looking for some input on ready for some mods!!
 

I'm look for some Idea's I'v got a 454 mag 365hp and thinking of putting on some upgrades ,like a BIGGER solid flat tapit cam ,merlin rectangle port heads ,dart oval port intake and 830 or 850 holley carb ,STOCK BOTTOM END. would like some ideas or recommdations. THANKS

:confused:

mods for a 454 mag
 

I did just the type of thing your looking for over the last winter.
I went with Edelbrocks new aluminum rect-port heads, Cranes hydraulic roller cam w/ 228 intake, 234 exhaust @ 50 duration w/
587 and 610 on the exhaust side. I also used cranes gold race rockers, full msd ignition, holley 830 cfm mechanical secondary race carb on a edelbrock performer RPM intake and gil exhaust.
I had my engine run on the dyno and it posted peak numbers of 467hp at 5300 rpm and 523 ft/lb at 4100.

Do some more research.I would run large oval ports as you will get more torque. If you will not be turning over 5500 then you don't need rectangle ports.

Check out this thread LOTS of GREAT info here on this board. Read listen and learn. There is a lot of good expierance here and most are willing to share there hard earned knowledge. You do have to sort thru some of the #$%^s sometimes. Good luck.

http://www.offshoreonly.com/forum/sh...threadid=31011

Have Jim V. put wedges in your stock heads and set you up with the right combo and it will really fly. His shop is in Grand Rapids MI

Best advice, get Dennis Moores book on building marine big blocks. Read it thoroughly and then build a plan on what you want to build for a motor. Knowledge is power and isn't that what your looking for? The info in the book will help keep you from making a lot of commonly made mistakes, like solid cams. A hydraulic roller will make better power with less maint. Aluminum heads and salt water don't mix, not necassary if your running less than 10.5:1 comp., and alot more money. Oval port vs. rect. port heads; rect. port heads were designed for drag racing motors and make best power in rpm ranges too high for average boat motor. yes they come on motors from merc., because they come on motors from gm, because gm standardize on the rect. port heads when the large ovals were no longer being made, not because the rect. port heads were better for boats. Example, engine builder friend who has dyno in shop builds two equally radical motors, #1 is a 509, #2 is a 540. #1 uses ported 290cc merlin oval ports, #2 used ported rect. ports. The 540 only made about 20hp more power than 509. 540 also made more torque, but then it should have, 31 more cubes. Engine builders opinion, oval port heads are greatly under appreciated and utilized.
Get the book, save money , make better power.
Holland, as in Europe?

Dyno and SuperV are running Merlin oval-port heads with mild hydraulic flat-tappet cams. SuperV's dyno'd at 505 hp. Both boats have been very reliable. Contact Dyno for further info.

Yea same here. I run the early GM large oval ports and they work well with large valves. If I had the money, it would be oval port merlins. My personal opinion is the 850 carb is too big for a 454. I use 780's and they started and idled better, with better fuel usage than the 850. Top end was the same.

Put a 250 on it. Keep the boost to 4 or 5 lbs. Keep the stock cam, pistons, and bottom end but use a big 4150 carb-NOT a dominator. Retard the timing to about 24* and you should be over 500hp. About the cheapest/easiest way to get alot of power out of that engine.

The problem with the oval port heads is the tight radius into the valve opening and into the cylinder. With oval port heads the port is at the bottom of the head. What Jim Valakeo does is put wedges in the bottom of the rect. port heads. This raises the floor of the port about 1/2 inch and greatly increases the radius of the port to cylinder turn. He also put 2.3 intake valves in my heads (509 cubes). These engines ARE NOT SLOW and have more torque down low than I need to get on plane.

you are still dealing with a 454, and dealing with limited torque. to make more speed you need torque, that only comes with cubic inches and stroke to make torque, or supercharging. all the cylinder head work by who everever will not gain you very much speed, unless you increase those things.

How about at least 15 MPH-- that is what I gained with my 251 CHECKMATE after the engine build up.


How about 638 HP from a 454. Is that enough for YOU. Stock bottom end, Stock compression, Dart heads Reworked and wedges installed by Jim Valakeo, Dart intake and 850 Holley,Ultradyne roller cam.

Thanks alot guys for the info I will start making some phone calls.

Some good advice!
 

