Can a 454 put out 650hp on 9.5:1 compression?
12-11-2007 | 01:34 PM
#1
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From: Derby, KS
Can a 454 put out 650hp on 9.5:1 compression?
I'm looking at a 1988 38' Scarab that came with 420hp 454's. I'm told they're now putting out 650hp on 9.5:1 compression, bored out to 468 c.i.. I don't have all the engine details, although it's supposed to have LOTS of good parts, like Merlin heads, with no expense spared. It's a naturally-aspirated engine.
Is this possible? That seems like a LOT of hp for 9.5:1 compression.
Is this possible? That seems like a LOT of hp for 9.5:1 compression.
12-11-2007 | 02:39 PM
#3
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From: IL
I had a similar set up with my old engine - 468, Dart Heads, Eagle Crank and rods, JE pistons (8.5:1) I think and a Procharger at 5 PSI - 638 HP.
I doubt those engines are close to 600HP. Another wishful owner.
If the engines are good and the boat runs, who cares what HP they are!!
I doubt those engines are close to 600HP. Another wishful owner.
If the engines are good and the boat runs, who cares what HP they are!!
12-11-2007 | 03:02 PM
#4
Frank's Marine Service
Joined: Sep 2002
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From: Elkton, MD
I'm looking at a 1988 38' Scarab that came with 420hp 454's. I'm told they're now putting out 650hp on 9.5:1 compression, bored out to 468 c.i.. I don't have all the engine details, although it's supposed to have LOTS of good parts, like Merlin heads, with no expense spared. It's a naturally-aspirated engine.
Is this possible? That seems like a LOT of hp for 9.5:1 compression.
Is this possible? That seems like a LOT of hp for 9.5:1 compression.
To get in the 600 range you would need some good aluminum heads and spin in the 6K rpm range.
12-11-2007 | 03:04 PM
#5
21 and 42 footers
Joined: Sep 2004
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From: Richmond VA
Built 540's out of 500EFI's. Dart heads, 9.7 compression, monoblade intake, big cam.....made 630HP at 5,100 rpms (was told carbs would have added about 35HP since I'm restricting airflow). Did make 700 ft/ TQ though. 
12-11-2007 | 03:18 PM
#6
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From: San Diego
I used to own a Scarab that came with 454's also. Punched them to 468,big cams, heads ect. About 550hp. 650 can be done? , but.... it's going to be a very radical motor. Not very boat friendly. More of a strip motor. (still not too sure with 9.5-1).
Darrell.
Darrell.
12-11-2007 | 03:58 PM
#7
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From: Cleveland, Ohio
On a 468 with 9.5:1 compression I have made 625 HP N/A . Your not going to achieve this with rect. port out of the box cylinder heads though. 550 HP with 308 Dart Iron Eagles/Pro 1 310's and a hyd. roller camshaft is very achievable.
12-11-2007 | 05:13 PM
#8
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From: claymont, DE, USA
It can be done.
Heads would need to be fully ported
850 - 900 Carb
cam would need to be around a 250 intake 260 exhaust set on a 114 lobe center and separation.
That combo would make 650 hp between 5500 - 6000 rpm on 9.5:1
The problem is your torque would peak around 5000 rpm. That's just waaaaay too much cam for a 468 on 9.5:1
With a crane 236/244 112 610/632 you could make 640hp with an 800 and fully ported heads. Thats still too much cam though.
Dumb question; is he sure about 650? 550 would be so much more reasonable and believable.
Heads would need to be fully ported
850 - 900 Carb
cam would need to be around a 250 intake 260 exhaust set on a 114 lobe center and separation.
That combo would make 650 hp between 5500 - 6000 rpm on 9.5:1
The problem is your torque would peak around 5000 rpm. That's just waaaaay too much cam for a 468 on 9.5:1
With a crane 236/244 112 610/632 you could make 640hp with an 800 and fully ported heads. Thats still too much cam though.
Dumb question; is he sure about 650? 550 would be so much more reasonable and believable.
12-11-2007 | 05:23 PM
#9
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From: Cleveland, Ohio
It can be done.
Heads would need to be fully ported
850 - 900 Carb
cam would need to be around a 250 intake 260 exhaust set on a 114 lobe center and separation.
That combo would make 650 hp between 5500 - 6000 rpm on 9.5:1
The problem is your torque would peak around 5000 rpm. That's just waaaaay too much cam for a 468 on 9.5:1
With a crane 236/244 112 610/632 you could make 640hp with an 800 and fully ported heads. Thats still too much cam though.
Dumb question; is he sure about 650? 550 would be so much more reasonable and believable.
Heads would need to be fully ported
850 - 900 Carb
cam would need to be around a 250 intake 260 exhaust set on a 114 lobe center and separation.
That combo would make 650 hp between 5500 - 6000 rpm on 9.5:1
The problem is your torque would peak around 5000 rpm. That's just waaaaay too much cam for a 468 on 9.5:1
With a crane 236/244 112 610/632 you could make 640hp with an 800 and fully ported heads. Thats still too much cam though.
Dumb question; is he sure about 650? 550 would be so much more reasonable and believable.
take that Dean.
