Hey guys, I'm new to the site and may not be in the right company to ask this , but here goes . I've been reading some of the posts and see there is a lot of BBC knowledge here . I have a '95 Cobalt 220 bow rider, 7.4 GL , Volvo penta Duo Prop O/D . It's a 330 horse peanut port engine with cast iron intake and Holley vac. carb . 440 hrs and in mint condition. Ran a comp. test and all were 145-150 psi . motor is still strong and runs clean. Now for the 64 dollar question. This winter I want to build a bit more power for the main reason that I keep a good number of people onboard , plus I just like to pump things up .
How much increase can be expected going to a set of 049(large oval) open chamber heads , opened up to 2.19/1.88 valves with pocket porting and a Weiand/Edelbrock intake with a better carb . I would like to start with a good set of exhaust manifolds or headers for this mild combo that could be used on a hotter 468 in the future . I've already got the through hull exhaust . I'd like to see 360-380 out of it at around 4800 . I don't know the cam specs for the 330 horse , but I believe it is an 8:1 CR engine , so it can't be very hot . Where can I find the specs on this cam ? Would there be any benefit going to a different hydraulic grind marine type camshaft ? Roller rockers? What exhaust system is good for this type boat?
I run timing at 10 initial , 34 total using a stock HEI with no vac. adv.. This seems to be a bread and butter engine with plenty of potential for some gain. Any tips for a new boat owner would be great. I've been rodding since I was a kid , so I know plenty of street antics , just don't know how much I can get away with in the boat before I have a slug that won't pull an inner tube . At the moment this rig runs just over 60 @42-4300 with two people in it and jumps on plane with no problem.
Question #2 , and I am leaning this way for some reason. I have a 2 bolt 454 truck engine ready to be bored .060 for a set of TRW L2349 LS6 pistons . These are listed to bump 10:1 with the open chamber head . I already have a new set of these pistons , so that's all I'm considering , other than a set of cast flat tops . Gotta stay on budget here.
Using this marine camshaft :
INT.323 .549 293° 232° 12° BTC 40° ABC 88°HYD104°8
EXH.328 .558 310° 239° 56° BBC 3° ATC 116°
Or a Comp Cams 292 magnum hydraulic camshaft . I already have this camshaft and new lifters, so no more money spent on that.
FLAT TAPPET: Street/strip applications. 10:1+ compression, 3000+ stall or 4 speed. 4.10 or lower gears & aftermarket intake. Very rough idle.2500-650011-213-3292H244244.550.550110°
My thoughts would be to leave the 330 horse intact, stored tight with MMO inside her and just build the 10:1 468 for playing with. When it's time to sell the boat , drop the 330 back in it and put the 468 in one of my Chevelles .
What's the best option of these two ? Sorry for the book . Thanks for any help in advance .
Here's my rig .