454mag top end rebuild
10-14-2013 | 11:03 PM
#23
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Joined: Jul 2004
Posts: 11,332
Likes: 73
From: chicago
Lets try to get back on track here. Turned into a which head is best, who knows engines and who doesn't, etc.
Lets talk about the 454 Mag for a minute. Its weak points are
Flat tappet sissy cams
GM 1960's castings for heads. They can work depending on your goals, but any good aftermarket head would be a improvement.
Exhaust Manifolds. They suck if trying to make anything over 375-400HP.
Intake Manifolds. They are decent, the old days cutting down the center divider and adding a 1" spacer helped them out.
Quadrajet carb. Great carb, but if serious about power, they can be limited, and tuning can be a little tougher than a holley.
Rocker arms. Stamped steel style.
Some of the strong points are
4 bolt mains
Forged Cranks
7/16 Dimple rods
Forged pistons
Now, I know your not at sea level, so that will change things. But, generally speaking, to get a Scarab III to run mid to upper 60's, is gonna take around 500HP per side. Mid to upper 70's, around 600HP per Side. In the 80's, 650-700HP per side. Once you establish what you'd be happy with as far as speed/power, then maybe we can start spending your money. If you'd be happy with 75-100HP increase per engine, there's really no reason to go spending 10k dollars worth of fancy aluminum heads, exhaust, roller cams, and other goodies.
The 365HP mags respond well to a cam swap, exhaust upgrade, roller rockers, intake and carb. The old 420HP, 440HP, and 460HP 454 based mercury engines used basically a 365HP bottom end and heads. They got better exhaust, better valvetrains, intakes and carbs. If your gonna be using the 496 exhaust manifolds, I'd be careful with cam choice, from a reversion standpoint. They are a improvement over the old iron manifolds, but they aren't long riser'ed dry pipes.
In my opinion, what makes someone a good engine builder, is knowing combinations, and what each combination will produce. To be able to meet a customers budget, and most importantly, deliver a reliable product. HP doesn't mean squat if it doesn't stay together. In todays world, you can almost make 600HP from a big block chevy by accident. Making a 600HP marine engine that lives takes a little knowledge. I'm not gonna keep going back and forth on the whole oval vs rect port thing. I posted up a video of a buddy's old scarab III's setup, and Borgie seems to question the choice of parts used. Could he have made more power with different parts, surely. In that 10k lb scarab, 20HP doesn't mean $hit. He liked the look of the single plane intake, so we went with them. he could care less if the boat goes 65 or 65.8mph. But I can tell you this, that kid runs the ****T out of that boat every single weekend. Theres no cruising, its WFO everywhere he goes. Theres no issues whatsoever with the engines. A blown TRS, sure. But the engines run great, 89 octane.
Lets talk about the 454 Mag for a minute. Its weak points are
Flat tappet sissy cams
GM 1960's castings for heads. They can work depending on your goals, but any good aftermarket head would be a improvement.
Exhaust Manifolds. They suck if trying to make anything over 375-400HP.
Intake Manifolds. They are decent, the old days cutting down the center divider and adding a 1" spacer helped them out.
Quadrajet carb. Great carb, but if serious about power, they can be limited, and tuning can be a little tougher than a holley.
Rocker arms. Stamped steel style.
Some of the strong points are
4 bolt mains
Forged Cranks
7/16 Dimple rods
Forged pistons
Now, I know your not at sea level, so that will change things. But, generally speaking, to get a Scarab III to run mid to upper 60's, is gonna take around 500HP per side. Mid to upper 70's, around 600HP per Side. In the 80's, 650-700HP per side. Once you establish what you'd be happy with as far as speed/power, then maybe we can start spending your money. If you'd be happy with 75-100HP increase per engine, there's really no reason to go spending 10k dollars worth of fancy aluminum heads, exhaust, roller cams, and other goodies.
The 365HP mags respond well to a cam swap, exhaust upgrade, roller rockers, intake and carb. The old 420HP, 440HP, and 460HP 454 based mercury engines used basically a 365HP bottom end and heads. They got better exhaust, better valvetrains, intakes and carbs. If your gonna be using the 496 exhaust manifolds, I'd be careful with cam choice, from a reversion standpoint. They are a improvement over the old iron manifolds, but they aren't long riser'ed dry pipes.
