Tell me more about the 425 hp 454 engines...
#1
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Thread Starter
Tell me more about the 425 hp 454 engines...
I was intrigued by a recent thread where the poster showed pics of his new-to-him boat that had twin 425 hp 454 cid engines. Then I found another posting that showed Mercruiser engine power ratings from years ago. How in the world did they get those many ponies out of a 454?
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Baja 252 Islander
Baja 252 Islander
#2
Charter Member # 55
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All it takes is a cam, exhaust, intake and carb. I cloned my carbed 454mag to very close to 420/425 specs and picked up 400rpms. Another member closely copied my build and dyno'd his at 425hp
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bajaman (12-28-2023)
#3
21 and 42 footers
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What year is that chart?
On it the 454/425hp is categorized with the 540/575hp in the "performance products" section........wasn't the 575 simply a 540/500 wearing a small Weiand 256? If so, could the 454/425 simply be the same thing on the smaller displacement 454?
On it the 454/425hp is categorized with the 540/575hp in the "performance products" section........wasn't the 575 simply a 540/500 wearing a small Weiand 256? If so, could the 454/425 simply be the same thing on the smaller displacement 454?
#4
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I was intrigued by a recent thread where the poster showed pics of his new-to-him boat that had twin 425 hp 454 cid engines. Then I found another posting that showed Mercruiser engine power ratings from years ago. How in the world did they get those many ponies out of a 454?
a 450 hp 454
#5
Charter Member # 55
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The 420/425hp 454's were 454 mags that had the same cam as the 525SC, roller rockers, Holley carb, different intake manifold and Gil exhaust.
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bajaman (12-30-2023), William Diggens (12-29-2023)
#8
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I wonder why Mercruiser backed off so much on the power output of the 454s in later years? Especially considering the use of modern fuel injection systems and the ability to control so much more going on in the engine. The chart shows a relatively mild 8.8:1 compression ratio. So in this pretty much un-stressed engine, it was developing damned near 1 hp per cubic inch, pretty damned good for a carbureted normally aspirated engine!
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Baja 252 Islander
Baja 252 Islander
#9
I wonder why Mercruiser backed off so much on the power output of the 454s in later years? Especially considering the use of modern fuel injection systems and the ability to control so much more going on in the engine. The chart shows a relatively mild 8.8:1 compression ratio. So in this pretty much un-stressed engine, it was developing damned near 1 hp per cubic inch, pretty damned good for a carbureted normally aspirated engine!
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Throttles- Cleveland Construction 377 Talon
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Throttles- Cleveland Construction 377 Talon
08 OPA Class 1 National Champion
08 Class 1 Geico Triple Crown Champion
08 OPA High Points Champion
10 OPA Class 1 National Champion ( happy now Ed! )
#10
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I wonder why Mercruiser backed off so much on the power output of the 454s in later years? Especially considering the use of modern fuel injection systems and the ability to control so much more going on in the engine. The chart shows a relatively mild 8.8:1 compression ratio. So in this pretty much un-stressed engine, it was developing damned near 1 hp per cubic inch, pretty damned good for a carbureted normally aspirated engine!