I race a 250xflow in street stocks and i am trying to find anyone who has any imfo on xflow heads. I am trying to find out wich head belongs to wich motor. My motor is bord out 40 and 60 of the head wich is a open chamber head and i have a 892 andrews cam. the power range i need is from 2000rpm to 5500rpm over 100meters rolling start wich im not geting.I have a 4 speed box raceing in second gear ratio 1.99 and diff ratio 1.77 with 205/65/14 tyres. Most of the cars i race against are xf falcon apart from a few v6 holdens sigma but the xf beats all of them im only haveing trouble keeping up with other xfs.Now this is why im asking about the heads as some of the drivers swear of the closed chamber heads with smaller valves. I have a selection of heads e1 e2 ect but dont no wich head is best or what motor there of. The motors have to be cept standerd as no porting pollishing or bigger valves allowed. I hope theres someone out there that is a ford man and can help. Cheers.

Heads: there are earlier C1 and C2 heads that have more 'meat' in the chamber creating a higher compression. C2 is the better of the two. As to valve sizes etc on these heads - I'm not sure if they are bigger or not.

Your biggest problem from what I ca