New BBC build, looking for advice.. anyone out there?

[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 (which will fit under the engine cover without cutting the sundeck) 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?

[iadr]

I don't think anyone is going to have anything nice to say about the Pro-Comp heads. Particularly as some of those being ripped off are active members of this board.
Flow bench figures aren't the whole story, particularly if you compare a maxed out 2nd quality head vs. a premium head as cast.

With that said, it that it sounds like you are fairly well informed on the general choices/compromises of part-selection.

Not sure where you are heading with the comparisions of superchargers- bigger will run cooler, but really the choice is yours- different potential, different levels of mods to the boat, different price levels.
Anyway, I am going on a bit without specific to offer.

I would say you need to give more details about how you use the boat and how the drive is set up- what RPM is it going to pull at full throttle?

[Ed-vancedEngines]

Simply put, no matter if you have one of the better quality ones or what the flow is. That head casting is too thin to put a blower on.

Ed

[cboggs]

Yep, .. that head is now where near good enough for any engine
making power, much less a blow motor.

C

[Cisco398]

I have had alot of conflicting info about the Pro Comp heads. Some very good, some not. I may have to rethink them. Would the best choice be Dart, Merlin or AFR? Anyone have experience with either of them? Would either of these heads require me to rethink the cam? I know its alopt of broad questions... but I am hoping to learn a few things before I had the engine together. Also I was looking into an intercooler but for the price maybe I should opt for an 8-71 or even a 10-71. I was hoping to keep the carbs under the engine hatch and sunpad. Anyone know where I can get some "Do not sit here" stickers?

[MileHighMan]

Cisco, I got an excellent deal on my Dart pro-1 heads from a guy in Wisconsin. p/m me if you want more info. Also your local sign maker can probably handle your decal needs, since alot of the signs produced today are just decals stuck to plastic board. Good Luck on your engine build. Ed, your a wealth of information. I never thought about the pro-comp heads being too thin to set a blower on. Learn something new everyday. Thanks. Dan.

[J C]

Do you have a closed cooling system in the boat? If not you might consider the water where you usually run. Some water can be rough on aluminum.

Sure would hate to eat up a set of nice aluminum heads from the inside!

J

[Ted Gerstenslager]

Stay away from using a boost retard in a marine application . As it functions it will send exhaust temps higher. Inconel or equiv. exhaust valves suggested for blown applications. If it stays retarded for any length of time you will melt some stuff. Intercooler over 5.5 ps no more than 28 degrees of total. Best use a detonation sensor setup from livorsi marine.

[cboggs]

I have had alot of conflicting info about the Pro Comp heads. Some very good, some not. I may have to rethink them. Would the best choice be Dart, Merlin or AFR?

I don't know a nice way to say it, .. so, .. the pro comp stuff is junk, ..
I don't even let it into my shop, .. crack, seats fall out, machine work
really poor, ..

That being said, we use the Dart race series heads for blown applications.
Like the Dart 320, 360 etc, . they are thicker & stronger then
the Dart Pro 1 line of heads, ..

you might also look at Edelbrock Victor, nice strong casting, or a Brodix\also strong castings, ..

Curtis

[Cisco398]

I was able to get different heads for my build. 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? Also I would like to get max HP at 6000 RPM, any suggestions on that?
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

AFR 305cc Aluminum Cylinder Heads for Big Block Chevy
305cc Intake Runners
119cc Combustion Chambers
Premium quality stainless steel valves - 2.250" Intake/1.880" Exhaust
Heads feature a stout .750" deck thickness
New Comp Cams Beehive springs (PN 26120) and titanium retainers (PN 788)

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?