ok here deal 255 formula twin 454,s under 10.1 compression basically stock rebuild with aftermarket intakes carbs ingnition system running peanut port heads for now upgrade later using center dump cast merc manifolds and thruhulls picking between 2 cams im more after mid range power and top speed

heres the 2 im thinkin about what you guys think


Hydraulic flat tappet



Basic Operating RPM Range


2,500-6,000



Intake Duration at 050 inch Lift


228



Exhaust Duration at 050 inch Lift


238



Duration at 050 inch Lift


228 int./238 exh.



Advertised Intake Duration


286



Advertised Exhaust Duration


296



Advertised Duration


286 int./296 exh.



Intake Valve Lift with Factory Rocker Arm Ratio


0.540 in.



Exhaust Valve Lift with Factory Rocker Arm Ratio


0.540 in.



Valve Lift with Factory Rocker Arm Ratio


0.540 int./0.540 exh.



Lobe Separation (degrees)


114


or option 2


Hydraulic flat tappet



Basic Operating RPM Range


3,000-6,500



Intake Duration at 050 inch Lift


238



Exhaust Duration at 050 inch Lift


248



Duration at 050 inch Lift


238 int./248 exh.



Advertised Intake Duration


296



Advertised Exhaust Duration


306



Advertised Duration


296 int./306 exh.



Intake Valve Lift with Factory Rocker Arm Ratio


0.540 in.



Exhaust Valve Lift with Factory Rocker Arm Ratio


0.540 in.



Valve Lift with Factory Rocker Arm Ratio


0.540 int./0.540 exh.



Lobe Separation (degrees)


114

Between the 2 I would say the first one, and it may be too much.

I think that both are too big with peanut port heads.They can barely flow enough air for a 454 to turn 5000 rpm. Been there , tried it. I would be thinking about something along the lines of 218 degree @ .050 for the intake, and 224 to 228 degree @ .050 on the exhaust , with about .500 lift.and a lobe separation of 112 to 114 degrees. Or you can call Bob Madera at Marine Kinetics and he can tell you exactly what cam to use to hit it right on the money the first time. Just my .02.

+1 Bob Madara 585-654-8583

find a couple of sets of 781 oval port heads. usually about 300 a set. you don't want to buy an aftermarket that won't match up to the peanut ports. BIG turbulence in intake path. and you also don't want an aftermarket intake that will match the ports, cuz nobody else will want them later.

X2 on calling Bob Madara. As to the rest of your build scrap the whole project! 10:1 is way to high for iron heads. 10:1 is pushing the limit for aluminum heads. Second peanut ports are only good for a basic 330 hp engine, don't let anyone tell you that you can make 500 hp with them. You can't! Third, the exhaust CANNOT be used. You cannot run it temporarily, with the cams you selected you will surely have reversion and destroy your engine in quick order. Last, the cast internals are good to about 5000 rpms after that, you're on borrowed time.

You have basically two choices, do it right or don't do it! If you on a tight budget, ask around on here for some low hour used engines. To build your engine right your going to have at least $5-6000 (per engine) and thats finding some killer deals on things. The 330 engine is a terrible engine to build up, I just sold both of mine becuase of this. All the internal parts are cast and wimpy! If you can't afford a couple of take outs then install a 454 mag cam.. The peanuts should be able to flow enough and you can also use the stock exhuast. Good luck!

I totally agree!!!!!!!!!

gee i just asked about cams opionions on both i listed to big or small would work

i never once said im looking for 500 hp dont care what hp they make
i also said under 10.1 basically stock rebuild with a few add ons dont see nothing race about that

im not pullin 330,s out and uping them im starting from scratch as far as 5-6g each far from it
i dont have about a quarter of that in 3 complete 454,s good runner auto cores my exhuast intakes etc
ill prolly have 4-5g total in both once refreshend and boat ready

i used to drag race nitrous cars so if i wanted to go crazy they would have h beams forged pistons aluminum heads big roller cams dominators etc this is far from that like i said basically stock rebuilds with good used upgraded parts besides cams
im reusing the peanuts as thats what i have and there fresh and i have intake already

also curouis why you think you cant run over 10-1 with cast heads? with air fuel timing correct whats the problem

You've been given the correct answers. Its your choice what you do with the information.

The biggest cam you can use with stock Merc center riser exhaust is something very close to the stock Merc 454mag which is .510/.510, 220/220, 115.5 lob sep. Any bigger and the overlap will suck water back into the cylinders.

If everything is dialed in perfect, you might be able to run 10:1 with 93 octane.....or they might just melt a valve, detonate or burn a hole in a piston.

A 9-10 second WOT run down the 1/4 mile is nothing like running for 10mins at 4500-5000rpms.

I have a 468 with cast internals and stock exhaust and I run a Isky 270/280Mega
http://www.flatlanderracing.com/iskycamsmarine.html

But I do have 188 rectangle port heads. I have no reversion issues. Cam made peak power between 5000-5200rpm on the dyno and then started to fall off after 5200. Which is perfect because I wanted to only spin the engine to 5000rpm with the cast internals.