Wow, a whole area of thought. I had a flange machined on my stock TR4 pully
and then had custom aluminum pulley made and attached it with allen head
screws.. So did Jack Drews....now Jack will have to back to the dyno with
different sized pulleys to find that 8 HP you talk about. :-)
<< The reason to restrict the flow is to increase or maintain the BLOCK
PRESSURE. The block pressure is what eleminates the areas of steam pockets
in the cylidner head that when ignored result in blown head gaskets etc.
Generally about 25 pounds block pressure is a good spot. You will find with
the TR engines that the block pressure goes down as the revs go over 4000
because the system was designed for street use. Therefore the pressure is
going down just when you want it to be working the best. The cure is to SLOW
down the water pump by reducing the size of the driver pulley or increasing
the size of the water pump pulley. This will stop the pump from cavitating
and thus the pressure will stay constant at higher revs. A simple pressure
gage with a line to the drain cock fitting in the side of the block will
give you a pressure number. While testing this on the dyno you could watch
the pressure go from about 15 pounds right down to zero over the rev range
of 6500. By the way you will also get a nice power increase from this little
mod. Fitting Gilmer type belts and pulleys and with a GT-6 engine we had a
power increse of 8 bhp. After that bit of info we did the same thing to all
the engines.
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