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Whats my 454 Merc???

Old 01-16-2013, 09:49 PM
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I thought all non mag 454 engines after 1996 had roller lifters and vortec cylinder heads??? I thought they stopped making the old peanut ports after 1995.
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Old 01-16-2013, 10:17 PM
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maybe gm had a ton of left over peanut port heads,so they unloaded them on the engines being sold to mercury.
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Old 01-16-2013, 10:25 PM
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Originally Posted by mike tkach
maybe gm had a ton of left over peanut port heads,so they unloaded them on the engines being sold to mercury.
Quite possible. Now that I think of it, maybe they did because gm didn't make a carbed intake that would match up to the vortec head ports. They were larger ovals rather than the little peanut port ovals on the mark iv and gen v engines
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Old 01-17-2013, 02:09 AM
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They must have had a $hit load of'm. '96 and '97 had carbs,TBI, and MPI. Mags only had carb or MPI those two years.
All MPI's starting in '98.
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Old 01-17-2013, 10:12 AM
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Those years are really confusing. You pretty much have to go to the parts schematics and look up the engine by serial number, then get the part number off the listed head to figure out what it actually came with. They mixed a lot of parts until 98 when they just offered the 7.4 MPI or 454 Mag. That's what I did to confirm Spooln had the peanut heads.

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Old 01-17-2013, 10:30 AM
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What I learned from this thread - trying to determine what 454 you have is a pain in the arse and even if you think you have a mag because of rectangular ports you still may not. Serial numbers lead in all kinds of directions and there is nothing on the internet that definitively helps. Boating sites are useful but sometimes are the equilivilant of chasing your tail. If you go to contortion class and buy a magnet and camera you can get more casting/serial numbers, determine if the intake is steel or aluminum and take photos so that someone somewhere may be able to tell you something!!!
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Old 01-17-2013, 11:21 AM
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Ok Had time to jump in boat last nite. Here we go cast # to block 10237297 Found out yes correct Gen VI w/vortec heads thats what I got so far. Also intake is cast did the magnet thing. So I assuming 330hp motor?
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Old 01-17-2013, 11:38 AM
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Also I have access to pair of 781 heads are they good heads and fit my block ok ?
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Old 01-17-2013, 03:52 PM
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Originally Posted by Spooln
Also I have access to pair of 781 heads are they good heads and fit my block ok ?
IF you really have the Vortec heads, and not the peanut ports, and you bolt on a pair of 781 ovals, you will lose about a full point of compression. The vortecs have a small chamber compared to most other open chamber bbc heads. Going to any other head without changing pistons, wont help much. Whatever power you may gain from a airflow standpoint, you'd offset with the loss of compression.

The vortec heads aren't bad, and considering you probably have a cast crankshaft, and 3/8 rods, you wont really want to turn more than 5000RPM.

Basically what you have there sounds like a standard L29 454 Truck engine. The cam in them is pretty anemic. They are something like 204/209 480 ish lift, and if I remember right, installed quite a bit retarded.

You can drop in a cam from a 502/454 mag roller engine, 224/224....usually you can find these cheap on oso, and still use your current lifters. Anything aftermarket with more lift will require a lifter change, I think.

Theres a few things you can do to the vortec heads to improve airflow, I know the intake ports can use a little cleaning up. I want to say a edelbrock performer dual plane intake will line up ok on those vortecs.

A little work on the heads, cam and intake swap, better set of aftermarket exhaust manifolds, and I think you'll be somewhere in the 400HP range.
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Old 01-17-2013, 04:14 PM
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Thanks Mild
Would that motor be ok with a 177 blower 5-6lbs?
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