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How do you tell if a 454 is a mag or not?

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Old 11-02-2009, 12:46 AM
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Default How do you tell if a 454 is a mag or not?

The boat is a 1991 larson senza and I was wondering how i can tell if the engine is a 454 mag or just a 7.4L?
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Old 11-02-2009, 12:52 AM
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the 7.4 has oval port heads,the mag has rectangle port heads
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Old 11-02-2009, 12:53 AM
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Is there a way to tell well the engine is installed in the boat?
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Old 11-02-2009, 07:14 AM
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Serial number. Look on the back of the block, I believe on the right side.
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Old 11-02-2009, 09:21 AM
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Is there a certain digit or anything?
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Old 11-02-2009, 09:41 AM
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Metal tag on motor is ORANGE (rather than purple).

I think..............

It should be fairly well marked. That vintage, if it just says "7.4L Bravo I" on the spark arrestor, it's NOT a mag.
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Old 11-02-2009, 10:57 AM
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The intake manifold is raised higher towards the carb ,where a 330 oval port has a more flatter intake manifold,if parts (manifolds )has been swapped on engines its difficult to say ,but there is a way to see if the heads are retangular or oval port , on the end (front/rear side ) of each magnum/retangular cilinderhead there is a bump in the castingline ,all steel retangular port heads have these ,,bump,, where the ovals have a flat castingline ,see if you can find a magnum head ,and look for the bump you,ll see what I mean .
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Old 11-02-2009, 11:24 AM
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and to confuse things a bot more the 454/ALPHA available for a few years were called Magnums even on the airclaner but were just plain ole 330s not real Magnums.
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Old 11-02-2009, 11:53 AM
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Quote:
Originally Posted by twistedvelocity View Post
Is there a certain digit or anything?
There probably is a designated letter or number, or combination of such, that would determine whether it is a Mag or not. However I don't know what it is. If you give the number to a dealer they will be able to tell you. You may even be able to look it up on-line.
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Old 11-02-2009, 12:39 PM
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Quote:
Originally Posted by twistedvelocity View Post
Is there a certain digit or anything?
No.

The magnum engines have a high rise aluminum intake. The 7.4's have a steel low profile intake. If you pull a valve cover, the rect port heads say "Hi Perf" inside.
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