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Thread: 454 MAG - MORE POWER !!

  1. #1
    OK guys, I have a stock Mercruiser 454 Mag EFI. What's the most dependable/economical solution to get more power from it ? Build it up ? Blower ? Supercharger ?

  2. #2
    It really all depends on how many $$$ you can spend and what your goals and constraints are. People have gotten great results by adding blowers (Whipples, Prochargers, or even small roots) to otherwise stock motors and limiting boost to just a few lbs to keep it safe. If you have more money to spend, you could do a full teardown, upgrade some internal parts, drop compression, and add a blower system with higher boost to make more power. Or, if you want to stay naturally aspirated, you could build something bigger and make power with better cam/heads/compression. Of course a key element to any method will be the exhaust system, so that's always a good place to start.

  3. #3
    Jeff, get the motor serial # & call Mercury marine in Stillwater, OK @ 405-743-6566 & just flat ask them what is in your motor! What is your max torque @ what RPM & HP rating @ what RPM, comp ratio, type crank, cam specs, ect. Get as much info as you can & depending on what is in your base package you can then add on to it. You need to know what it is in order to know where to start.
    The best bang for your buck is probably a cam & change the chip or have it re-calibrated if possible. I don't know enough about the Mercury EFI's to know if this is possible.
    If you could continue & do more I'd change the heads if your current ones are the small truck style heads with the little ports & valves to a bigger set that could complement a blower as a later addition. Remember, what RPM do you run at or want as a maximum? The wrong head & cam selection can kill everything. And for shitz & giggles maybe get Dyno 2000 or have a friend plug the #’s for you just play with your numbers & see what may have an affect on your motor. Not a real substitute for dyno testing but it will point you in the right direction. Also changing to full roller rockers will add around 15-25 HP & shed some oil temperature, maybe up to 75 degrees! That should make your motor happy also.

  4. #4
    gnarley, Are the 454 mpi's different from one to the next?
    What cam/head combo would you reccomend?

  5. #5
    [QUOTE]Originally posted by OC-PARTYCAT:
    gnarley, Are the 454 mpi's different from one to the next?
    They could be depending on year & other factors that only Mercury might know.
    What cam/head combo would you reccomend?
    It depends on what you want & what you got. & I'm not an expert here but different combo's work better than others so it always helps to hear from others who have already tried different setups & are willing to share the knowledge to prevent someone else from making the same mistake. It's one thing to hear someone say "oh just use this setup" I'm not that trusting, I want to see or hear real numbers.
    I for one would love to hear more information about what worked on what combo & how it did & if it wasn't a good choice, like well ok we won't do that again will we? Hey we all make mistakes don't we? Hell we learn from them so lets share our mistakes so others don't make the same ones.

  6. #6
    Procharger, you can find a used one for like 2500.00. Cam, heads. Would also do a great deal. I have a set of 500hp big rec port heads with Manley severe duty valves and springs for sale 800.00 if you have any interest.

  7. #7
    502,what do you think the heads would do to a stock 454 mpi? Lets say I put the heads on, a new cam, and a procharger in the future. Can the bottom end hold up?
    [ March 28, 2003, 12:18 PM: Message edited by: OC-PARTYCAT ]

  8. #8
    [QUOTE]Originally posted by 502procharger:
    I have a set of 500hp big rec port heads with Manley severe duty valves and springs for sale 800.00 if you have any interest.
    Nice heads if you want something that turns a lot of RPMs, but how often would you turn those RPM's. Probably real nice for 6500-7000RPM blasts but they probably flow a bit lazily where you run it most of the time. What RPM do you run at most of the time?
    Why are you selling them and what did you replace them with?

  9. #9
    The heads are off of a gen VI 500hp. I am building a new 540 and have dart pro 1 cnc ported heads on the way. I was going to go with the afr heads but they were 500.00 more and after 3 weeks on order i called them and they said 3 or 4 more weeks till i got them. What a bunch of crap. I was under the impression that the 500hp was made to run a 5400 or so top end rpm, why then would these heads be best at 6500-7000rpms? I thought these heads would be great for anyone looking to boost hp on a 454 or 502 BBC with smaller heads. Please correct me if i am wrong.

    [ March 28, 2003, 12:45 PM: Message edited by: 502procharger ]

  10. #10
    if you have small port heads, then these heads with a good cam, lifters and intake would make a big diff. if you already have big rec port heads then these would not be a large diff. if it is a mag, with a forged crank and 4 bolt main as it should be if it is a mag motor it will be fine with extra hp. i ran a stock bottom end in a 502 with 9lbs of boost for a while and never ever had an issue. I backed the boost down to 6-7lbs just to be safe though.
    not to spam you, but i have a 500hp cam and intake also, both used but good shape. i will sell it all heads, cam, intake 1100.00 + shipping
    [ March 28, 2003, 01:13 PM: Message edited by: 502procharger ]

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