454 Mag modded Or stroked with non forged internals ?
 

Opinions please ! New here. I have been reading a great deal on this subject. Two years ago I purchased my boat , took it out for my first run and spun a bearing ! So I finally am able to bring the engine to a builder. I figure this engine will be my core. He suggested an engine he has , a 454 mag , of course all forged internals , says we could work it up just short of 500 HP and be fine for the weight of my boat. We also discussed the idea of building a stroker with my block. Internals will not be forged as the build would be over my budjet. I would love to have the low end torque , but I'm leaning towards the less expensive and forged Mag build . Anything that can help my confidence with a decision would be greatly appreciated !

Id go with the mag, you should be able to get a tad over 500 with a better intake carb and roller cam

Thanks , I just want to be in a good standing later by doing it right , now.

Go with the Mag. Much better off in the long run.

then get your crank cut and buy a set of good used pistons-rods from another 454 mag out of the swap shop here and have a spare engine ready to go...

Ask yourself, are you going to want more power in the future? If so, then it gets a little more complicated, I think. If you go the mag route then later you can add a blower and be good. If you stroke it now, to add more hp later would warrant upgrading to forged for the added safety. Not sure I completely answered your question but I don't think it's as "black and white" as it seems when asked.

I'd go with mag

Thanks for your input. I have decided the mag build will be the best route. Now I'm trying to decide if I will try to invest in a roller can. This build just keeps costing more and more ! Lol. I'm wanting to save the extra 400 over a flat tappet upgrade. I'm really scraping the money together to get this boat on the water this year ! But , its all I can think about !

I know what you mean. I've been there three times myself and currently going through it right now by adding blowers to the motors I built last year. my advice is to always think ahead. If you go a certain cam now to save a few bucks and later decide to upgrade to a different cam that you originally passed on, how much more $$ are you out on two cams and pulling engine, ect.

Ha, you didn't get a boat to save money right?

You will do much more with a roller. and a much less chance of wiping something out. If its that tight. fix what needs to be fixed in the motor and run it/ run the stock mag. SAve your money for gas. Save money to either eventually build the motor you want of get a faster boat to begin with.

100% agree. My advice was only intended if you are set on building something but if the mag is all good just run it and have fun.

Haha , Save money ? Point made ! I bought my house almost a year ago , for closed , everything needs attention ! But I moved here BC I'm 10 minutes away from my favorite body of water. That boat is going to be on it this year ! I feel like I won't be happy without going roller ! Any suggestions on what to use ? Also , I know everyone says to throw away the stock exhaust ! They put these manifolds stock on 502's , what will these manifolds be ok to use up to , about 450hp ? I certainly won't be able to do exhaust this year also.

Go with the Mag and a roller cam. What exhaust do you have? If you have the factory Merc exhaust you won't be able to run a big enough cam to get 500HP out of the Mag due to water reversion. You will only get around 400HP with a cam suited for the factory Merc exhaust. I was also on a budget with my build. I didn't have the money to build the new engine and buy performance exhaust. I got 407HP out of my engine ran it for 2 years with factory Merc exhaust with no reversion problems. I have had Gil exhaust the last 2 years but it runs so good I don't want to bother putting a bigger cam in it.

So , I talked to the builder. He says , well u should think about a cam upgrade now, there are much better grinds then what can in the motor. I agree with this , so then the questions came with what route to take with this cam. I really can't see taking this motor further then na for this boat. But I'd like to do it right the first time and save money in the long run. Is it worth me asking a guy I've read about , Bob Madura for a custom grind ? Or is this considerable more cost ?

Decide what exhaust you are going to run before you pick your cam. Yes Bob is the man and worth every penny! I'm going to use him for my next build.

It's better to take a year off than it is to face many years of misery.

IE: better to do it the way you want and should vs making bad choices in order to get on the water earlier.

Just sayin.

I'm running the Isky 270/280 Mega hydraulic cam with Scorpion Racing 1/7 roller rockers. I made 407HP on the dyno. I had no reversion problems with factory Merc manifolds. I think that is about as big as you can get with factory manifolds. I'm sure Bob can grind you something similar in a roller and you might get a few more HP.

http://www.flatlanderracing.com/iskycamsmarine.html

put the mag in stock, enjoy the summer. keep your eyes open for used exhaust, intake etc on here and FB. once you have collected some parts, exhaust, intake/carb then you can work with Bob or somebody and match a cam to what you have and maximize your gains.

This is a marine engine, you are going to ask it to work hard in an inhospitable environment, It needs to be built right with the right parts, It is not a 74 camaro with pep boys dodads and 99.95 black jack headers with cherrybombs. If it goes boom, you dont just coast over to the side of the road, you could very well be stuck in the middle of lake michigan in very ugly conditions,

You CAN build a 500 hp 454 easily and fairly economically too but it has to be done RIGHT or you will get disillusioned at spending 3 times what you needed to while sitting on the dock because your chit is broke You currently do not have the dollars or knowledge to do it right. No disrespect intended, its just the way it is, we have all been there,

Put it together with a stock mag, should still get you low 60's which isnt bad, While you are enjoying it figure out exactly what you want and how to get it.

Yup. Don't do an aggressive roller cam until you can get better exhaust at the same time.

Thanks to all for your sincere advice! I have taken note of several good points. My builder is very knowledgeable and has been great with it all. He's building 25k motors for guys who probably are less hassle then me ! Lol. What is , when I first called him, he mentioned a mag motor that was very fresh a guy had sunk , turned it in for a core . Builder said he'd sell for a good deal all gone through , intake to oil pump. So , I wrote a check to get it all going. I'm excited and want to make the right steps at the right time. Getting advice , helps me see the ( big picture ) as I go through the process . Thanks to all , I would appreciate any further comments.

hyd roller cam won;t break the bank and can run it with existing valvetrain. 112 LSA is the limit for stock GM exhausts. http://paceperformance.com/i-6254922...oller-cam.html

That cam has the following specs at .050" if installed at 108ICL
211° Intake Duration / 230° Exhaust Duration
112° LSA
Events at .050": IVO -2.5° BTDC / EVC -1.0° ATDC
Overlap -3.5°

And your saying the following cam will revert more because of the 110LSA ?
This cam has the following specs at .050" if installed at 110ICL
214.5° Intake Duration / 219° Exhaust Duration
110° LSA
Events at .050": IVO -2.5° BTDC / EVC -1.0° ATDC
Overlap -3.5°


Note: the two different cams have the same IVO/EVC Events and Overlap at .050".
The second cam has more intake at .050" duration, tighter (110 vs 112) LSA (Lobe Seperation Angle), but less exhaust duration.

IVO = Intake Valve Opens
EVC = Exhaust Valve Closes
These two events determine overlap. IE: when both valves open.

Gwd, I hope I did my math right. LOL. It should be correct.

I was going by the rule of thumb that 112 lobe sep was the safe limit. I will refrain from mentioning a cam to anyone again.