jw454

Hello fellow power boaters!!!! Many of you have heard this story before. I am on the quest for horsepower. I am rebuilding stock 330 HP this winter. Bored out .030 over , forged pistons, 10.5 to 1 comp.ratio, edelbrock performer rpm intake and matching cam (why have I not heard of anyone usin this cam for marine applications?), switched out peanut heads for set of large oval port, new valve springs and 4 angle valve job, roller rockers, carb?, and many other little goddies. Unfortunatley, at the moment, I am stuck with stock exhaust manifolds and risers. It is 4 inch through hull exhaust. Does anyone think I will have a problem with reversion? Cam specs are .570 lift at valve, 240 duration at .050. Any guesses on horse power? Anyone ever modified stock risers to avoid reversion? It is a 20 foot celebrity bowrider weight unknown. Deep V and brovo 1 outdrive. Any advice?? Or opionions? It is also used for ski's and tubes. Thanks for your input.

fred

Talk to Crazyhorse and Dyno, they have a combo that makes great power from the 330 base and it is dependable.....Fred

Payton

Do a search here in the tech section on cams. There has been a lot of good info. Or search on reversion. Maybe you can compare recomended cam profiles with yours.

Crazyhorse

We've used cams similar to the one you picked without any problems, even with stock center-rise exhaust. Can you offer more detailed information on the pistons, such as part number, as well as the casting number of the head you will be using? Here's an example; a SpeedPro L2465F is 10.44:1 c/r with a 109cc cylinder head chamber volume, but with a 119cc chamber volume it's a more reasonable 9.6:1 compression ratio.

ursus

460 hp at the crank @ 5500 rpm would be my guess but,,,

with the performer rpm cam 240/246 on 112 .56/.573 you will have reversion with the stock exhaust and make peak power at like 5500 rpm which is to fast to spin the cast crank. The cast cranks will survive but you have to keep em under 5000 rpm

at 10.5:1 CR you will need to run 93 octane at least and may still have problems with detonation unless as crazy said they are 10.5:1 on 109 cc heads, if you have 119cc heads and they are more like 9.6:1 then you will probably be able to run 93 octane without problems. If you want to use regular then CR needs to be under 9:1

4 angle valve job? heard of 3 and 5 , not 4 in any case make sure they leave a nice wide exhaust seat or you won't get enuff heat transfer and burn an exhaust valve this is why typically marine heads do not use 5 angle valve jobs

For skiing you are probably going to have less torque than you had with the stock 330 with that cam under 3200 rpms

Crazyhorse

We've had really good luck with the cast cranks. Dyno regularly spins his to 5200 and SuperV has been spinning his to 5600 since he's had the boat, and that's 8 years. But neither of these guys runs for hours with the loud levers jammed all the way forward.
If you've got the money for forged cranks that's great, but it's not a necessity for the average weekend warrior. Put a good fluid damper in place of the stock balancer. And try to get the compression to around 9.5 unless you like running 110LL avgas (hey, it really smells cool).

jw454

Thank you for the responses, CrazyHorse, the pistons I first were going to use are SPEED PRO L2465F with pressed pin. I have decided to go with L2399F with floating pin. My heads are 109cc open chamber 1974 truck style, and Ibelieve that gives me 9.4:1 comp ratio. The heads that were on the engine were peanut style with valve rotators on in. and ex. New heads have only rotator on ex. valve. I switched over valves from original boat heads to my new large oval ports. (Valves from 74 heads didnt look so good). As for a casting number Isee two different ones, 336781 and B28-74. if you know anything , good or bad about these heads, please let me know. My 1TON truck, also with 454 and similar set up runs like a bear. ( That engine is 1973). Thank you.

Crazyhorse

Yup, that's a nice piston to use with 109cc chambers. My book says you'll have 9.5:1, and I'd guess about 450 to 460 horsepower like ursus did. I did a 454 like yours for another member, BGIII, and he bought a really nice Ultradyne flat-tappet hydraulic cam from KAAMA, as he had ordered two of them and hadn't used them. You might consider checking to see if he still has the other one on his bench. If he does I'm sure he'd make you a nice deal on it.

formula31

The 781 heads (last 3 numbers are 119 cc open chamber heads. I use them also. I believe they are close to the 049 heads which are the best ovals for marine use. You will have to have the 1.88 and 2.19 valves installed and bowl work at least to get them performing.

Crazyhorse

If they are 119cc you're going to want to use the L2465 piston. They come with pin retainer grooves.