stock cammed 310/454 + aluminum heads/intake= ??

[cfm]

As mentioned above, but with a little more detail, your cam is an underachiever even with the stock peanuts.
Mercruiser BBC Flat Tappet Cams
Standard Flat Tappet (oval heads)
Merc#431-4734 / GM#3904359
.004” 287*, 302
.006” 278*, 289
.050” 214*, 218*
.200” 111*, 119*
Valve lift with 1.7 .460” , .480”
ICL 110 ATDC
ECL 118 BTDC
114 LSA
=======================
Will you get 20hp with Eddy aluminum heads and intake ? Sure. More ? Doubtful. They do have smaller combustion chambers (110 vs your 118 or so) and will let it breath over 4k where your stock intake/heads are sinking fast.
You don't have to get a 'big' cam, just something more modern.
MPH ? Not sure. Need to know your present mph, prop, boat. weight, etc to make a 'maybe' guess at it.

[SmokinLowriderSS]

As I stated I will not change the cam.
It would be heads+intake+carb only...
1. I dont like rumpy or high idle
2. I want to keep the rev range down
3. I have an Alpha drive which definately wont like a rumpy or high idle.
I currently have her idling at 550-600rpm so it shifts into gear like butter.
4. I dont want to deal with water reversion problems with the manifolds.
I guess my question would be will I get 40-50hp from just the heads+intake ?
So, my 800RPM idle, with my .565" lift, 280* duration, only mildly rumpy cam, with no water reversion trouble from jacketed through transom headers is out of the question.
OK.
If you have a cam anywhere similar to the .461/.480" x 262/274* that came out of my oval-port (supposedly 330HP, really 280 to 290HP) 454, you are wasting the head money looking for HP.
You may gain a few HP from the heads, and maybe a few more from the intake, but a cam like mine was will be choking any capability you find.
I think you'll be lucky to find 25HP.
Waste of aluminum head $$$.
They'll sure look purdy tho.

[ck7684]

Why not just build up the smallblock?? Are you looking for power or just weight savings?? Throw some alum heads on the 350 and build that for power. Spending the money on alum heads and sticking with that cam just makes no sense...

[HTRDLNCN]

so cam change is a given then for the heads/intake to be worth it..
next question:
does my engine have a roller or standard cam,
how would I know without taking it apart?
I do know it doesnt have a provision for a mechanical fuel pump
(runs fuel pump off the Bravo raw water pump drive) and I think
it was one of the last years with a carb for the standard 454.

[hotbo]

only way i would be able to tell is pull intake then you know.hope it is,be real nice if so.smokin's awful proud of his cam as you can tell well for one thing your boat is not a jet and you put yours in gear it needs to be smooth and it will idle down more than a jet when we load our pump.we can idle up if need be smokin remember that he cant with out grinding away!!!either way you go on cam choice call one of the techs at any cam place they can give you the best advice you are lookin for.prop boats cam different than jets do.imo keep the duration to a minimun and get as much lift as you can.that will help you create torgue. there are all sorts of opinions out there telling you what to do.im really fond of comp cams had excellent luck and power out of several different grinds they sell and had several ones speacil ground for me to my specs over the years.i like comp can you tell

[SmokinLowriderSS]

What year is your engine?
No fuel pump provision (mechanical) should make it a Generation 5 block.
A post '91 Gen 5 or 6 has a non-adjustable valve train.
Also, my cam can be backed off at idle to close to 700 RPM. Cut the duration to 270* and it would idle very sweetly, yet make much more power than the stocker you have. Although, to try to get my lift at that duration, would demand a roller cam.

[HTRDLNCN]

its probably a Gen5,and once I change the heads the valevtrain should be a non issue?
Whatever cam I get has to be able to idle well at 600-650rpm max.
Any higher and it clunks into gear which is bad for the Alpha drive
when its hooked to a big block.
What year is your engine?
No fuel pump provision (mechanical) should make it a Generation 5 block.
A post '91 Gen 5 or 6 has a non-adjustable valve train.
.

[cfm]

Well Mr Lincoln, it looks like 3wood over at SW already did the testing for you. 5-6mph in his boat (older 242 formula) is much more than I would have expected.
This is what's cool about the internet ! Running into someone who already tested what you are thinking of doing.
Speaking of thinking, I can pretty much say all of us above where giving you good /sound thinking. Problem is, in real life most of us have never tested this engine combo because with the $$$ and parts being used we'd all 100% be changing the camshaft also. Anyway, if 3wood is being 100% truthful (I have no indication why he wouldn't be - has nothing to prove and seems like a decent guy) then this may just be what you are looking for, if it's the direction you want to go.
What's the worst thing that can happen ? Needing a cam to put you where you want.
BTW: I believe the Gen VI Vortec head 454's (started to be used in '98?) where the first to receive OEM hyd roller cams.

[ck7684]

How much power can an Alpha handle??

[HTRDLNCN]

Thanks,I just went and read that ..
Sounds promising.

Well Mr Lincoln, it looks like 3wood over at SW already did the testing for you. 5-6mph in his boat (older 242 formula) is much more than I would have expected.
What's the worst thing that can happen ? Needing a cam to put you where you want.BTW: I believe the Gen VI Vortec head 454's (started to be used in '98?) where the first to receive OEM hyd roller cams.