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Bbc 454 gen 4 overhaul

Old 10-12-2020, 07:52 PM
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Default Bbc 454 gen 4 overhaul

Ok go ahead i have big shoulders i can take the abuse im new to the site. I am looking for help i just pulled my gen 4 ,454, 365 hp, bravo 1 setup out of my baja to rebuild myself and id like to bump up hp a lil just like every guy but I have never built a performance marine engine i have built numerous pickup motors and my mustang im a diesel mechanic by trade so I have the know how just need help with the parts list id be happy with 450hp roughly but I want it reliable it has 700hrs on it runs fine just think it's time lol any help would be awesome thank u for your time
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Old 10-13-2020, 12:26 AM
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The first thing you will need is good exhaust with longer risers.

Here is an OLD thread with good info. Paging Griff
To get to 450+ hp, use a Crane 168731 roller cam, Holley 800cfm #9022 carb and some mild port work on the heads.
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Old 10-13-2020, 04:36 AM
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So in other words I can buy any 454 rebuild kit and slap the extra suggested parts on it and meet my goals
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Old 10-13-2020, 04:51 AM
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Reason I'm asking i was told marine wise by a local engine shop that I have to bore .60 over to meet those goals i can just bolt an equation of parts together and get it with stock bore
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Old 10-13-2020, 06:28 AM
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I made 527hp/517tq on a stock bore 454.9.5-1 compr,flat tappet cam 230/236 ls110 .575" lift victor jr w/ a 930cfm carb.my sutphen ripped w/ that combo.eventually I ended up w/ a cam in the 250ish duration.
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Old 10-13-2020, 06:46 AM
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That is awesome I bet that is sweet ride I'm really glad to hear that I'm a newbie at the performance boating game but would love to do all the work my self instead of paying a shop out buying a motor
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Old 10-13-2020, 12:37 PM
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Boring .060 alone adds very little hp. Maybe 2%. You might need to bore it .030 to clean up the walls, but no reason to .060 unless its needed.
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Old 10-13-2020, 12:58 PM
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You bore it .060 and you're done. Anything else goes wrong your out a block or have pay to sleeve it. Not worth the meager performance gains. Boat motors are like any other high-performance engine, except TQ is about as important as HP, and more important for both is where they come in. Building something that make 600hp on the dyno at 7000 rpm is nearly useless in a boat. Think "how do I build as much HP as I can below 6000 rpm". I had two .030 over 454s, well massaged 049 iron heads, 9.2 compression, long tube headers and a Comp Cams "special grind" offshore cam, solid rollers, 780 cfm holley and dynoed 502hp at 5800 rpm (390 @ 6200! haha) and over 510 FT/lbs of TQ almost straight across the board. Worked good at cruise, had power out of the hole and could run top-end when needed. 450hp is doable on stock or .030 over bore.
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Old 10-13-2020, 01:18 PM
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Welcome to OSO. You have definitely come to the right place to ask questions. There's a lot of talented and experienced engine builders that hang out here. I don't claim to be one of them but I've picked up a lot of marine specific info over the years here.

My 29 Fountain has Gen-4 454 mags that were pumped up to ~500HP abt 7 years ago. Fortunately it was all done by the prev owner. Unfortunately I don't have all the specs. Having a mag eng is definitely a plus since they came with forged cranks and larger rod bolts too I believe (7/16"?). IMHO; the additional cubic inches from boring isn't much of a factor in the big picture. I would just have them take out enough to clean it up, If .030" makes the bore round again, I'd stop there. Make sure machine shop uses torque plates when boring.

A quality valve train is a must for extended high RPM operation. My valve train is all Crower and has performed flawlessly. Full roller is best but at least use full roller rockers. Stamped rockers flex and increase oil temp significantly. Exhaust valves take a beating compared to a car/truck eng so those will need to be high quality parts (S/S or inconel)..

Original oil cooler probably won't be able to keep up at WOT, so full throttle runs will be limited to a couple of mins or so until that is addressed. Definitely want an oil temp gauge if you don't already have one. A larger oil pan is a plus if you have the room.

Compression ring end-gap will need special attention since they tend to run hotter than you would see in your average car/truck.

Carb will need to be a marine version for sure. Mechanical fuel pump may or may not be up to the additional fuel flow demands, but that can be dealt with later.

Exhaust will need to be upgraded as prev mentioned to support the additional flow.

Compression ratio will determine what kind of fuel you need. If high octane is not available on the water where you run, that's something to consider. If running high compression, ign sys may need to be upgraded.

A rev limiter of some sort is highly advised since once the prop comes out of the water, there's virtually no load at all.

A wide band O2 (WBO2) is also highly recommended to dial in the mixture and ign timing. Keep that in mind when ordering/installing your new exhaust. Some manuf offer WBO2 bungs already installed in risers but may not be in the right place for your install.

Whenever possible, copy something that is proven to work well in the same/similar application. That will save you a lot of time and money in the long run. Good luck!!
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Old 10-13-2020, 06:25 PM
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I guess I have come to the right place you all have brought up awesome points and very helpful info I can't thank u enough now would u choose iron or aluminum heads like of I rebuilt my stock heads or bought new my plan was to buy everything to do a complete stock rebuild other than cam, switch to roller top end, carb and exhaust ? Any thoughts
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