454 MAG - MORE POWER !!

[THATJEFFGUY]

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 ?

[DogHouse]

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.
-brian

[gnarley]

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.

[OC-PARTYCAT]

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

[gnarley]

[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. :D

[502procharger]

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.

[OC-PARTYCAT]

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 ]

[gnarley]

[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?

[502procharger]

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.
http://www.hotboatpics.com/pics/data/500/1DSC03407-med.JPG
[ March 28, 2003, 12:45 PM: Message edited by: 502procharger ]

[502procharger]

OC-PARTYCAT
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 ]

[gnarley]

[QUOTE]Originally posted by 502procharger:
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.
Just my opinion, & from past experience with motors in general. The big square port heads flow fairly well, especially at mid-high RPM for stock heads but not low to mid. For low RPM the very small oval port/valve heads keep the velocity of the air/fuel charge flowing well at low RPM but just can't do it at high RPM. Other oval port heads have larger ports/volumes & valves that make them a better choice for low to mid range RPM’s up to 5500-6000. Best choice for 5500 & up are the big square port heads, it's all about air flow. Your new ones should be nice but myself I would be concerned about what RPM they are best suited at.
Back to your old heads, what cam was in that & matched to your heads & comp? Just remember Mercury isn’t in the business to build custom engines they make a few flavors that are supposed to cover all bases, they don’t. And what they sell they must warranty if you break it so they build them without combinations that might break something & limit how many RPM’s they turn. Built the right way a 454 can easily push 600 HP & 600 lbs ft torque, but you knew that right and a 502 even a bit more. So what are you trying to do with your new combo & what RPM’s will you run it at?

[502procharger]

Gnarly
Thanks for the info. I do not have my old cam spec's here but i will get them. Why does no company have a variable port head? You could get the benefit of the best of both worlds. I know many 2 stroke motors have variable exhaust ports for that reason. I would think someone could design a head that would give you a small port for low-end power and torque and open as rpm increase or something like that.
As for my new motor, i am just building a stout motor for one of my boats. It is a 25' Switzer with an xr drive. Should run about 900hp at 9lbs of boost. Give or take a little. All good stuff in the lower end also. I built it to last. I like the procharger because the build very little boost low end and are much easier on the drive, but give you a kick ass midrange and good top end. Should be a good setup. Not really sure how fast a 3600lb v bottom will be with 900hp, but should rum well.

[gnarley]

[QUOTE]Originally posted by 502procharger:
Gnarly
Why does no company have a variable port head?
Actually a few have played with them if I remember right, like in the 4 valve per cyl engines. They leave 1 port closed off & it opens at a given rpm for the mid range-topend. I think the new corvette does that, I think the Misubishi VR 3000 twin turbo did it as well as the stealth with the same engine & maybe the SHO Taurus

[502procharger]

ironicly i have a 3000gt vr4 it is 4 valves per cyl. twin turbo, awd, aws, but i knew nothing of variable valves.

[OC-PARTYCAT]

so do I need rectangualar or oval ports for my application. I dont think the motor is going to turn more than 5.5k. The boat weights in at about 4500#. Its got a bravo III hooked up. Im not sure but doesnt the engine (99 454 mpi) have a roller cam set up already.

[502procharger]

I guess it is really your choice, the oval ports are going to give you good low end and mid range and not be as good on top, the rec port heads will give you less low end but still have good mid and high end. I went through this on a 454 I had but it was a carb motor and i do not know if it makes a difference. I went with rec port Merlin heads and dart intake, in my boat it really woke it up.

[OC-PARTYCAT]

If mid range is 3k, and top end is 5.5K I think I would prefer the rectanular. I dont care if the boat doesnt jump out of the hole as long as it gets up on a plane like it does now, I would be happy

[gnarley]

[QUOTE]Originally posted by OC-PARTYCAT:
so do I need rectangualar or oval ports for my application. I dont think the motor is going to turn more than 5.5k. The boat weights in at about 4500#. Its got a bravo III hooked up. I’m not sure but doesn’t the engine (99 454 mpi) have a roller cam set up already.
I think I'd go with a nice set of oval port heads matched to a cam that makes power in the range you need it. Not the little oval port heads.
It's funny, as I'm going through this myself right now & I only want to twist it up to 5500. My engine needed to come out for some drive repair, so I thought GREAT I can finally see what’s in it. I found a tag & found the engine was a Merc & not an OMC. I called Merc & got the numbers & that made me sick! Then pulled it down & got the cam #'s that was better but didn't work well with my heads! So I'm installing a larger set of oval's that seem to work better with my cam based on the Dyno 2000. Again as I have said it's no substitute for real Dyno testing if you can, but it will point you in the right direction. Changing heads netted about 175 HP increase & 70 for torque so said the software. What I saw from the software was even with blower cam the heads were too restrictive, so change the heads & more airflow! That sounds almost like what you want. If the numbers are even close it will be a mid range torque monster & make good top end HP to the range I want! But a warning that the BIII might not take it!
[QUOTE]Originally posted by OC-PARTYCAT:
If mid range is 3k, and top end is 5.5K I think I would prefer the rectanular. I dont care if the boat doesnt jump out of the hole as long as it gets up on a plane like it does now, I would be happy
5000 on up is just the beginning of top end. Ask others what they think & would be the best choice of heads for your needs. I think the Rectangles are to big.
JMHO
WHats your email?
[ March 28, 2003, 04:10 PM: Message edited by: gnarley ]

[502procharger]

Gnarly knows his stuff, but i went with the rec port merlins and the motor was very strong. I guess there are many other variables that fit into the equation like cam, mpi or carb, ECT. I am just going from my experience. I think you will get some good hp gains with either.