In my opinion, what makes someone a good engine builder, is knowing combinations, and what each combination will produce. To be able to meet a customers budget, and most importantly, deliver a reliable product. HP doesn't mean squat if it doesn't stay together. In todays world, you can almost make 600HP from a big block chevy by accident. Making a 600HP marine engine that lives takes a little knowledge. I'm not gonna keep going back and forth on the whole oval vs rect port thing. I posted up a video of a buddy's old scarab III's setup, and Borgie seems to question the choice of parts used. Could he have made more power with different parts, surely. In that 10k lb scarab, 20HP doesn't mean $hit. He liked the look of the single plane intake, so we went with them. he could care less if the boat goes 65 or 65.8mph. But I can tell you this, that kid runs the ****T out of that boat every single weekend. Theres no cruising, its WFO everywhere he goes. Theres no issues whatsoever with the engines. A blown TRS, sure. But the engines run great, 89 octane.
10-14-2013 | 11:51 PM
#24
Banned
Joined: Jun 2013
Posts: 1,014
Likes: 0
From: AZ
Lets try to get back on track here. Turned into a which head is best, who knows engines and who doesn't, etc.
Lets talk about the 454 Mag for a minute. Its weak points are
Flat tappet sissy cams
GM 1960's castings for heads. They can work depending on your goals, but any good aftermarket head would be a improvement.
Exhaust Manifolds. They suck if trying to make anything over 375-400HP.
Intake Manifolds. They are decent, the old days cutting down the center divider and adding a 1" spacer helped them out.
Quadrajet carb. Great carb, but if serious about power, they can be limited, and tuning can be a little tougher than a holley.
Rocker arms. Stamped steel style.
Some of the strong points are
4 bolt mains
Forged Cranks
7/16 Dimple rods
Forged pistons
Now, I know your not at sea level, so that will change things. But, generally speaking, to get a Scarab III to run mid to upper 60's, is gonna take around 500HP per side. Mid to upper 70's, around 600HP per Side. In the 80's, 650-700HP per side. Once you establish what you'd be happy with as far as speed/power, then maybe we can start spending your money. If you'd be happy with 75-100HP increase per engine, there's really no reason to go spending 10k dollars worth of fancy aluminum heads, exhaust, roller cams, and other goodies.
The 365HP mags respond well to a cam swap, exhaust upgrade, roller rockers, intake and carb. The old 420HP, 440HP, and 460HP 454 based mercury engines used basically a 365HP bottom end and heads. They got better exhaust, better valvetrains, intakes and carbs. If your gonna be using the 496 exhaust manifolds, I'd be careful with cam choice, from a reversion standpoint. They are a improvement over the old iron manifolds, but they aren't long riser'ed dry pipes.
In my opinion, what makes someone a good engine builder, is knowing combinations, and what each combination will produce. To be able to meet a customers budget, and most importantly, deliver a reliable product. HP doesn't mean squat if it doesn't stay together. In todays world, you can almost make 600HP from a big block chevy by accident. Making a 600HP marine engine that lives takes a little knowledge. I'm not gonna keep going back and forth on the whole oval vs rect port thing. I posted up a video of a buddy's old scarab III's setup, and Borgie seems to question the choice of parts used. Could he have made more power with different parts, surely. In that 10k lb scarab, 20HP doesn't mean $hit. He liked the look of the single plane intake, so we went with them. he could care less if the boat goes 65 or 65.8mph. But I can tell you this, that kid runs the ****T out of that boat every single weekend. Theres no cruising, its WFO everywhere he goes. Theres no issues whatsoever with the engines. A blown TRS, sure. But the engines run great, 89 octane.
Lets talk about the 454 Mag for a minute. Its weak points are
Flat tappet sissy cams
GM 1960's castings for heads. They can work depending on your goals, but any good aftermarket head would be a improvement.
Exhaust Manifolds. They suck if trying to make anything over 375-400HP.
Intake Manifolds. They are decent, the old days cutting down the center divider and adding a 1" spacer helped them out.
Quadrajet carb. Great carb, but if serious about power, they can be limited, and tuning can be a little tougher than a holley.
Rocker arms. Stamped steel style.
Some of the strong points are
4 bolt mains
Forged Cranks
7/16 Dimple rods
Forged pistons
Now, I know your not at sea level, so that will change things. But, generally speaking, to get a Scarab III to run mid to upper 60's, is gonna take around 500HP per side. Mid to upper 70's, around 600HP per Side. In the 80's, 650-700HP per side. Once you establish what you'd be happy with as far as speed/power, then maybe we can start spending your money. If you'd be happy with 75-100HP increase per engine, there's really no reason to go spending 10k dollars worth of fancy aluminum heads, exhaust, roller cams, and other goodies.
The 365HP mags respond well to a cam swap, exhaust upgrade, roller rockers, intake and carb. The old 420HP, 440HP, and 460HP 454 based mercury engines used basically a 365HP bottom end and heads. They got better exhaust, better valvetrains, intakes and carbs. If your gonna be using the 496 exhaust manifolds, I'd be careful with cam choice, from a reversion standpoint. They are a improvement over the old iron manifolds, but they aren't long riser'ed dry pipes.
