550 HP should be easy. Just went through the same thing.

- Stainless Marine Manifolds (these were already on the boat)
- Rectangle heads with stock valve size and a valve job (matched to intake NOT ported) with Performer RPM intake and 850 Holley 80330 vacuum secondaries, one jet size down on secondaries
- Converted Gen V 502 Block to roller, honed only not bored -- Bob Madera (RMBuilder) Custom Cam
- Stock JE700 pistons with new rings, stock rods.
- 9.25:1 compression up from 8.75 (.010 off the block and .010 off the heads)
- 1.7:1 Scorpion Roller Rockers

539HP and 562TQ full dress with wet exhaust. Peak power was ~5100

I am sure I left some power on the table -- I specifically told Bob this was a family boat and drive-ability and good idle characteristics were the priority -- he is the man and should be your FIRST phone call, he was EXTREMELY willing to work with me to get the RIGHT combination. He is the cam guru but will help you through the whole process.

I fought this a bit when I almost went with a stock hydraulic flat tappet and I am SOOOoooo glad I talked to him. If you already have a roller motor it won't even be that much more expensive.

http://www.marinekineticsonline.com/

yes my motors are rollers

They know something about carburetors:

http://www.holley.com/applications/C...bSelection.asp

wow crazy according to there calculator an 8200 rpm 358 and a 5400 rpm 511 both require an 850.......... must be something to that air/fuel/hp relation.
brivander thank you for the info on your motor, that is the type of helpful info i was looking for

With premium gas, you have a little hotter cam and a little more compression, 575+ horsepower should be a no-brainer.
Good Luck!

thanks! let ya know how it makes out gonna be a little while prob wont finish them until march or april

Bob designed my 439 C.I. BBC and I would strongly urge you to use him for your cam set up at the minimum, you will learn a lot from him. My little engine made 525 hp and he had ProSystems design the carb for it. It was a holley HP 950 with a 750 base plate. Flowed at 830 CFM. If I were you and if your going to buy a new carb have Patrick at Pro Systems build your carb. It will be built for your engine and its roughly the same price as a carb from Summit. Good luck with your build!

Sounds like a pretty cool package, post some specs, I'm curious. Compression etc.?

I can idle at 675rpm, IN gear...but like I said, I use this boat for a LOT of family activities so I needed something a little tamer, just a glance at the specs and you wouldn't believe the amount of lift he uses and have it run so tame. He knows his stuff. Bob is no joke, he's the man.

According to that Holley link, a mildly modified 454 (mild perf cam, stock heads, etc) turning 5100 rpm max (ie, a 454 MAG) should have a 650 cfm carb. Even Merc didn't go that small, the stocker was rated 750 cfm.

I ran my 590HP 468's through Holley's calculator and it said anywhere from their 850cfm to a 1050cfm Dominator. That narrowed it down. LOL