1.6 or 1.7 - horsepower difference
 

alright, so i finally got my 331 in and i'll be transfering the heads from my 289 to it which have 1.6 roller rockers on em. the cam is an XE276HR which says it uses 1.7's to make lift @ .544/.544 - but @ 1.6 its only .512/.512

now i have dyno2003 and i've plugged the numbers in as best as i can and with my combination @ 1.7's it should make

422 hp @ 6000 rpm and 400 tq @ 4500 - i swap the lift down to .512 to negate with the 1.6's and my power only drops to 419 / 399

is this right? 3 horsepower is the only thing i'd gain by having the 1.7's in it? the one reason i dont wanna swap is i just blew the 299.00 on the 1.6's and now that i tore the 289 up i wanted to go beefier but they all suggested the 1.7 cam.. so.. if i'm giving up only 3 hp then i should just forget the 1.7's right? or is there something i'm totally missing here..

RE: 1.6 or 1.7 - horsepower difference
 

stick with the 1.6.. no need to throw off valvetrain geometry unless your trying to except more out of a stock cam or something.

RE: 1.6 or 1.7 - horsepower difference
 

personally I'd use what cam manufactorer said to use with cam and as for your desk top dyno calculations.. I wouldn't rely on it's plug and play calculations;)

RE: 1.6 or 1.7 - horsepower difference
 

Kenne Bell says 5.0's make 10 more HP with 1.7's vs. 1.6's. Only that is with a stock cam.............for what that is worth.

RE: 1.6 or 1.7 - horsepower difference
 

i don't rely on the program, just enough to get the gist of it, knowing almost all the dimensions and such of the engine i feel it's close to what it rates it but i don't hold my breath on things like that. i have almost the exacting combination as most other crate engines that are rated at 410hp for a 331 so.. i'll take that too.

just hope it might be enough to hit 12s in this 2800 lb car :)

RE: 1.6 or 1.7 - horsepower difference
 

what kind of heads are you using?

RE: 1.6 or 1.7 - horsepower difference
 

ported performer rpm's

RE: 1.6 or 1.7 - horsepower difference
 

you should hit 12's easy