im trying to decide what i want to do. im on a tight budget and at the moment i currently have a complete l31 carb vortec engine with forged pistons and a comp xe270 cam .010 ground off the crank and heads. i want more power. so should i build the 406 or throw a set of afr's on the 350? i have a 400 block that i wanna get started on.
I say build a 406 with AFR's cause the money will be well worth it in the long run it also depends on how much power you want to make but im bias cause im building a 406 with AFR 210's with expected 550HP N/A for the street. There is no replacement for displacement.
Cubes are good no matter what your goals are, unless your goals include serious mpg #'s. I'm building a 406 with Trick Flow 195's. I'm looking for the most power I can get with "0" drivability issues. A big cam acts smaller with big cubes. Same power, just better manners. Same thing with better flowing heads, intake, and carb. If you already have the heads, "storing" them on top of the 406 would be a good place to put them. That way, you always know where they are and you aren't apt to lose them.
Well you need the heads either way.. heads make power.. Vortecs on a 355 or 406 will be a bottleneck either way... heads make power.. There is a replacement for cubes... it's rpm..
Heads...more cam/rpm... A 355 with the new 235's might sound like overkill but it will scream with the right cam. On the 406, I'd do nothing less than the 235 Eliminators.. Not hard to make 700hp with these new heads.
The Vortec's flow pretty well for a stock GM head. I would rebuild the 400 and get the Vortec's drilled for steam holes. Use these heads until $ permits the purchase of a set of AFR's. Super Chevy or one of those magazines did a build up on a 406 using Vortec's and it made something like 470 hp and 500 tq.
Give AFR a call once you get close...excellent customer service and they will steer you to the right choice for your application.