cisco398

This is the first project I am attempting for use in my boat. What I am looking for is feedback on this project. Estimated HP and CR and suggested boost. Any pointers on the best combo for reliability and performance. (I know, some say bigger is better, but it’s not always true ) but since this is going into my boat there aren’t too many gas stations between buoys. What are the pro’s and con’s between the 177 with a single carb vs. the 6-71 with dual carbs? Will the 177 with a 850 be a better choice over the 6-71 with the 650’s?

I started with my 1991 Bravo Mag. 454 4 bolt main block going .030 over for a 489 (maybe .060 for a 496... decisions, decisions!!!). The casting number is 10069286

PARTS 489/496 FORGED ROTATING ASSEMBLY
FORGED STEEL NITRIDED CRANKSHAFT STROKER 4.250"
4340 H-BEAM ROD SET BBC 6.385
KB PREM FORGED PISTON BBC 489 3CC FLAT
AKERLY & CHILDS EXTREME PISTON RING SET 1/16 1/16
3/16 4.310
CLEVITE PERF ROD BEARING, NEW MAIN BEARING SET
Melling M77HV BBC Oil Pump

COMP Cams #2110Big Block Chevy Magnum Timing Set
COMP CAMS XEM 234-244 @ .050 110LC 1 165.00 165.00T
HYD LIFTER SET

PRO-COMP ALUMINUM CYLINDER HEADS
320CC INTAKE RUNNERS, 115CC COMBUSTION CHAMBERS, 2.25 INTAKES
AND 1.880 EXHAUST STAINLESS SWIRL POLISHED VALVES. 1.460 DUAL
VALVE SPRING ASSEMBLY. 1.460" Dual Spring Assembly. Suitable for Mechanical Flat Tappet or Hydraulic Roller Cams up to .650 Lift 140 PSI Closed / 360 PSI @ .500 lift. .400 THICK DECK.

FLOW DATA @ 28" H20
PC3021 .100 .200 .300 .400 .500 .600
INTAKE 74 166 245 308 340 360
EXHAUST 62 118 160 195 229 248

I have a choice of superchargers and carbs. Weiand 177 or 6-71 BDS/GMC BLOWER BIG BLOCK CHEVY with either combination of 2-850 CFM Holley, 2-650 CFM Holley, 1-750 CFM Holley.

I am also planning on the MSD Boost timing master with rev limiter. Anyone use this before that can advise?

Griff

The Weiand 177 will work, but will not make close to the power of the 671. You will have to spin the 177 way too fast to pump enough air into 496. If you have either as an option, definately go with the 671.

RaggedEdge

cisco 398

Depending on what you want in terms of horsepower you might look into building based on Mercs 525SC. These were based on your 454 Mag, using a lower comp piston and the stock rect port heads. Heads were set up with 2.25 stainless intakes and 1.88 Inconel exhaust valves. Cams were flat tappet hyd from Crane along with their springs and Gold rockers. A Weiand 177 at 5 lbs of boost with a 1050 Dominator. A simple and conservative engine combo that has a super reputation for reliability. Any Merc dealer should be able to provide all the specs for this engine out of the HP manual.

I ran a pair of these for years with nothing but plugs and oil changes yearly. If 500-525 hp is not enough you can add a Superchiller with their upgrade blower pulley to up the boost to 7-7.5 lbs and end up around 600 hp, and still have a reliable combo. Mine were intercooled with the higher boost and I loved these engines for six seasons, they are still going strong now, three seasons later.

KAAMA

iTrader: (1)

Call RMBuilder/Bob Madara of Marine Kinetics in N.Y. and run it past him. He can answer your questions and provide the right cam and valve train components for you as well as counsel you on your application. Have Fun. Bob's number 585-654-8583