flush with the liner.



Less is more in Pports. The big rectangular ports work best right up to 11,000 RPM. Not much fun down low however.



Less than 2" ID is plenty for the street. Minimize overlap. The engine in the picture had 250 HP below 7,000 RPM.



Watch the tach the first few times out. The engine will not quit pulling. If you wait for it to nose over a bit before you shift, you will be over 10,000 RPM headed for the moon. Get a rev limiter. Keep the EGTs under 1650 all the way up. Lots of fuel will be needed.



Leave about 2" of tube outside the housing. Enough to get two hose clamps installed. A support rod, as in the picture is required the keep the TB or carb from shaking to death.



Save the diff........use old hard tires.



Lynn E. Hanover

 

we hear the old school guy around here uses a hole saw to do the PP, i would think you want the smaller size on the inside, cause hole saws are BIG. also that way you can port it the same.



although he probably just cuts it with a hole saw, and shoves the pipe in there...

 

what wall thickness aluminum tubing is reccomended?

 

It only has to be thick enough to prevent collapse when the hose clamps are tightened. So

1/8" (.120") wall would be the minimum.



Lynn E. Hanover