You did not mention what the year is of your boat.  If the original engine is 1978 or older then it would be an internally balance engine, whereas the 1979-up would be externally balanced.  If this is the case then be sure to use an external balance flexplate with the 1979-up engine, not the original neutral-balance flexplate (which is for an internal balance engine).

If the 1979 engine is the combo of internal parts that you describe, then I wouldn't change it....except for maybe porting the heads (both intake and exhaust, not just the exhaust).  It should produce about 350 hp with a good tune and Holley 750-850 carb (slightly less with the Edelbrock 750) and turn your impeller perhaps 4700 rpm under ideal conditions.  If you want more power, specifically though the use of more camshaft, then you cannot simply change cams in that particular engine--specific machine work will need to be executed on the heads in order to accommodate a larger camshaft.

Not sure if the rockers I have will fit under the stock covers. I would think you could find some  covers that might accommodate What you want with that exhaust style. There are lots of options. Or you can always find a good pair of logs and snails which is what I have.



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Throw away the stock heads and get a set of aluminum aftermarket heads. That will add a bunch of horsepower as the iron heads are crap.

I don't agree with you, as long as the stock heads are ported they're not crap..

I would really like aluminium heads, but the costs is just too high for this build.



@Steveo909

I will get the heads machined so i can use any roller rocker kit.
Do you have a link to your comp rollers online steveo?


ClaySmith answered with my setup, and that cam i should see about 475 hp and rev 5000-52000 rpm. Sounds awesome to me.


Only thing i am concerned about is the lobe separation which was 108 ....  i have read a lot about "sucking water" because when you have such thigt separation the inlet and exhaust valve is opened at the same time for a little time.
I will ask Clay about that also

Any experiences with 108 lobe separation on wet exhaust here ? 

My boat is a 1976 and the stock motor was from the same year, its internal balanced, and as you say, my "new" motor is a 1979 external balanced... So i need a new flexplate then??
thanks!..

Yes my 79 "new" motor is new build with the newer pistons, and the camshaft i mentioned in the first post.. but i was hoping to put in a more aggressive camshaft...

So you are saying i can't use a camshaft with more lift then the one that sits in my motor just now ?
do i need machine work on the heads for more lift ?

The heads will get ported both exhaust and intake.

Throw away the stock heads and get a set of aluminum aftermarket heads. That will add a bunch of horsepower as the iron heads are crap.

ClaySmith answered with my setup, and that cam i should see about 475 hp and rev 5000-5200 rpm. Sounds awesome to me.

Of course if you talk with ten different cam grinders and/or engine builders, you'll get ten different opinions as to which camshaft you should use in your engine.

If you were to remove the current camshaft from your 1979 engine and install the Clay Smith cam shown above, and add ported D3VE heads/Edelbrock Performer RPM intake/Edelbrock 1410 750cfm carburetor as you intend, you might make 425 hp.  The engine will not generate 475 hp in your boat.  It will not generate 450 hp. It might make 425.  Perhaps it could generate more on a dyno at a higher rpm, but your jet pump won't allow it to get there and you'll never experience it in your boat.  Part of the reason for the unexpectedly low resulting power is the camshaft choice itself, another part is the overall engine combination relative to the new cam (although your newly acquired engine in its current state is a fine parts combination). 

If I were building a 460 engine for a jet boat and stuck with using that camshaft, the build would need to have tubular over-transom headers.  Then the power output might get to 475 in your boat.

The peak valve lift advertised on the Clay Smith cam card is right at the point where it would be highly advisable to machine down the D3VE's valve guides for more retainer-to-guide clearance and simultaneously convert them for snap-on stem seals (rather than the OEM umbrella-type seals).  The OEM pedestal valve train could still be utilized including the stamped steel rocker arms if properly set up with pedestal shims and correct pushrod lengths; aftermarket pedestal roller rocker arms might be a nice upgrade but not entirely mandatory.