Supercharging a 496...
 

I have a 2008 277 Islander with a 496 HO, wanting more power but I really don't want to change the motor. I would really like to go with a whipple charger but all i've heard is that a 496 cant be supercharged. There has to be someone that has had good luck with one. I know the 496 has cast internals but there are other engines that can be supercharged without forged guts. What has to be done to make it work?

The pros here say that the cast pistons will not hold up. Also cast crank will not like it much either. I hear there are a also fuel sytem mods and computer programing to be done. Sorry there is no such thing as cheap HP.

I know of two 496 stock boats with superchargers on my lake, and one 330 cast 454 with a roots style blowers as well.

All have stock cast internals. All have been running for the last 3 years with no problems.

The prob with a cast piston is just a little pre ignition knock (detonation) can blow the cast piston to pieces in seconds. Forged pistons will handle a lot more "knock" but no nock is good.

When you add boost, and some timing your chances of seeing knock are a lot higher, especially in a marine engine where fuel may easily get old, or have water in it.

Its a gamle, but speaking with one of the guys on our lake he states these rules-

Always fuels on shore, 93 octane
If fuel sits for longer than 3 weeks he adds 110 race fuel to mix with 93
Changes fuel filter twice a year
Inspects fuel system and igniton twice a year
No wide open runs for more than 5 mins

I don;t know who did any of the programing or other changes, and i won't see these guys til May again.

no wide open runs for more than 5min? oh there goes all the fun, i run wide open for 20-30min all the time

No one wants to change an engine until they realize that boosting that particular engine was a mistake. If you really baby it and don't run it very hard, it will live for a while but at that point you may as well leave it alone and run it hard.

Sure, there are people that will tell you it's okay. This has been debated so many times... Looking for "one" (someone) to tell you that they had no problems?? Wouldn't you rather find several owners that all agree that spending that type of money won't send you in the "other" direction??

It really doesn't matter that there are "other" engines out there with cast internals that also have forced induction.

You're asking about the 496. If setup properly, it's great, closed cooled package allowing you to keep all of your accessory drive components etc..

If you don't want to build it to last (spend money on what you currently have), then by far the best way to handle your desire for more power would be to sell your entire engine as a take out and start over.

You can spend a lot doing it correctly. Or you can spend even more dealing with it after you went cheap (or cheaper).

I did mine and had great time with it. With that been said it is still not for everyone. PM me your number and I talk to you about my experince with it.

So would upgrading to forged internals and a boost friendly cam be a cost efficient option to a motor swap? Is there any other weak points in the motor to be addressed?

I think there are some fuel system mods and computer upgrades that should be done. The Miami boat show is coming up, some of the pro's must be really buisy right now. I'm sure they can give you more details.

Then of course there is still my favorite idea-

Take your engine out, and put it in the corner

Buy a high performance engine that will drop in, if used get it freshened first.

When you are done put the stock back in your boat, it will sell faster and most like be worth more than it would be with aftermarket mods to the stock engine.

Bonus- you have the high perf engine left to sell outright or use in your next project

Very well said +1

Whipple makes a complete kit that will bolt on. It includes everything you need plus reprogramming of the PCM. With that said, no one can tell you how long the pistons will hold up. They are the weak link. The 496 pistons are weaker than cast 454 pistons. The reason being is they were designed with a very high top ring land to help with emissions(as I understand it). That leaves them weak when subjected to higher than normal loads. I just rebuilt 2 Whipplecharged 496's, upgrading them to forged internals. My recommendation would be to upgrade the pistons and then add the whipple. Tyler Crockett sells some forged factory replacement pistons made by Diamond. Use them and keep the rpm below 5400 and it should live ok. The engines I just rebuilt had been running for 2 years before a piston failed. They had maybe 60-70 hrs on them.

Bob Lloyd
Full Throttle Marine

The problem is not with the internals it is with the setup of the internal for n/a. Yes the top ring is set high on the hyper pistons. For these to work in a blower app you must open the compression ring end gaps a lot. If you don't they will butt and it will lift the ring land. This of course is not a piston failure but a setup failure. Beyond ring gaps, you need better head gaskets, head studs, better fuel management to ensure rich a/f and less timing. What would stop me from supercharging a 496ho is the ring end gaps and computer. Put on a carb/tbolt ignition and open the ring gaps and a few other odds and ends and it will run great for as long as a forged assembly.

Blower motors
 

You can ask around until you find someone to tell you they have put a blower on a 496 and it hasn't blow up-yet. But that will not stop it from coming apart. I have been running superchargers on boats since the mid 80's and have blown up a few engines and melted a few pistons along the way. You should see the wall of broken parts I have accumulated over the years and the one thing I can guarantee is, the better the parts you start with, the longer and more trouble free your project will be. Blowers are not magic, they just increase the volumetric efficiency of a motor and make it burn more gas, thus make more hp by forcing more air/fuel mixture in a cylinder before the spark plug lights it off. If you want to put a blower on a stock motor and turn the boost way down and not run it hard, it will last a little while. But if you spend the money on a supercharger to go fast and then you baby it, you are a better man than I. I have extreme motors and boats because I like to run the crap out of them. If you don't, why have a blower? For looks? I know it seems easy and cheap to just bolt a Whipple on your engine, but most likely you will not be happy with the results. You can sell your 496 for 6K to 8K if it is in good shape and put a 454 in there with good parts, (not top of the line but good) that will be a much more dependable motor that you can actually use normally and make 650hp.

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One of the first boats I supercharged

Whenever anyone asks about mod-ing a stock engine, this disclaimer should automatically pop up. This is the best advice you can give someone asking this question. Period.
Eddie