Marine 273 build

65Val said
Hey, thats neat!...273 in a boat! A lot of your assumptions above are bang on. The "302" heads are the ticket as they have hardened exhaust seats already, and smaller chambers (to help with compression). Does marine fuel have lead still? Since you aren't worried about low RPM torque, I would think you could go with a single plane-type intake, maybe a bit on the "high rise" side for higher RPM use, as opposed to a dual plane (L)D4B style.

...or you could go with a "D-Dart" style build. If you're not familiar with them, the "D-Dart" was equipped with a factory built hi-performance racing version of the 273 putting out 275HP. It had a BIG mechanical cam (not sure if a rev.rot version is available), and 750(?) Holley carb. These were built for high RPM and good power, similar to what you would want in a boat?

Here's Dave Mape's 273 page with a bunch of info...

http://users.erols.com/dmapes/THIRD.HTM

That d-dart package sounds pretty cool! I vaguely recall reading something about it- one of the few >1hp/ci engines from that period, right? Were the only differences between the commando and d-dart the cam and carb?

Unfortunately, the aforementioned cams are literally the only ones available besides the stock grind (which I'm not sure but assuming is at or below .400).

Glad to hear we're thinking along the right track with the 302's.

A single plane (if not too tall) might be a consideration. Low end power isn't he name of the game but we don't rev them to the moon either. The ld4b worked awesome in that ~330hp 340.