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how to tell if I definately have a magnum motor

Old 07-27-2009, 09:59 PM
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Default how to tell if I definately have a magnum motor

I just got a new to me Baja boat, its an 87 and the previous owner had paperwork that showed he had a new motor installed in 2005,
its supposed to be a 2001 Merc Magnum 454 motor,
I checked the casting number on the bellhousing and the numbers are
12550313
which state according to a search on here thats its a
454.......91-up...4-bolt, Gen.V crate motor, Gen. VI 4.25" bare block, fuel pump boss

there is also D050 cast in to the bellhousing as well,

what else should I check for
the carb flame arrestore says 454 merc magnum on it but I konw that can be from anything

just trying to verify exactly what I have because I would like to possibly upgrade to a bigger cam, new intake manifold and bigger carb very soon like in a few days if possible

thanks for any help
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Old 07-27-2009, 10:39 PM
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you can pull a valve cover also and see what heads you have. sounds like it's a magnum with the forged internals, 7/16 rods. no real way to be certain with out doing a complete pull out and drop the pan. i doubt anyone would put a cast crank in a 4 bolt block. does it look like it has been apart? Look near the front and rear sealing area of the intake as well as bolt heads for signs of being apart before.

regardless pull a valve cover to see what heads you have and persue your upgrades. there are numerous threads pertaining to 454 upgrades or roids. if you need some help email me and i will help you.
john
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Old 07-28-2009, 07:44 AM
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Originally Posted by getrdunn View Post
i doubt anyone would put a cast crank in a 4 bolt block. l][email protected][/email]
I have never seen a two bolt main in a marine BBC engine. Example look at the 330HP Mark IV that have been around for ages, that cast internals and 4 bolt mains.

And I have been around ages

Also the true 454 mags had Rectangular heads not the small ovals. That might be your best sign.

Last edited by 1BIGJIM; 07-28-2009 at 07:46 AM.
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Old 07-28-2009, 08:05 AM
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Didn't the 330 have a cast iron intake? The mag has an aluminum intake with a bronze insert in the water jacket
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Old 07-28-2009, 03:37 PM
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The 330 has a cast iron intake. Not sure about the Mag. Pull a valve cover and get the casing number. If you upgrade the cam don't forget the aftermarket exhaust. Be sure to get long risers to avoid reversion. Be sure you also upgrade the oiling system. These are things I did not do first and blew it up 3 times before getting it worked out.
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Old 07-28-2009, 03:49 PM
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The old 454 330 HP were two bolt mains. The Mark IV blocks with 4 bolt mains have two of the same size pipe fitting just above oil filter boss. If one is smaller that other its 2 bolt mains. If your intake runners almost touch the valve covers you have sqare ports heads (used on Mags and higher HP motors) If your intake runners are about 1/2" lower than you have oval port heads. Those are a couple of way the try to figure out what you got without taking anything apart. Hope it helps.
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Old 07-28-2009, 04:54 PM
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Originally Posted by Clustergear View Post
The old 454 330 HP were two bolt mains. The Mark IV blocks with 4 bolt mains have two of the same size pipe fitting just above oil filter boss. If one is smaller that other its 2 bolt mains. If your intake runners almost touch the valve covers you have sqare ports heads (used on Mags and higher HP motors) If your intake runners are about 1/2" lower than you have oval port heads. Those are a couple of way the try to figure out what you got without taking anything apart. Hope it helps.
My 330HP 7.4L 1994 was a 4 bolt main. I have not heard of any 2 bolt main BBC marine blocks. Thats not to say they do not exist. What years were the 330's 2 bolt mains? The easiest way to tell is to get the numbers off the block and check mortec.com for the specs. Even with that info you can not be sure of cast or forged internals if it has been rebuilt.

Last edited by jeffswav; 07-28-2009 at 04:58 PM.
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Old 07-28-2009, 07:25 PM
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block is definately a 4 bolt block I checked the casting numbers its
12550313

I just checked the heads and the casting numbers are # 10114156
which casting is this
and are they any good ?
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Old 07-28-2009, 08:02 PM
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Originally Posted by jeffswav View Post
My 330HP 7.4L 1994 was a 4 bolt main. I have not heard of any 2 bolt main BBC marine blocks. Thats not to say they do not exist. What years were the 330's 2 bolt mains? The easiest way to tell is to get the numbers off the block and check mortec.com for the specs. Even with that info you can not be sure of cast or forged internals if it has been rebuilt.
there are several 454/330's with 2 bolt mains as well as cast internals. why and when merc decided to do so is another question. i wouldn't say this unless i knew for sure. two of my own personal boats in 78 and 92 both had 2 bolt mains and cast internals. both boats had original engines.

john
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Old 07-28-2009, 09:29 PM
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Per Mortec.com

10114156...91-up...oval...OPEN...Gen.V & VI 454, 118cc chamber

They sound like large oval ports.
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