I'm looking at building my efi 351 with a 408 stroker kit, gt 40 heads, long tube headers, edelbrock performer intake manifold and a large cam. Can yall tell me about how much h.p. and torque gains i can expect? Just an estimate, cause i have no clue.

 

GT40 heads on a 408? Not ideal by a long shot so it'll have the same HP potential as a 302 does with them... or about 300hp. The difference will be that it takes 6000rpm for the 302 to get there while the 408 will make it happen at 3500rpm. TQ is where you'll see massive gains, The 408 will make 400 ft/lbs from idle and maybe close to 500 ft/lbs from 2000rpm and up, and in comparison the 302 TQ peak will be 350 ft/lbs at 4500rpm

 

alright, so what heads would be best?

 

and what kinda numbers do you think i'll get from them?

 

You will want a 180-190cc head like the cast iron RHS or DART heads or aluminum AFR or RHS heads, and all of these will make 400+ hp and 500tq... depending upon the cam selected of course and assuming the motor also has an appropriate intake and fuel system..