Man you guys are good! Thanks for the kind words about my book!
Sincerely
Dennis Moore

I did go out and get your book, time for more research.

Hi Buddy,

Better get your checkbook out, too!:D

Doug :cool:

Re: Some good advice!
 

i i would like to buy one of these books i have heard good things about it. how do i get one ?

you can go to amazon.com or your local book store and ask for BIG BLOCK MARINE PERFORMANCE by DENNIS MOORE.

Tinkerboater, what cam did you use in that 454 to get 638 HP? I am currently helping a friend with his 454 MAG and could use the info. That is some good HP out of a low compression 454. I probably only make a few more than that with my 13:1 compression 496 with fully ported pro1's and a solid roller!! Nice job!!! Please share the cam specs. Thanks, Craig

Years ago, my friend put Merlin rectangle ports on his 454 Mag and used a Crower flat tappet cam. It would run a solid 75-78mph in a 251 Convincer with the AME4000 hull.. a bit lighter than mine. It ran forever with little maintance and it always ran strong.. I have the specs around somewhere... I think it was a Crower 1209 if my memory serves me.. which it usually doesnt..

Dick

I no longer have the card for the cam-- hey it was 8 years ago but Jim V. can probably set you up with the right cam.The main problem with the rec. port heads is that the port is to big and it slows down the incoming air flow ( no ram effect ) The oval ports have about the right size port but the angle of entry is poor. So You raise the floor of the rec. port heads about 1/2 inch thus making the port smaller (oval port) to increase the velocity but it also has a much better entry radius into the cylinder so get the best of both heads. You also have to raise the floor of the intake manifold ports 1/2 inch. The cam I ran was a big ( for a 454 ) sollid roller. T he 251 Convincer went from 68 mph to about 83 mph.

Sounds like a cool trick and it makes sense. Where are the limits for wedged heads as opposed to stock or mildly proted heads w/o wedges? (cu. in, rpm, etc..) Can the wedges later be removed and how much does it cost? What type of intake needs to be used? Just seeing if it makes more sense to get new heads, get wedges, or bore/stroke the motor for more cubes so the stock heads will work better. Thanks for your input.

I have a set of the Jim V heads (merlins with wedges) on my 468 in a 251 convinsor and all I can say is ALWSOME.:D :D :D Low 80's. It does have a solid flat tappet cam. I bought the motor from a freind of Mr Gadgets, Dick his brother is from KOOl. Is that the motor you were talking about ? If so I have the cam card. Also I was running a 930 holley (carb shop mod 4150) it made great power but had a huge bog. Now I am trying a 870, still jetting, but well see.

Craig/Wette Vette,

JimV told me that my Dart Pro-1 310cc heads were too small for his wedges but he told me that for a 540 cubic inch engine that I would NOT need the wedges----mine flow well enough without them. They might work in your 325's though.

Convincor 251,

I would suggest a large oval port head as some have already suggested---especially for a 454. HOWEVER, being that your 454 already has the stock GM rectangle port heads then wedge inserts from JimV's shop would be a KILLER improvement. That way you wouldn't have to go buy a set of new heads.

I have a 454 very similar to f252tbird's, but with oval port heads.

I already had the Edelbrock aluminum oval port heads, Edelbrock RPM dual plane intake manifold and MSD ignition when I asked Tyler Crockett to help me with my engine upgrade. My engine started as the basic 7.4L carb engine, and Tyler upgraded the crank, rods and piston to forged.

This was the third engine he has done for me, and each has been built for conservative and reliable horsepower at around one horsepower per cubic inch of engine displacement, and tuned to run on the 87-89 octane gas I am able to buy on the water.

Tyler upgraded the valves in the heads to 2.25"severe duty stainless intake and 1.88"inconel exhaust. The cam is a Cam Motion hydraulic roller cam 227/235 duration @ .050, .594/.609 lift, Crane roller rockers, Gary Williams modified 750 Holley double pumper, and CMI elbow top exhaust. Compression is 9.1 to 1 and total timing is 34 degrees. The engine dyno'd 464 HP at 5400 rpm and 507 ft/lbs. of torque at 4100 rpm. The engine gave me a flawless summer of fun with great out of the hole torque and impressive midrange to full throttle acceleration.

I too have worn Dennis Moore's book out the last two years! Thanks for participating with us amateurs!