I’m looking at using a set of Dart Iron Eagle 308s on a mild pump gas 540 NA fresh water lake motor build. Max rpm 6000 with lots of cruise in the 4000 rpm range. Shooting for 650-700hp. Reliability and durability is most important over big numbers. I’ve read several times that people state in stock form, they don’t flow very well? Anyone have firsthand knowledge? I’m wondering if it’s just cleaning up the bowls, guide boss and transition to the seat or much more in-depth short side and deeper port work? Anyone care to comment ?

IMO, 308's are too small for a 540ci with your power goals. Something more in the 345 range would better

Mostly attracted to the Darts being cast iron (lower corrosion issues) and thought that the smaller port size would preserve low and mid range torque.

Doesn’t answer op’s question but Dart did offer a 330cc CNC’d (intake and exhaust ports) Iron Eagle head.

Also pretty sure JIM V (Valeko) has ported the Dart iron bbc heads.

It takes a really, really good combo for a marine 540 to make 700hp. Most of them dyno around 630-640 from what I have seen. I don't believe you will get there with those small iron eagles unless you really up the compression.

I got 620hp out of a 502, dart 308 heads, 741cam, merlin intake, 850 Aed carb. I very pleased with the outcome of my builds. A friend had 540’s built and they dynoed at 690.

I did a similar build in 2017 but was a 548 with 088 heads that had minor bowl and intake work done. The cam was a little bigger than a 741 but not much. Motor had around 10:25 compression as I normally run at higher elevation.

. A friend had 540’s built and they dynoed at 690.[/QUOTE]

What heads and compression ratio?

Do you have a heavy, slow hull that drags thru water hard or a zippy , stepped hull?

I believe BenPerfected has a couple sets of Jim's ported 308 Darts and he made 800HP with his 502's. But, remember these engines are a meticulous build. I'd say they are "Above and beyond builds" and raced engines.