Thats true.

If you go with a bigger flat tappet cam, you will push your peak torque and hp into higher rpm ranges and loose lower end torque. The stock cam is good to 5400rpms. You won't gain more than about 15-20hp with bigger flat tappet cam and the only gain will be at WOT. 30-40hp is possible with a roller cam.

I gained about 150 rpm switching from the same cam in my 525SC to a Crane 731 roller.

The boat planes great as of now, what do you think the low end loss might be? I may be able to lose some, but I don't want to make a mistake either..

You can experiment with more cam if you want...it's your choice, but if you're not willing to go with at least a hydraulic roller cam, then the stock Merc 420hp flat tappet hydraulic cam is already a lot of cam for a 454. This is especially true in light of the dual plane intake manifold and the exhaust system you're running, but who knows....you just might get lucky with a larger flat tappet cam. Of course I'm always chanting about a well breathing exhaust system....and so, the first thing I would do is upgrade to a better breathing aftermarket exhaust like Stainless Marine or something comparable. Just my .02....hope it works out for you.

I agree that the exhaust should be the first thing normally, but in my case, I had a bearing spin due to an oil line break, so I had to redo one engine, and since I am doing one, I may as well do both, scored a deal on merlin heads and some other good parts, I am doing hull work too so the exhaust is not in the budget as of now, maybe if things go well I can do the exaust still, I figured at least if I cannot afford the exaust right now I can use mine to boat for the season, at least it will run, the cam thing is mainy just so I don't have to pull the engines again next year when I DO have the exhaust done. I am trying to pay cash for this as I go so the budget has to be affordable.

I would leave the stock cam at least until you upgrade the exhaust.

I agree upgrade exhaust first. If I could do it over I would do that first.
Good Luck!!!

OK, I got a nice exhaust now... stock 496 stuff, everyone has said it will support my engines power easily, I just realized that since I spun a bearing the particles must have went through the lifters too... I forgot about that, so now I will for sure be buying a new cam and lifter set.

Here is the deal, the stock 420 cam that I have now is expensive, 290.00 for cam and lifters.
I have found a few from summit that are 226 intake duration in stead of the 228 that the 420 cam is, should I worry about 2 degrees duration smaller?

Now I am open for cam grind suggestions, roller is still not an option this year, exhaust is not a problem now either, any help would be great!

I have a Crower custom grind in great shape. lift is 561/561 with a 1.7 rocker 594 with a 1.8.
Lobe seperation is 112 and duration at .050 is 229/229 with the hydraulic roller lifters.

I also have a 1998 454 Mag set of heads just rebuilt Ported as far as i would take them. 2.25/1.94 Valves and new springs just freshened. let me know if there is interest.
Bob

I bought a used prop from Bob. The prop was in great shape and he was pleasant to deal with.