Reply With Quoteboth the blowers seem a little small for a 496, but if you gotta use on of them, i would go with the 6-71.
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 its not always true ) but since this is going into my boat there arent too many gas stations between buoys. What are the pros and cons 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 650s?
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?
both the blowers seem a little small for a 496, but if you gotta use on of them, i would go with the 6-71.
I see you don't have PM's set up yet.
I agree that the larger blower is better for a 489/496. I would probably stick with the smaller bore if the block cleans up, to give you one additional bore in the event that the engine needs to be rebuilt, either due to usage or damage. 7 cubic inches is not going to make that much difference in power.
I have a few other ideas and suggestions, feel free to email me direct at obnoxious001@yahoo.com
I do understand about the latger blower, but I was hoping not to cut the engine cover and sunpad. Are there suggestions that can make the 177 work? If not I may have to cut the engine hatch. I just had it recovered this spring.
Just build a N/A motor with the same HP and save on the weight.
I don't think they're made anymore, but B&M had a low profile 250 that I think would work well if you don't want a sunroof in your engine hatch. I'm pretty sure they're the same or close tothe same height as the 177, just longer. You'd have to find one used though.
The 177 is a single carb deal. It also spins about triple the rpm's of the 671 to get the same amount of boost. The 671 uses a cog belt instead the the serpentine of the 177 which can slip. I think you would have a hard time getting any more then about 5 lbs. boost from the 177. Holley now owns B&M and the B&M was the 177. The weiand is a 174 I believe.
Don from TPMarine (Arizona) just put up a nice 8-71 and carb combo for sale.
Click: http://www.speedwake.com/upload/show...threadid=52429
BTW: He's a great guy also. Have purchased a good amt of things from him.
Rethink the oil pump......Unless you are going to do extensive re working inside. Look in to the mellings 10777, 10778, or 10778C pumps. They are double in price, but there is a reason for that.....Quality..........MP
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?
what are the issues with the Melling?
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