T7 440 free air

[Teherr]

I recently traded a friend his low mileage 73 arctic cat 440 el tigre for an invader.  I have a second Invader and wanted to play with a free air T7 motor.  I plan to see what kind of race sled I can make of it.  I plan to pull the motor and go through, but I quickly pulled one head to see how similar the porting looked to an invader.  The head looks just like a 4/6 head, the cylinder porting looks just like an invader.  I understand these motors have a weak center seal, but I could use a invader bottom end if necessary.

Once I get the motor apart I will trace the ports and get dimensions and timing.  The manuals for invader have the port dimensions and timing.  My expectation is they are similar.  I expect this motor is similar to intruder as well.

In theory, with similar race porting, these motors could achieve the same HP.  Limited only by their ability to dissipate heat.  Which of course varies between the free air, fan, and liquid.  I know a race ported invader motor with stock exhaust making 88hp.  I recently saw the dyno chart of race ported intruder produced 80hp. 

In racing, weight matters.  The el tigre I expect is the lightest of the three. 

[sprocket]

The factory race team used the T7 bottom ends they milled off enough off the top of the case to weld on a block of aluminum to put their sno pro cylinders on. On my sno pro that I built I made good power over 100hp. If you're going to run the higher rpms I would recommend using the Hot Rods Kawasaki 550 jet ski either talk with John @ Northern Cranks in Minnesota or Keith @ Challenger in Wisconsin. I have no issues with the center seals. Bill Bune @ Anoka, Mn can also help with just about everything you need done. You will need to make a water pump to make things cool.

[sprocket]

I talked with Keith this past weekend he said he's not interested in building anymore race engines so talk with ther others I mentioned