Originally Posted by my87Z
Factory 156 peanut port heads with 195cc intake runners have a max flow of 226cfm at .600 and then 227cfm at .700" and their efficiency rating is 70.8%. The 236 peanut port heads with 208cc intake runners have a max flow if 235cfm at .600 and .700", their efficacy rating is 70.6%.
To put those flow numbers into perspective a pair of 906/062 vortecs with 170cc runners flow about 227cfm at .500" from the factory. These nor the BBC peanut port heads in factory form can support 500hp. A general rule of thumb is that what ever your max flow cfm is, multiply that by 2 and that will give you the absolute max hp those heads can support, and that is with an engine with pretty much 100% VE. Most decent street engine only have about 85% VE. So take the 236 208cc peanut port heads which flow 235cfm at .600, under 100% VE they could make 470hp max but considering most decent street engine on have about 85% VE that number is more realistically 415-425hp.
John lingerfeller's dyno or your math..
I know where I'd put my money..
may he r.i.p.