all 454MAG Created = ?
 

Dear Board Mercruiser Guru's:D :

I have a 1990 454Mag (per Serial #).
Decided I should ID cam.
Appears to be a stock GM Marine cam #14096209. A 300 hp cam :confused: ? (not what it had been represented as to me).
It does seem to have rectangular port heads though Casting # 1409**8 (**=numbers bloted out by coffee stains on note book- will get again).

Question: Are all 454MAGS created equal?
I would like to throw a better cam and intake on this unit (it is in great shape) but am leary that the heads and or bottom end might limit success.

Can anyone tell me what is different between a 300hp (apparently what I have) and the 425hp MAGs and can I get there from here without different heads? Can't seem to find anyone local who knows.
Thanx for the Help,
Confused in Indiana......

To my knowledge the carbed 454mag was a 365hp motor. Not sure where you are getting the 425hp figure from??

The way to tell if it is a mag motor is to check out the heads....They WILL be Rectangular Ports. If you don't want to pull the intake, pull a valve cover....it shoulf say "HI-PERF" in the casting.
If they are oval ports, then you have a base 330hp...or under...(300hp or 310hp) motor....in which the bottom end is made of cast components.

I have heads off. They do have "High-Perf" cast onto them.
454 Mag-365hp was what I was told the motor was, but this
cam number has me a little concerned.
Was thinking of putting the stock Merc (neh Crane) 425hp cam into it with a different intake. Wanted to try and confirm what I had first though.
:)

Check again....
 

Hey Ernie,
the 14096209 is the stock Mag (365hp) hydraulic cam.
It's listed as 224/224 .510/.510 and is used w/rectangular ports, forged pistons, forged crank, etc.....
You could do much better however.
Dave
:)

Thanx for the imput, I feel much better now.
Any opinions on the 425hp Merc Cam Grind?
228/236 and 0.530/0.551
Or is there a favorite for mild-warm overs?
(Only thru-hull currently for exhaust).

"it shoulf say "HI-PERF" in the casting. "

actually many oval and small oval (peanut) port heads are also marked hi-perf specifically for example casting #'s 14081052 and 14092359 from the latet 80's, These were generally truck heads but used by merc on many of the 330's

you have to look up the casting number, HI-PERF means nada

:confused: Where does one look to find Casting P/n Reference?
(the questions continue):confused:

www.mortec.com is where I go to check GM numbers.

If you have the heads off....., then Screw the casting numbers. Are the ports (intake side) square OR round??

The ports will tell you!.....unless someone (previous owner) put Mag heads on a non Mag motor....but i doubt it...nordicheat says the cam #'s are from the mag motor.

you shouldn't have anything to worry about.

for older gen V and mk IV engines like yours try http://www.mortec.com/bbc.htm

good info on location and block markings there to

THANX FOR THE INFO:D
COOL SITE...

I just finished up 365 mag
 

I had bought 365 Mag rectangle port heads all 365 hp have rect heads. This was off a 1991 boat. Heads, block oil pan Steel crank.

1. Sent heads out for valve job, did not replace valves,had them dipped new seals cleaned up, heads decked .030

2.Crane Cam 286/296 .05 112 Flat Tapped matched springs
Gold Series Roller Rockers

3. Bought 500 hp valve covers grind the tips out, Its a must

4.Elderbrock RPM Air Gap.

5.850 Holley

Dynoed 470 flbs@ 3500 420hp @5000
This set-up brought on 400 flbs at 2500 and 439flbs @5000
and didnt miss a beat.

I tried many different carbs and a Victor Jr intake but the Air Gap was the best set-up with the 850

Hope this information helps

I got alot of parts from Jegs and Summit. I also used alot of parts from my totally wasted 330.

When it was all said and done I spent $5,200 that included the Dyno testing, the take out and put back and Misc.

Everyone says they could have done it for a whole lot less!!!!!

This was my first motor.

Good Luck with everthing.

Nobudget

Sweet. Thanx for the info!
You are the 3rd person today to bring up the RPM intake as a good choice. Think I'll make it mine too:D

I know this isn't a test, by why I'm at the well-o-experience:cool: :

- Any guesses as to what the 0.030 deck bought you in terms of static compression ratio?
- Any idea how far you can go, deck wise, before hitting the never- popular but always-present "practical considerations"?.

Not sure what the increase in .030 decking would be, but I am about to test an assumption on rect port heads vs oval port. I had fancy rect port al edelbrock heads on my 365hp mags. Nothing but trouble... and nearly out run by a single 330hp baha 240. I am in the process of changing to oval port cast iron heads with edelbrock performer intakes. OSO generally says rect ports can't support the low rpm (5k) of boats and that oval are better. I am going to find out. The rect ports don't start working until 6.5k rpm and I will never be there with my boat. I am thinking oval ports are the chit with a boat and gonna find out. I"ll let you know what happens. 330s come with ovals.

BT :cool:

Just a point of clarity. 330's come with peanut port oval heads (truck heads) that make good low end torque but run out of capacity over .500 lift (except for the late model vortec heads). The good oval ports are the early Gm heads (cast number 049 or 781) that have large oval ports. They will do better than the rectangular ports in the 5000 rpm and less range with large valves( 1.88 and 2.19). However, Jim V has made some good numbers massaging the peanut port heads. I run torker 2 intakes due to deck clearance problems. I agree the airgaps are better if you have the room.
Tom

Milling the heads .030 will increase static compression from the stock 8.75 to real close to 9.0 and .030 is about as far as you can go on the heads before having to modify the intake according to my machine shop.

i have a pair of large oval port heads sitting in my garage :D
They came off my 1987 454 "mag" basicallya bone stock 330 7.4. unless the large oval port heads were what made them a "mag" didn; seem to make any HP difference though...

Formula31 is correct. Go to the large ovals with the 2.19 intakes and 1.88 exhausts. I did make 422 HP last year with peanut port heads, but they had the large valves in them. Low end and midrange was great, but it would run out or steam around 4800 RPM. I went to the large ovals this year, but I am not in the water yet. Also, don't worry about the cast crank. It's good to about 500 HP. Have it line bored, make sure everything is straight and it will be fine.