Hi Guys!

My name is Massimo, i'm write from Italy, I always read this forum with passion.


I'm restoring a very old 454 mag carb for a Italian speed rib (Focchi 730 kevlar hull)


I have a dream to have at least 500 horses (the rib is very very light, @ empty 800kg about)

so far I have proceeded with these parts:


Speed pro piston +0.30 and +22cc dome (bored engine block )

Steel connecting rods H Beam

ALL bushings new by jegs performance (cranckshaft, connecting rods and camshaft)

And Alluminium Head with 115 cc (chambre) and 320 cc. square port.


i think i do 9.5 compression ratio.


other transformation that I want to do is the replacement a flat hydraulic lifter with hydraulic roller lifter and relative Camshaft.


My question for you is :


which camshaft is suitable for this configuration?

which carbs is the best for this configuration?


I apologize for my bad english and put pictures of boat and motor on it.

That's gonna be crazy with 500hp! I like it!

here's the cam specs that SB posted a while back that i copied. this is for the stock mercruiser 500hp carb motor:

For Gen VI HP500's cam I have the following in my notes:

Merc HP500 Carb
Crane Gen VI#169611 Grind#HR-284-2S-10IG
Adv 284, 292 at .004” Lift with 1.7 .576 / .598
At .050” 222, 230
ICL 105, ECL 115
LSA 110

Part Number: 169611 Grind Number: HR-284-2S-10 IG
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1996 Up CHEVROLET 8 HYD. ROLLER WITH CAST IRON DISTRIBUTOR DRIVE GEAR
Engine Size Configuration
454-502 C.I. V

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 339 @Valve 576 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 352 @Valve 598
Rocker Arm Ratio 1.70

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 33.0 BTDC 71.0 ABDC 284 °
Exhaust 77.0 BBDC 35.0 ATDC 292 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99896
Loads Closed 150 LBS @ 1.900 or 1 29/32
Open 441 LBS @ 1.330
Recommended RPM range with matching components
Minimum RPM 2500
Maximum RPM 6000
Valve Float 6500

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 6.0 BTDC 36.0 ABDC 105 222 °
Exhaust 50.0 BBDC 0.0 BTDC 115 230 °

Remarks:
CRANE 16535-16 LONG TRAVEL HYDRAULIC ROLLER- LIFTERS MUST BE USED WITH GREATER THAN .570 LIFT CAMSHAFTS TO PREVENT ALIGNMENT BAR DISENGAGEMENT.

Wally….That exact same HP500 motor, but with 454 msg short block was Mercruiser’s HP450. Yup, Merc offered it. Same carb, intake, heads, cam, exhaust….as the HP500.

really thanks for the reply!!

what pressure / flow should I configure with these components?

Use of mechanical pump?