The flame arrestor on some apps rest right up against the back of the bench seat restricting air flow into the engine. Sometimes they are impossible to get off because of this.

Also you are 100 % correct a dirty flame arrestor will hurt performance. The 496 Flame Arrestor might look clean from the outside but went you take it off and clean them from the inside out you will be surprise how much crap cleans out. (belt dust, carpet fibers, gas/oil deposits and so on.

Your engine will run a lot a better from a flame arrestor that is totally clean and can get as much fresh air as possible. Look into it might surprise you how your motor will run afterwards.

I have done the upgrade on several twin engine boats with great results..

KA the valve,springs,rods,crank are all the same on 496 Mags and HOs,,the issues you have with yout pistons and rods are not from the cam upgrade,

Nothing but cast in the 496. And believe me I know about hand grenade Pistons and some bent rods in the 496. The first year they freakin come out - push rod / engine failure for certain serial # runs.. Then a Service Bulletin came out and letters went out to those owners stating your motor needs the push rods changed PRONTO or engine failure can occur.

I always turned down the pro charger / super charger jobs when the 496 was involve as I did not want the liability nor the headache nor being married to the owner of his boat and his engine. Now did I sell them to the owner - Yep and that was it - there boat they are going to do what they want with it anyways.

KA what hand cleaner did you use to clean up that mess. looks like a land mine hit.

No, it was from running the boat at 5150 from Boynton to West Palm, ingested valve, see pictures. I think its crazy to swap a cam and reuse springs. Especially springs that are that weak. Keep in mind the OP has a single engine Baja. It takes 15-18 HP per 1 MPH in a twin Baja. I am guessing every bit of 20 HP for 1 MPH in a single engine Baja. So is it worth 2 maybe 3 MPH?

5 years ago I was the biggest fan of 496 and I still am, I have twin 496/8.1 based 600's, that I built and I love them. But if you dicker with them they will bite you back. I just cant warrant changing a cam for 2 MPH. After 5 teardowns of stock 496's, the two things that always perplexed me were the springs and the pistons. They just dont fit in a marine scenario. The thing is you can upgrade the pistons for only $700 and never worry again and then go crazy with heads, exhaust and the like and get decent power out of them.

LOL the funniest part was taking the heads off in the boat and looking at all the cylinders. The valve tulip was gone on the last cylinder combustion chamber. Since the damage was in the back and I was working on my stomach I was reaching in each cylinder blind and assuming I would find parts. I reached in the back cylinder and my arm went down nearly to the crank and my hand hit the wrist pin. It didnt compute, I was like is that the valve.... wait a minute... its the freaking wrist pin. OK folks... we arent fixing this one with a 12 pack and duct tape, the season is over.

I know every motor hates to run lean but the 496 really hates to run lean and seen pistons come apart as well. Stock 496 seems to flat out around 80% to 85 % of throttle. IMO they have good low end and somewhat good mid range but the top end is just not there.

Your story is bad for you and funds but the way you tell it is funny. Do not jinx it for the future.

Some of the very early HO's supposedly had a forged (Kellogg?) crank.

Mercruiser advertised it but I think when they finally got the black production 496's rolling out to the boat builders that changed.

I know this for a fact 100% that Volvo penta from day one did not have a forged crankshaft and they along with Merc bought from the exact same GM source but marinized them differently. They both still used the same crank among a lot of other parts.

I took the first OEM class from Volvo Penta as soon it came out back in 2000 or 2001 all about their 496 / 8.1.

I still have the class material & booklet stored away and that info was in there about the crank as well. I will try to dig it out and report what it says. I remember pics that Volvo posted "this is what we buy and this is how we marinize it" with before and after pics. Anyways FWIW.

The 496/8.1 catches a lot of crap but its a pretty sound design. Its basically an LS big block once you run the Raylar style heads. The Raylar heads are actually really nice stuff, Darrin Morgan really did a good job on the design. I am not a big fan of the DART heads and I have seen them in 2 separate applications and they are well suited if its a blown application built for being supercharged. If I could go back and built mine with DART 496/8.1 blocks with 4.5 bores, it could have been an awesome project. The shortcomings that I felt were weak were the pistons, springs and the fact they came with traditional rockers and not roller rockers kinda sucked. Later I learned more about the blocks and they are okay for a marine application but they are actually a little weak. I have heard 4 separate stories about the mounts ripping out of the blocks from the castings being thin... I mean they were meant to be truck blocks anyway, but it always scared me in rough water conditions. They are different but they are fun, they are kinda like the 409 of early years, the bastard stepchild.