[gnarley]

502pro I think you'll still be happy & will see good increases but think your giving up to much mid range & moving it up the scale where you rarely will use it & may not see what those heads are really capable of doing. Torque gets things moving & HP keeps them moving, having all the HP in the world doesn't do much if you rarely or never use it. I liken it to soo many guys I’ve seen build street engines & put way to big cams in, bigger isn't always better. I hope it works for you, let us know how it works.

[OC-PARTYCAT]

Thanks for the help guys. After this season (if not earlier) Ill get a good set of heads and cam.
If im reading this right..I can make the motor about 575hp with a good set of oval heads,cam,intake, and exhaust right?? Ill probably run that set up for a season then go with a new drive and procharger and freshen up the bottom end. Im thinking my goal would be about 800 reliable hp. If the 454 mpi has a steel crank I should be ok..I think. but the b3 would be on e-bay. :p

[gnarley]

575 HP for a set of oval's should be no problem, but if you want to get to 800 with those oval port heads I don't think it will happen, it might, but I think you'll be really pushin things to get that power from a set of oval heads, do you paln on buying 2 different sets? I guess if I were doing a 2 step upgrade I'd buy the bigger heads now for the planned usage later.

[powerplay230]

I know rectangle port heads are for higher rpm's, but believe they come standard on all the magnum engines, both 454/350hs and the 505/415. Remember how much harder a boat engine works than automotive and the amount of air it moves! On my street motor I have a set of the big port ovals that have had a lot of work done. Boat motor is a 502/450 longblock that came with the "square ports" Oval ports such as Edelbroch's or others are a far cry from GMs

[gnarley]

Agreed, boat engines work harder! But it doesn't matter what the engine is in for air flow, a car or boat, the air needs of the engine at a given RPM are no different, 3000 is 3000 & 5000 is 5000, it’s just an air pump! But not knowing something has provoked a thought. IF GM only provides 2 choices in heads on its base gen V & VI marine engines then what do you get or do when buying factory iron? The small port heads aren't enough after 4500 RPM so maybe the only alternative from the factory is the square port head which out flows the smaller oval port heads & let the motors run past 5K. It would be interesting to see flow specs on the factory square port heads as compared to real good ovals & real good square ports.

[502procharger]

gnarly, that’s kind of what i was wondering, i thought all gm 91 and up 502bbc heads were rec port.
Why would they do that if the oval port worked better on those motors? My stock 500hp heads were good for 634hp at 5900 rpm's on a 540 i had so they are capable of making good hp. I obviously had a diff. Cam, roller rockers and lifters, ECT. I do not have the torque numbers in front of me but i will post the dyno sheet when i dig it up. Why does gm not use oval port heads? Just wondering.

[gnarley]

Maybe the 502's only get the square ports? Do they on the truck line? It would be nice if a GM tech would enter here & straighten this out. :)

[powerplay230]

Newer Big blocks- 502's come with square ports, Mercs 454 come with Oval ports on base motor and Square ports on the magnums. The oval ports have "nail head" valves (tiny) and smaller runners and ports. Some of the oval ports can be made to run like a bat out of hell. In my Chevelle I have a pair off a 454/360hs that have been ported and larger valves put in, that motor spins at 6500 without any problems. My old boat motor was a base 454 with Ovals (stock) and if it turned over 4500 rpm I would run out and buy lotto tickets. I know nothing about the dart/world etc.. but if Merc uses the square ports on all the performance motors it can't be a bad start. Also have heard the Edelbrock ovals work pretty well. But then again I'm not one of the boys that can afford a big hp motor frown

[powerplay230]

Think Gnarley has the best idea- play wiht different combos on a dyno program then go to a recommended engine builder and run it buy him. What part of the country are you in? You also need to think about operating range of your drive, you don't want to run a Bravo at 7k rpm

[gnarley]

[QUOTE]Originally posted by powerplay230:
you don't want to run a Bravo at 7k rpm
That’s kind of my point. How many of us have all the hardware & money to build then operate at those RPM's frequently? I want to have fun & not work on the boat all summer long, I only have so much time to work on my fleet & don't want to break the bank or myself. It just seems that pushing over the 5500-RPM boundary starts to encourage wear & tear on something. Building it to run 6500+ RPM's is just like pouring money into the water since those RPM's are rarely seen unless racing. Bullet proof is one thing but over built for the wrong operating range is another. We all have our own desired operating ranges, so for me as much power as I can build on a budget up to 5500 is good. Maybe this would be a good survey; What RPM do you run at most times and how often do you run 5000, 6000, 7000 RPM’s?
http://forums.***boat.net/ubb/ultimatebb.php?ubb=get_topic;f=1;t=005102
[ April 01, 2003, 07:59 PM: Message edited by: gnarley ]

[powerplay230]

If anyone has money to pur into the water I have a better place. At least better for me! :D