509 Brodix BB1 CNC 260*270*@.050 .680" lift 112 lsa 9.5:1 compression 715hp @6300 rpm. Motor kept making horsepower to 7400rpm where the pull was ended because the desired rpm in the boat was 6300.

540 Merlin steel 320 525efi cam 9.5:1 650hp @ 5500rpm 630tq. No need to spend $3000 on a set of heads when $1,000 set of heads will do. For that matter with 540 ci's if 650 was the goal a GM steel head will do. If you want to spend $3000-$4,000 on a set of heads 750hp is a better target than 700hp.

Thank you for the reply black baja, those Brodix heads are the ones my builder recommend. Would either of those heads still work good on a 509?

Pretty sure that mpi will need a bunch of help to get much HP over 600, ( Smitty ) on this board has done a bunch of dyno testing with these intakes, might want to send him a pm and chat,

Are the Merlin 320's a good head for a 509ci? 650hp is my goal, trying to make my drive last a season without having to build it too.

I wouldn't use the merlin heads.but if you already have them.

That is so strange I was just reading up on those last night. How strange... Was wondering the same as you posted. Lol

He's gonna tell you the exhaust port is prolly to big and lazy. Lol. If they are what they claim my opinion is they would be an awesome head. Would love to try them on a bigger cubic inch engine.

I'm building a pair of 555/565 (undecided) and am aiming for 700hp plus at or under 5,700. Build so far is valokoized pro 1 310's, edelbrock sv-565 intake, 1050 dominator and unsure on cam however have two new billet 244/248-644/648 on a 111 custom grinds. I'd like a little more lift. Compression will be 10.5:1.

Just an FYI Gellner Racing was punching out 540's with virgin pro 1's, dart intake, 4150 1000 cfm Holley, same cam as above and making 650 around 6k rpm. Would make much more power with head porting and a little intake work.

So what is a good solid performing head for $1500-$2000 a set? Would I be better off working over the stock heads that were just rebuilt?

Interesting. One would think the SV565 would have too much cross sectional area for a low rpm 555/565.
looks like I'll be doing some digging on this.