HOTTZU98

Do the 496"s have forged crankshafts and rods like the old 502MAGS? Someone told me they are not forged but cast is this true? Thanks for info.

Hydrocruiser

Specs for the 375 HP (same internals as the 425)


-496 cid
-Comp ratio 9.1:1
-2 valves/cylinder
-4 bolt (cast iron) main bearing caps
-Internal balanced
-734 lbs
-375 Hp at 4600 rpm
-490 lb-ft at 3200 rpm
-Cast iron block
-Cast iron head fastened with 18 bolts
-Crank.. cast iron-nodular
-Aluminum intake
-Hydraulic/roller lifters
-Camshaft..steel
-Rods..forged steel
-Pistons..cast aluminum

My take...in examining the power curve it appears that the torque comes on fast and then drops off rather fast as well. If you like hovering around the 3200-3500 rpm range you are fine....this is more what one might expect to see designed for a cruiser and not an offshore boat.

Good points:
-Very solid and well mounted iron heads
-Aluminum intake
-Nodular iron crank is the next best thing to forged and can handle 500HP.
-Good cam and lifter set up


Not so good points:
-Heavy iron heads; not all that great flowing
-Intake manifold not designed for offshore use
-Powerband is too narrow
-Compression is low
-Pistons are perhaps the weakest design point and the hardest to change overall.
-Exhaust system is not HP


"Editorial"...
I have read where the coating on the pistons makes them brittle and spark detonation will destroy them quickly. Supercharging may get you the HP but not overall durability.

The powerband is all wrong.. especially on the 375 HP... for offshore use. They need a new cam first and foremost...then..performance aluminum heads...performance intake manifold...performance headers...ECM recal...to make 500 HP.

A fun project if you like doing this kind of stuff.

Raylar

Some of the 2001 496HO's actually had forged crankshafts, until GM developed a cast crank that was cheaper to make and just about as strong. We bought up the remaining inventory of GM 496 forged crankshafts and we use them to build our HO600 engines.

Ray @ Raylar

FOUNTAINATLAST

Is there a way you can tell if your 2001 496 has the forged crank???

Hydrocruiser

..


The change was made in late 2001 supposedly...so if you have a 2001 496 it's a good chance you do have a forged crank...but too bad the pistons are not as well...

The 496 is a nice platform it just has a crappy cam more adept to a cruiser's needs...crappy heads...crappy exhaust and an aluminum intake to support low to midrange power bands....otherwise it is pretty decent...

...considering you will pay about $14,000 in addition to the price of a 496 HO to get a 525 HP ....if you are handy this engine has potential for 500 reliable HP. Just avoid spark knock at all costs...modified or unmodified...the pistons don't like premature detonation at all.

Cam/intake system/heads about $5,500.00 from Ray....then headers...so about 8 grand/engine to get up to say 550 HP....
about 6 grand less per engine than if you went with an HP 525 to begin with. Roughly. If you do it yourself....labor and or warranty concerns will obviously push in the direction of getting the 525 .

...now Whipple says up to 50% increase in HP with 5.5lbs of boost. They run about 7 grand.

Either way you still come out cheaper than a 525HP. Expect both mods to crank up your engines octane requirements...spark knock will kill those pistons..

Personally if they were my engine(s) I would put on Raylar's heads and a header exhaust system and then add a Whipple. With 4-5 psi I would bet you would be seeing
650 HP and with that amount of boost not loose reliability.
with that set-up. That would cost about15k/engine if you did it yourself. Not cheap but we are talking 650 HP now! What's 600 Mercury ponies cost these days?

FOUNTAINATLAST

After spending about 15K to get that horsepower with the possible lose of reliabilty, I would rather find a 525 and drop it in the boat. Yea maybe less HP but truely reliable, then ditch the 496 for maybe 5-6K and would have only spent 3-5K more then buliding the 496 in the first place...??? Unfortunatly I didn't buy the boat new otherwise I would have probably gone with an 500hp at the time...

Raylar

The stock 496 with our kits is very reliable, just ask the 75 or so boaters all over the world who are running them. As for 15K, where did you come up with that number. Add a Raylar BCK103 525HP kit for 8K including professional install and you have a motor that will run with a HP525 all day for about 14K less. Add 3K to 4K for good headers and the HP525 will read your transom all day. Upgrade your 496 to our HO600 and the HP525 won't even be able to find you.
Good Luck with ditching the 496

Ray @ Raylar

FOUNTAINATLAST

The 15K is a round figure Hydro came up with when he mentioned adding your kit with a Whipple. My concern with adding mods to the 496 is not the dependabilty of your kit just the fear of the weak pistons... I could spend 8K for your kit get detenation ruining the piston now need to rebuild the motor and spend more money on an inferior 496 motor. Ditching the 496 would probably be the easy part, I already have people wanting to upgrade from there 454 if I chose another motor route.

Hydrocruiser

http://www.chevyhiperformance.com/te...8/index15.html

This performance shop will build you a 496 HP/550 lb ft torque 496ci crate engine....
for $5,550.

With all the good parts..

If they can do it so can "big M"