496 Stroker - Help me with a reasonable build
 

I'm looking for advice regarding a practical build for a 496 stroker. Kind of a long post but I need some practical advice.

What's important to note is my application for the engines are somewhat different in that they will be used in a larger inboard boat. The engines will be built for torque and not high HP or high rpms. In fact because of prop limitations the wot rpms will around 4800. I'm looking at somewhere around 450 hp and 525 lbs of torque. These engines will never be runned at wot. They will be doing a lot of idleing and cruising at a max of 3800 rpms, but they do push a heavy load.

After reading this site and speaking with builders the stroker was the way to go so I started to get bids. This is were I need some advice on the practcal side. I've gotten some bids with all high end componets and all forged internals because that's the way I thought I had to go. Of course the cost reflected all that and it was in the ozone. After some more discussion a couple builders took into consideration my application and feel that it might be an over kill for how the engines will be used. They feel a good cast steel crank would be important but I could easily scale back from there. After all I'm not building a 650 hp stroker at 6000 rpms. It was noted to me that my current engines are all cast and provided good service plus the newer 8.1 496's were mostly cast and hold up just fine in a boats like mine.

I would like to come up with what's really needed and practical for my application so I get apples for apples bids. What do you guys thinks is absolutely needed as far as internals and what heads would you lean towards. The blocks are Gen IV's.

You guys have been a great help - Thanks

What is the boat? Make, model, length, weight, drive type ect....

The boat is a 1988 37 foot Wellcraft Cozumel sportfish bridge. It weighs 21000 lbs. The current engines are Crusader gen IV 454's and the transmissions are Borg Warner 72C. I normally cruise those engines at 3400 to 3600 rpms. With the strokers I will be able to reprop and get a bit more performance. Hopefully be alble run between 3600 to 3800 also. I know the more the boat gets out of the water the better the fuel economy even though I'm running a bit hotter.

Hope this helps.

To be more specific, this one of the builds I'm considering. Will this be reliable for my application or is there some major weakness that I must address? Suggestions? Looking to get about 425 -450 hp with 500 -525 lbs torque keeping wot rpms under 5000.

Cylinder Heads:
OE Large Oval Port heads
3 angle competition valve job
New Head Bolts

Rotating Assembly:
Speed Pro Hypereutectic Coated pistons 9.5:1 CR
Eagle I beam Rods w/ ARP bolts
Eagle cast Steel Stroker Crank
Balanced rotating assembly within 1 Gram
Speed Pro Moly Rings
External Balance


Valve Train
Comp Cam custom grind flat hyd
Comp hydraulic lifters
Hardened locks and retainers
2.19 Int / 1.88 Exh stainless valves
Comp Springs 1.540 OD
Cloyes True Double Roller timing chain
Comp Roller Tip Rockers
7/16 Hardened studs and guide plates
Manley Hardened Push Rods

I would go with forged pistons and would lower the compression ratio to about 9.0. The heavy load of your boat will make the engine more prone to detonation. Lowering the CR will help and forged pistons can handle the heat better. Also with a 9.5 CR, you would have to run at least 91 octane fuel. With 9.0, you can easily run 89 octane and probably 87 just fine.

These would get it done for you.

cams are mild enough for the long exhaust carry that you will have, and you can lower the comp a little and only loose a few HP's, but the torque numbers will still be up there.

These idle at around 500rpms in and out of gear all day long.

Thanks,

Learning a lot here. How would I go about lowering the CR down to 9.0? Should I be looking at the cam specs that jeff1000 posted on his dyno sheet? I do always run 89 octane.

Just order the piston that you need from JE for what it is that you are trying to do. Call Bob Madero for your cams. Make sure you are using large ovel chevy heads or mrelin ovals or something similar and a dual plane intake. Use a small bore carb to keep the velocity up and that will give you big torque numbers down low.

Run a EMI thunder or stainless marine manifold and then attach the long exhaust hose to that for the carry.

With that crank shaft you will make the power you want almost by defalt.

Do a custom roller cam from Bob RMbuilder, tell him what you want to do and what parts you already have. You will spend a little more money than with the flat tappet cam but well worth the expence.