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177.5 HP Improved Stock Arctic Cat F7 Firecat Kevin Castonguay and Dave Lefebvre of The Starting Line Speed and Custom Shop in Waterville, Maine built this 2003 F7 for speed running. |
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TIG Welded Crank Pins John Achramowicz of A to Z Tech welded the crank pins. This unfortunately was not immediately done and as a result after dyno testing the original build, the crankshaft walked on both ends and came out of true. |
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Crankcase Ported The upper case was ported from the reed tips inward following the walls in an upward direction. The cylinders were installed to the upper case half then inverted and blended to each other. Delta V-Force reeds were installed. An offset, 3 degree timing key was installed. |
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Cylinders Ported and Head Machined A degree wheel was set up and the port timing was calculated. Exhaust nozzle at flange area was opened to 49.5 mm and blended into the Jaws exhaust flanges. The main exhaust window was widened, raised 1.25mm, raduised, blended into the port and polished. The exhaust sub ports were also raised and widened 1mm x 1mm. The valves were machined so at full open they are flush with the port roof. Transfer ports were cleaned and matched. The cylinder head was machined. Installed volume was measured and the uncorrected compression ratio was determined to be 13.74:1. |
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Jaws Performance of Manotick, Ontario supplied the full race silenced pipes. To use these pipes it was necessary to re-program the ECU. Because the pipes and porting were suited for 9500 rpms the rev limit had to be removed. The box also had approximately 25% reduction of fuel in the lower rpm range from. The ignition timing was advanced four degrees and exhaust valve open time was made earlier. The 440 SnoPro air box inlet was installed as well as a BoonDockers EFI control box. The box was supplied with special mapping rpm points and was later fully mapped at C&H Dyno of Dynotech Research. The dyno testing resulted in mid 170 hp at 9200 to 9700 rpms with the peak 177.5 @ 9500. BFSC was 0.622 and A/F ratio was 11.50. View VIDEO to see an actual test run.