Thanks MT that was a very good thread to learn off of. Going to talk with Bob about valve train and lift. Should’ve gotten 2 cups of coffee !!����

You won’t make 600+ NA in full marine trim without sweeper style headers. Manifolds and etops just don’t have long enough runners. Even the 525 has sweeper headers to help with its power. Eickert manifolds would be the only manifold capable but they have long runners also. Don’t know which “builders” you’re referring too but talk to mark rinda at Mer performance or eddie young at young performance. Those are 2 quality guys who will lead you in the right direction to make the best power within budget. Remember budget is the most important. Cheap, fast, reliable. Pick 2

Lots of good recipes for 509's. Endeavour32 purchased a couple of used ones from tinkerer a few years back that made well over 600 hp. I might be wrong but seems like they made just under 650. (Doubt marine dressed and likely dyno headers). Tinkerer would be able to tell you more than likely. Pretty simple builds with dart pro one 310 heads with Dart intakes worked over and set up by Valako. Holley hp 950 carbs and 741 cams. Boat ran very well. After a season I believe endeavour32 swapped out intakes to Brodix hv2000's and quick fuel 1000 carbs and made some very worthy gains on the water. Reliable builds and made great power. Only thing I may have missed was the 1.8's on the intakes.

I'm not certain what they CC'd out at after the heads were ported however I'd imagine around 325. Like I said there are many ways you can achieve your goals but just thought I'd share.

Very important to be sure and have your heads set up properly for marine use what ever route you choose to go.

Only over achievers to people who don’t understand how exhaust runners affect NA power and expect more from a Gil, SM or Etop style short runner.

Thanks for catching my mistake on the intake and carb combo. For some reason I thought you stayed 4150. You did forget to mention your custom made hatch air ports. That boat starved for air after your engine swaps. Makes ya wonder if most consider after almost doubling NA power. When in doubt crack the hatch. lol

the beauty of side opening hatches. Easy to crack for lots of air.