Building 496 stroker

[fastestonehere]

OK! i not sure if i fell off the deep end.. my boat is a "88" Trojan 10 meter. this boat ran ok this year 33 mph on gps witch feels great in this size boat. i need to rebuild the motors so i feel like doing a stroked 454. now i thought i would get some info from others here. anybody do anything like this to a cruiser. this thing is around 16,000 pounds

also i have built many motors and now the importance of great machining.
the plans are

496 stroke kit all forged internals 9.5-1 comp. heads are 308cc intake runner with a 119cc combustion chamber, a 2.250 intake valve and a 1.880 exhaust valve , performer RPM air gap duel plan intake manifold, and a 950cfm carb or dominator, Hyd.Roller, Revolution marine exhaust manifolds.... now i have left the cam open? this is where i need some help. i want it to be reliable not building it on the edge but i feel that 575-600 HP should be doable. my drives are velvet drives not v-drives. also i know that the reverse rotation motors crank needs to be cross drilled and reverse polised any other information would be great.

Thanks i hope i did not hit any nerves with anybody on here.

 

[1fishbone]

Re: Building 496 stroker

Choosing the 'right' cam for a boat is different than for a car.
Where you are buying the kit would be a good place to ask about a cam.

Don't forget making a changing the electronics or distributor.

Are you using the Gen 4 block?

 

[paw2000]

Re: Building 496 stroker

Hi, I had built a 383 motor and machining is key to longevity. I had a custom ground camshaft made by Shannons Engineering in Minnesota. They took my application, rpms and what I needed and custom ground a cam to match. Cost was about $185 for a roller cam. My application was a fuel injected and I needed good vacuum as not to throw the computer off.

What gear reduction velvet drives you have now? if you top out at 33mph what was the rpm? build the motors for lower rpm torque and re-prop as necessary. Here is a link to velvet drive ratings.http://www.velvetdrive.com/techinfo/V7172/V7172pg3.pdf

Group A shows about 5000 rpm max and 500hp, build the motor for that and it will last a long time . This link explains the classifications
http://www.velvetdrive.com/techinfo/V7172/V7172pg2.pdf

 

[Lyle29464]

Re: Building 496 stroker

The weak link in you plan is the cam.
You really need advice from a person that has done several projects like yours.

Most all BW transmissions are made with a reversible front pump. This can be done in minutes.
While you can not change the output you can use a left or a right engine.
The props would still turn outward and offet most of the torque but you still would have some torque from the standard turn engines.

Finding a reverse turn cam or having one made by a shop that really knows reversion http://www.michel-christen.com/ExhaustElbows.pdf is the challenge. make sure the person your talking to has built a "wet" system. Any cam will work in a dry exhaust.

 

[zbnutcase]

Re: Building 496 stroker

Best bet is to call the cam makers directly and discuss your project with them...Comp Cams has a good support line...

 

[proshadetree]

Re: Building 496 stroker

Have you noticed your tach jump right up in you boat when you push on the throttle? Your boat then catches up with you engine. It takes a lot of improvement to notice much in a boat.If you old engine redlinned at 5000 rpm and you don't build your new one to match a higher rev limit then longevity will be sacrificed. I have witnessed many people build high rpm screamers that are not very good for general use and are depressed by how they did not make their boat a racing machine. An automobile will show drastic improvements compared to a boat. Until you overpower your drive train or tires. Actually fast boats have many more things going on that engine improvements. Matching the prop with the drive with the engine to the hull design is critical to ensure optimum performance. I do not want to dissuade you from you project just be the voice of reason. Hope you post progress pics if you desire to go through with it.

 

[dockwrecker]

Re: Building 496 stroker

Carb sounds too big to me. I'm thinking a 750-800 cfm would flow better at boat RPM's.

 

[fastestonehere]

Re: Building 496 stroker

Thank you for all of your reply's. I am going to listen to my cam builders sigestions just thought i would see if you guys had any info.

also thank's on the velvet drive ratio link that will be helpful.
I will be re-proping the boat I forgot to mension that I will have the prop built
around the 5k rpm range with the horsepower and torque values at 5k.

what boat cam makers are out there and good prop companys

any help appricated.

The boat was proped a little to big by old owner it would only max rpm at 3800 and it was slow getting to there. i could roll up the throttle easy to 34-3600 rpm but a fight past there.19x20 4 blade nib. boat stock i think was a 18x18 or 18x19 3 blade.

 

[paw2000]

Re: Building 496 stroker

If you go custom ground, any company can make them, I used Crower for my old chrysler big block as the cam actually turned backwards and had special cut gear for oil pump and dizzy. Shannons I used for my chevy 383. All chevys camshafts turn clockwise from the front so that makes it easy to match cams.

Since you are building a big block that should flow well, consider doing the 4 7 cam swap (firing order change to improve flow), this will improve flow and give that cool exhaust sound. The cam company can make matching cams. You have a fun project ahead.