hello...well it depends on what valve you use, not just size, but how its designed, what port work is done, what port pocket size is used,what chamber work has been done and what head is used>> 194 or 230/250/292...here r a few ranges for exhaust(depending on what combination)from.100-.400
.100 47- 55
.200 90-111
.300 120-141,
.400 144-163
