is running a 13t front with a 40t rear to low geared for a 300 foot race. im running 22x12x8 on the rear

Are you spinning like crazy coming out of the hole? I take it you are racing in sand, with 22" rears. I would think you would be tapped out in 5th by the end of 300' with that gearing, but maybe you have the power to rev it out farther with your mods then most people. I would think you would have to start in 2nd gear with that gearing. You will probably be close, maybe just play with it a bit.

im still a little iffy bout that. im not sure

I think with your BB, I would go with a 14 front sprocket. You will have the power to pull that gearing with no problem and not risk having to do 2nd gear starts, and will have plenty of pull in the top end.

I have a friend with a 470 BB kit as well, he runs a 15/35 with 20" tires sometimes and pulls with no problem in short distances. A little too tall for my liking, but then again, it is not my quad, and I am not him.....

i ran the 13t front sproket with a stock 38t with 22inch tires. it ran good i had to start in 2nd but i didnt run out of gears before the end either. the only problem i had was keeping the front end down it would wheelie off the line and everytime i change gears it would come back up