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Replacing 330hp 454 with 365hp 454 mag?

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Old 04-19-2011, 09:26 AM
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Default Replacing 330hp 454 with 365hp 454 mag?

I'm looking to replace the 330hp 454 in my 88 Formula 242LS with a used 89 454 MAG. The MAG doesn't come with any ignition parts, flywheel or accessories should all of that be the same for both engines except the ignition box? Thanks.
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Old 04-19-2011, 12:06 PM
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Is something wrong with the original engine, or are you just looking for more power? If it's more power it seems like an awful lot of trouble for a minimal gain.
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Old 04-19-2011, 12:12 PM
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Originally Posted by Crossett View Post
Is something wrong with the original engine, or are you just looking for more power? If it's more power it seems like an awful lot of trouble for a minimal gain.
It's not just the Hp gain, the 365 Hp mag motor has forged internals. That alone is worth the swap. I would do it in a minute if I found two cheep 454 Mag motors.


That said, he's also looking to upgrade the HP in the mag motors, and use the forged internals. You can only build the 330Hp motors to approximately 420ish HP before you have to start seriously worrying about your lower end. The 365 HP mag motors, with forged internals, can be taken to 500-550 HP before the same worries start kicking in.
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Old 04-19-2011, 12:28 PM
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Originally Posted by CenturyUltra View Post
I'm looking to replace the 330hp 454 in my 88 Formula 242LS with a used 89 454 MAG. The MAG doesn't come with any ignition parts, flywheel or accessories should all of that be the same for both engines except the ignition box? Thanks.
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Old 04-19-2011, 01:21 PM
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Originally Posted by wjb21ndtown View Post
It's not just the Hp gain, the 365 Hp mag motor has forged internals. That alone is worth the swap. I would do it in a minute if I found two cheep 454 Mag motors.


That said, he's also looking to upgrade the HP in the mag motors, and use the forged internals. You can only build the 330Hp motors to approximately 420ish HP before you have to start seriously worrying about your lower end. The 365 HP mag motors, with forged internals, can be taken to 500-550 HP before the same worries start kicking in.
The pistons and rods in the 330 are forged, the crank is not. And 420 horse before you have to worry about the bottom end seems kind of low to me.

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Old 04-19-2011, 01:29 PM
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Yes it should, ignition too. The one thing is its nice to get the flywheel/balancer balanced to the rotating assembly but if you are not tearing down I think it will be just fine anyway. I had 365hp mags originally and ended up with 330hp remanned shortblocks that I used the flywheels/balancers on from the 365.

A word to the wise though is watch corrosion in the water jackets on a 20+ year old marine block. It could be bad or if it had cc, could be no problem at all. My 365s where bad and that was 10yrs ago.
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Old 04-19-2011, 01:36 PM
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Originally Posted by Crossett View Post
The pistons and rods in the 330 are forged, the crank is not. And 420 horse before you have to worry about the bottom end seems kind of low to me.
Very low in my book too. The rod bolts were the weak link at 3/8" vs the mag engines 7/16. The 330s had cast pistons but they would take a beating just fine. The crank you wouldn't want to spin to 6000rpm but it could make good power around 5000rpm and live as long as the assembly was stout.
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Old 04-19-2011, 01:37 PM
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Originally Posted by Fountain4402 View Post
I dont really see the point unless your other engines is broke. 30-45hp is such a minimal gain. Your better off only bringing a 12 pack on board then a 24 pack, you would save weight and probably get more speed that way
He wants to put a small blower on it.
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Old 04-19-2011, 01:47 PM
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Originally Posted by Crossett View Post
The pistons and rods in the 330 are forged, the crank is not. And 420 horse before you have to worry about the bottom end seems kind of low to me.
No, the 330s do not have forged lower components. They have cast pistons and the smaller rods. Some people have gotten 500hp out of them, but personally I think they're playing with fire. I would upgrade at least the pistons and rods before pushing it that far.
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Old 04-19-2011, 02:02 PM
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Originally Posted by PARADISE ISLAND View Post
I'd go for it rectangular ports roller cam better motor!
The 365hp has flat tappet cam. PI is right though, you could make a ton more power with that rect port engine.
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