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The air box mod I did, blocked off the original "snorkel" hole. The bottom half of the original air box was junked. I fabbed up a .12" steel bottom with the square hole cut for the new about 8"x 8" waffle style automotive air cleaner. 4 screws through 2 clamps to hold it. The air cleaner I chose was one that has a more rigid plastic frame and a seal. Even though it is steel, it weighs less than stock lower half of the original. 2 vent lines still plug into the box, but all those plastic tubes are in the trash can. The air flow dynamic acts like a giant plenum and sounds throaty and a bit like a 4 barrel carb on a small block (with the lid not flipped). The rpm range broadened(better flow), it tricks the slides into better and slightly sooner opening since the vacuum in the box is reduced without the wimpy stock Briggs and Stratton air filter. RPM range was broadened and higher where the peak HP is made. Not as peaky with a flatter torque curve. The mods following all played a part in the performance.
The distributor centrifigul advance curve reduced, allowing the initial to be increased, no vacuum advance.
Head was milled like .060 which left the piston to valve clearance a bit tight at .07 and .08. I can't remember the exact compression, but it may be in the notes. I think it's about 10.8:1. The valves are backcut and the bowls are ported mildly. One puck is shimmed, (I don't like that- I was poor at the time), but it ran for ten years the strong use without a tick.
O2 sensor in the header for jetting. It's rich enough to run open headers.
~40 MPG
Without mufflers it will flip backward without popping the clutch at any speed in 1st gear and most of 2nd. Didn't like the Jardines as much as the pipes that are on there. They reduced the rpm at max horsepower. Makes strong power to 5500-9200 without a hitch.
Scott
The air box mod I did, blocked off the original "snorkel" hole. The bottom half of the original air box was junked. I fabbed up a .12" steel bottom with the square hole cut for the new about 8"x 8" waffle style automotive air cleaner. 4 screws through 2 clamps to hold it. The air cleaner I chose was one that has a more rigid plastic frame and a seal. Even though it is steel, it weighs less than stock lower half of the original. 2 vent lines still plug into the box, but all those plastic tubes are in the trash can. The air flow dynamic acts like a giant plenum and sounds throaty and a bit like a 4 barrel carb on a small block (with the lid not flipped). The rpm range broadened(better flow), it tricks the slides into better and slightly sooner opening since the vacuum in the box is reduced without the wimpy stock Briggs and Stratton air filter. RPM range was broadened and higher where the peak HP is made. Not as peaky with a flatter torque curve. The mods following all played a part in the performance.
The distributor centrifigul advance curve reduced, allowing the initial to be increased, no vacuum advance.
Head was milled like .060 which left the piston to valve clearance a bit tight at .07 and .08. I can't remember the exact compression, but it may be in the notes. I think it's about 10.8:1. The valves are backcut and the bowls are ported mildly. One puck is shimmed, (I don't like that- I was poor at the time), but it ran for ten years the strong use without a tick.
O2 sensor in the header for jetting. It's rich enough to run open headers.
~40 MPG
Without mufflers it will flip backward without popping the clutch at any speed in 1st gear and most of 2nd. Didn't like the Jardines as much as the pipes that are on there. They reduced the rpm at max horsepower. Makes strong power to 5500-9200 without a hitch.
Scott
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