In my opinion, what makes someone a good engine builder, is knowing combinations, and what each combination will produce. To be able to meet a customers budget, and most importantly, deliver a reliable product. HP doesn't mean squat if it doesn't stay together. In todays world, you can almost make 600HP from a big block chevy by accident. Making a 600HP marine engine that lives takes a little knowledge. I'm not gonna keep going back and forth on the whole oval vs rect port thing. I posted up a video of a buddy's old scarab III's setup, and Borgie seems to question the choice of parts used. Could he have made more power with different parts, surely. In that 10k lb scarab, 20HP doesn't mean $hit. He liked the look of the single plane intake, so we went with them. he could care less if the boat goes 65 or 65.8mph. But I can tell you this, that kid runs the ****T out of that boat every single weekend. Theres no cruising, its WFO everywhere he goes. Theres no issues whatsoever with the engines. A blown TRS, sure. But the engines run great, 89 octane.
And for the sake of clarification I realize valvetrain is one of the most important aspects in any performance marine application, especially the big block Chevrolet. Takes good roller lifters, best springs you can reasonably afford, best pushrods, high quality retainers and locks, marine endurance roller rockers.... And blue printing everything. Inconel valves are a must on the exhaust side etc.... However you don't need to be an engineer or a veteran engine builder to assemble a reliable setup. I've seek plenty of " the best of the best" built by "Jesus himself" let go. S**t happens sometimes. But if it were a shade tree guy doing it, the failure resulted from his lack of marine building knowledge, all things being equal. Makes me laugh how people here eat this s**t up regularly.
Last edited by Borgie; 10-15-2013 at 12:03 AM.
10-15-2013 | 01:41 AM
#25
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Joined: Mar 2010
Posts: 458
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From: Las Vegas, NV
Well, I have plenty of time to think of what will be done. Pulling the motors this weekend and opening them up will give me a better picture of what's needed. Plus, I just spent quite a bit on bigger oil coolers, carbs and exhaust so need to recoup some $$. This will be an ongoing project with end date around the March-April 2014. For now, after motors are pulled I'll focus on redoing my bilge, painting outdrives and odds and ends while still deciding on a package for the build.
While I do appreciate all of the head combo suggestions if I do change heads they will be the Brodix aluminum heads. I found them to be the most affordable for a set of bare heads. Aside from machining and specific clearance checks that I may not have the proper tools for I plan on doing a lot of the assembly myself this time around. New valves will be on order no matter what head is used so I consider them a sunk cost as is. The springs come with the cam and the rest of the hardware is just that, hardware. Dolar for dolar a set of bare aluminum aftermarket heads for around 1200 is pretty good when doing alot of the work yourself.
While I do appreciate all of the head combo suggestions if I do change heads they will be the Brodix aluminum heads. I found them to be the most affordable for a set of bare heads. Aside from machining and specific clearance checks that I may not have the proper tools for I plan on doing a lot of the assembly myself this time around. New valves will be on order no matter what head is used so I consider them a sunk cost as is. The springs come with the cam and the rest of the hardware is just that, hardware. Dolar for dolar a set of bare aluminum aftermarket heads for around 1200 is pretty good when doing alot of the work yourself.
10-15-2013 | 01:47 AM
#26
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Joined: Oct 2000
Posts: 20,242
Likes: 2,490
From: Omaha/LOTO
I used a Holley 800 on a mildly hopped up 454mag with no problems.
10-15-2013 | 01:53 AM
#27
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From: Las Vegas, NV
10-21-2013 | 11:02 AM
#28
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Joined: Mar 2010
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From: Las Vegas, NV
Motors are out of the boat and in the garage. Going to do leakdown tests tonight on all cylinders to have a good idea across the board. Think I may have a buyer for a set of heads already. Check out the pics below. Pulling the motors was easy, set up and prepping boat for removal was the hard part.
[ATTACH=CONFIG]510506[/ATTACH][ATTACH=CONFIG]510507[/ATTACH]
[ATTACH=CONFIG]510506[/ATTACH][ATTACH=CONFIG]510507[/ATTACH]
10-21-2013 | 12:42 PM
#30
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From: Las Vegas, NV
3 6x6x14 planks make each column. the center board is cut down to fit a 2x8x12 which is the cross member. Everything else are 2x6's. All through bolted. I already recouped money spent on building this by removing the motors myself. Every place I called around here wanted $200-500 for ONLY removing the motors and this is after explaining to them that all mounts would be undone and ready to go. Rediculous!
