Im having a set of FPA headers made, What size collectors do you think I should get? 2.5 or 3" ball? I guess a better question is what size exhaust should I be running? I have a 351, all forged, CHI heads and a Vortech Ysi blower. so will 2.5" be big enough or do I need 3"?

 

well with your combo id get the 3inch so you could have more flow...but if it was just a n/a 351 then id say go with the 2.5

 

hotrod TV did an excellent broadcast on this...if my cobweb memory serves me right, <350hp= 2.5".... 350-450hp= 3"... when you think about it, it makes sense to keep the size down to increase back pressure for improved torgue.