Buddy of mine has an '04 F7 Carb set up for ice racing. He had the motor rebuilt over the summer. It is ported, polished and the heads milled and is only getting 88mph in 800 feet.
Here are the details.... 2 degree timing key, D&D Y pipe, K&N filters, running 35 pilot jets, 490 main jets, running a green spring in the secondary in the far right hole, orange primary spring, 60/40 helix and a 58/50 helix and he has the adjustable cutler weights from 65-71 grams.
It pulls great for 400 feet and then falls flat on it's face turning about 7900 RPM.
Last year with the sled totally stock, he ran 106mph in 1000 feet with 70 gram weights and green & yellow springs with ice chisels.
My question is this, is the clutch not shifting all the way out? He put a marker on the clutch and there is still about a 1/2" of space to the top of the clutch. I think he should be turning more RPM's than this but don't really know for sure. With everything that has been done to this sled, I believe that in 800 feet it should do at least 107.
After talking to a couple of buddies, they seem to think that he should go back to the red or yellow spring and try 74-76 gram weights. Sounds to them as if he is coil binding?
Any and all input would be very helpful!!