Would like to make 600hp out of a HP500

[axapowell]

Need some help from anyone who has already done this (I don't want to re-invent the wheel).

I have 2 1999 HP500's, carbed, and want to upgrade to 600 horsepower. I wound rather not go to blowers and am hoping to just upgrade the heads and cam. Anything more then about 620hp will require a drive upgrade, so I'm not interested in going any higher.

I have the Merc HP exhaust manifolds and Gil risers, so I would assume that exhaust is not an issue.

Dart intake and 800cfm (or 850) Holley's. Plenty of CFM and flow on the intake as well to handle the additional horsepower.

I have access to a dyno and will check the hp and torque curve on the current setup and build from there. Someone has to have already done this. If I have to, I will upgade the distributor and change the factor rev limiter so I can pull a few more rpm's but top out at around 5800.

I want to continue to run pump gas (89 octane) and keep the reliability factor. Does this sound doable? Thanks in advance for the help.

Dave

[t500hps]

"excursion" did this to his carbed 500 this past winter. Ended up close to 600hp. He can give you more info.

[cobra marty]

Send your steel heads to JimV or use alumn AFR315cc and Crane 731 cam will get you real close.

[800XCR]

Your exhaust is an issue....guaranteed.

[cstraub]

HP is a calculated number based on torque x RPM. RPM is not a friend of I/O boats. I would keep your top half and buy cranks rods and pistons and build a set of 540's. Nothing like an extra .250" worth of arm to ad gobs of torque to an engine. The 188 heads you have are fine for 540 inches.

[Boatally Insane]

I built up a 509 this past spring for my boat...

On the dyno run I posted it made 595 hp at 5400 rpm

On another pull it made 599.5 hp at 5600 rpm...

This is with "dyno" headers turning the water circulating pump...

For exhaust I ended up using Keith Eickert's but I don't think reversion would be an issue with what you have...

It has run GREAT all summer long...


502 mag build

502 block bored .030 over to 4.5"
JE pistons, wrist pins, and rings.

Stock crank turned .10 .10
stock connecting rods resized with ARP bolts.
Balanced Rotating assembly

088 casting GM iron heads custom ported at NVR racing
with Manley 2.25 stainless intake and 1.9 inconel exhaust valves.
118 cc chambers
8.9:1 compression
ARP head bolts.
Gasket Specialties head gaskets

Custom Ground Cam Motion cam (spec'd by rmbuilder)
Intake .594 lift 228 degrees duration at .050
Exhaust .600 lift 232.7 degrees duration at .050
112.2 degrees lobe separation
Morel hydraulic roller lifters
Crane gold roller rockers

Edelbrock Victor Jr intake port matched to heads
Demon Mighty Marine 850 carb with #80 primary and #88 secondary jets. The only adjustment required on the carb AT ALL was idle speed!!! The jetting was right on the money!!

Modified Mercruiser magnetic trigger distributor
Crane Ignition box using their #6 advance curve with 14 degrees initial timing advancing to 34 degrees by 2500 RPM
Autolite AR135 spark plugs
Mercruiser plug wires .


Doug

[Back4More]

Cam, and heads with 9.8 to 10:1 CR...55-5600rpm
Dart Pro1 alum heads if your going to keep those Gils, and for more power a set of the Pro1 CNC'd and some CMI's
Isky Hyd. roller cam...ground @114CL
http://www.iskycams.com/engine_templ...7&engine_id=20
Grind No.
RR-284/294 HYDRAULIC ROLLER

[cstraub]

Bill,
Kip, Cam Motion, does not give out std cam cards. Cam Motion runs Cam Doctor on each cam which prints out the exact spec's at which the cam is ground.

Chris

[axapowell]

I built up a 509 this past spring for my boat...

On the dyno run I posted it made 595 hp at 5400 rpm

On another pull it made 599.5 hp at 5600 rpm...

This is with "dyno" headers turning the water circulating pump...

For exhaust I ended up using Keith Eickert's but I don't think reversion would be an issue with what you have...

It has run GREAT all summer long...


Doug

Ok...Alot to process. Sounds like a great combo, but don't I already have most of that in my HP500?

Victor Jr= Dart intake+porting
Demon 850 cfm Carb= Holley 850

Crane cam in HP500 Intake .576 lift 222 degrees duration at .050
Exhaust .598 lift 230degrees duration at .050
110 center
Your grind: Intake .594 lift 228 degrees duration at .050
Exhaust .600 lift 232.7 degrees duration at .050
112.2 center

JE pistons, 118 cc chamber, 2.10 intake valves, 1.88 exhaust, crane gold roller rockers.

So, if I got this right, I can go to a GM Signature Series Rect. Port Aluminum head (GM PN#12363400) with the bigger intake valve (2.25/1.88E) change the exhaust valves to Manley Inconel and a bigger cam similar to yours, keep the stock bore(if I can) port my intake manifold to match the gasket and heads, change the module in the distributor and add a rev limiter with a box(MSD or such) that should do it? A few less cubes, all good bottom end, and balance the rotating assembly...This should be around 600 hp at 5600-5800 rpms.

Hmmmm....has anyone else had a winning combo?

Thanks so far for the responses!! BIG HELP

Dave

[axapowell]

Here is the specs on the heads:

12363400
Signature Series Rectangular Port Aluminum
Cylinder Head Assembly
Rectangular port head made from 356-T6 aluminum alloy for
1965-2000 Mark IV and Gen V & VI 396, 427, 454, and 502 bigblock
engines with compression ratios below 12.5:1. High
velocity 315-cc long intake runners and 300-cc short runners
enhance mid-range torque and throttle response. Exhaust
runner volume is 110 cc. Semi-open 118-cc combustion
chamber design provides very streetable compression ratios.
Rocker studs and exhaust bolt holes are heli-coiled for
strength. The 9/16-inch deck surface provides maximum
strength and greater head gasket sealing. Intake and exhaust
ports are in stock locations. Head assembly includes 2.25-
inch stainless steel intake valves P/N 12366987, 1.88-inch
stainless exhaust valves P/N 12366988, 1.55-inch valve
springs P/N 12462970, valve spring retainers P/N 12366990,
valve spring shims P/N 3875916, valve locks P/N 12366992,
and oil seals P/N 12495690. The above part numbers can be
used for service replacement parts. Heads require cylinder
bolt kit P/N 12367779.