Now the rear housing needs to be modified for the rear water bypass. In its normal form on the 4Ac engine the top water outlet on the engine holds the water bypass pipe in place in the rear pump housing. This is as shown:
This pipe has an O-ring on the end of it to seal it (well known for leaking). Once installed on a 20V the pipe is still needed however it needs to hold itself in, be shorter and also be on an angle to suit the custom top outlet. The most professional way of doing this would be to machine an aluminum pipe of the correct size and get it Tig welded in place. I chose the easier option here and made something out of steel. For this I cut the straight part of the steel pipe off the 4Ac top outlet pipe. I machined up a short section with some grooves in it for sealing (very optional), chopped the original pipe just above where it sticks out of the housing and then welded on my machined section on a angle. It turned out as shown, notice the groove left by the removed O-ring at one end:
This needs to be held in somehow into the original place on the rear housing. For this I chose an epoxy resin. A word of warning though, I used a normal epoxy resin, these are rated at a max continuous use of only about 60 degrees, this is well bellow that of the cooling systems running tempreture. A high tempreture epoxy must be used, I now have my pipe leaking due to the heat fatigue and need to find a way of repairing it, don't make the same mistake! A product that should do the job well is Quicksteel, I will use this when I do my repair. Also when gluing in the pipe be very carefully to make sure that it is in fact in the right place and facing the right direction. If it is wrong it would be extremely difficult to change. A test fit on the engine and then marked out is the only sure fire way.
Here is what my housing looked like when it was complete:
After this is all done the rear half of the housing can be bolted to the 20V front using the steel gasket of the 20V and then bolted to the engine. Seeing the front housing is slightly different it will be slightly off matching the cover of the 20V. While it will still fit it is slightly different but it is very minimal. Here is how mine looked all bolted up:
Off the rear of the standard water pump is another pipe that is needed. It normally is bolted to the back and goes under the manifold and to a rubber hose at the end. This isn't a straight swap as it fouls the knock sensor and quite possibly the manifold brace also. The easiest way around this is to just chop it off approximetly 40mm away from the flange. With this cut the rubber hose can still be used for rest of the chopped section, more on this later. I however chose to chop and re weld the pipe on a different angle, I also had to make a new bracket at the end to support the pipe and it worked out well (got lucky!). I ground and painted mine to make it look as close to factory as possible. I was quite happy with how it turned out: