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Thread: 454 MPI rebuild

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  1. #1
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    454 MPI rebuild

    So I took my boat in for repair and while I was there my mechanic asked me if I wanted to see some brand new rebuilt engines he was installing in a 29 Outlaw. The motors that were rebuilt were the same motor that I have in
    my 252 he said. The motors were changed though from EFI to carburated. Twin 454's at 330 HP rebuilt and now get 550 hp. The mechanic told me that the man who rebuilt the motors said you get better performance and HP
    by using carbs. The motors had high rise intakes and one 650 Holley each. The motors were done by Earl Johnson. A big name in my area I was told. So my question is it true that you get better performance by going carbed over EFI/MPI?

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    Baja Supporter tablerocker's Avatar
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    Re: 454 MPI rebuild

    lol...almost as good a forum question as "which oil is better....".

    I would say that GENERALLY speaking, a carbureted engine, especially a normally aspirated one, CAN be more "powerful" insofar as maximum horsepower is concerned, over a fuelie. Once forced induction comes into the picture the fuel injected engines GENERALLY speaking are more powerful, due to their ability to precisely meter fuel and react instantaneously to changes in load, boost, air temp, etc etc.
    A fuel injected engine will almost always be more 'efficient' due to the precise fuel metering. Some 'confuse' efficiency with power erroneously.
    I'm 58 years old so I well remember the top engine builders, the guys with the 'fast cars' building some insane engines for the day. A 600 hp big block Chevelle roamed the streets as well as some hemi 'Cudas and Challengers, and a crazy fast Torino with a Super Cobra Jet 428. These guys were always tinkering, tuning, and racing each other. I guess the point of this rambling is...yeah, a carbureted engine can make serious power. I'm not sure if any of those engines, being not designed from the ground-up for fuel injection, would benefit or be any more powerful.
    Table Rock Lake is my home away from home, and big block power rules.

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    Baja Supporter JerseyOutlaw's Avatar
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    Re: 454 MPI rebuild

    Quote Originally Posted by Pauly View Post
    So I took my boat in for repair and while I was there my mechanic asked me if I wanted to see some brand new rebuilt engines he was installing in a 29 Outlaw. The motors that were rebuilt were the same motor that I have in
    my 252 he said. The motors were changed though from EFI to carburated. Twin 454's at 330 HP rebuilt and now get 550 hp. The mechanic told me that the man who rebuilt the motors said you get better performance and HP
    by using carbs. The motors had high rise intakes and one 650 Holley each. The motors were done by Earl Johnson. A big name in my area I was told. So my question is it true that you get better performance by going carbed over EFI/MPI?
    I pulled an efi motor and went to carb. I was searching for more hp, but the carb decision was to reduce points of failure mainly because im in saltwater. I want fuel and spark. The fuel difference in efficiency was barely noticeable at cruise speeds, I little more noticeable at WOT but I also went up in horsepower. My advice to you would be, forged pistons/rods/crank, stainless steel valves, roller cam and rockers. Be very careful on cam choice because reversion becomes an issue on cam design/custom grinds unless your splurging on dry exhaust. I have a JRC custom ground cam in mine, zero issues, great manners at idle and sounds fantastic. I had a friend of mine build a 330hp 454 carbed motor with the upgrades you're considering, he had alotta fun with it.

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    Re: 454 MPI rebuild

    Have to agree 100% with "less technology is more desirable sometimes". Lots of things to go wrong with FI, carbs are simple creatures and pretty much bullet-proof.
    Table Rock Lake is my home away from home, and big block power rules.

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    Baja Supporter stude's Avatar
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    Re: 454 MPI rebuild

    As far as horsepower, you should be able to get just as much from efi as a carburetor. The problem is that it seems hard to find someone to do tuning on Marine efi for high performance applications. I am just lucky enough to have a friend that does tuning.


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    Baja Supporter tablerocker's Avatar
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    Re: 454 MPI rebuild

    lol...yeah, just like the guys I grew up with that "knew what to do" with cams, carbs, headers, intakes, etc...the new generation of tuners sit behind a laptop and work wonders.
    Table Rock Lake is my home away from home, and big block power rules.

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