I have 454 mags 365 hp from 1988 that are original to the boat. They are at around 1000 hours on them. I know it is getting time to do some work on them, so I am looking for some info.

What would you all reccomend to get for these motors? Also what could I do to get a bit more power out of them? I am not looking for huge gains. I spin 23p labbed props at about 5100 RPM at about 68 GPS. I got a set of 24P four blades that make the boat ride great, but I can only spin them a about 4400 RPM and 64 GPS. I would like to be able to spin these props at 5100 to 5300, touch 70 and I would be happy.

Just some part numbers would be good. I want to buy the parts here and there as I have the cash. I have someone that can do the work.

Any help would be great.

I don't have part numbers on hand however I'll give you what I know works well and would help you obtain your goal.

Dart oval port heads
Air Gap intake
Comp m278 cam
Holley 9022-800cfm carb
1.72 Roller Rockers
9.5 to 1 Comp.
Gils or Emi Exhaust.

Not sure if this what your looking for or the amount of money your looking to spend however this would put you near 500 hp.

There are several different routes you could go however this is just an option and a proven package. The other cam that works well with the combo is 502/465hp cam however that may cause reversion depending on what exhaust/risers you use. Parts new may get a little pricey however you can always search out used for some of the items such as heads. There are 2 sets of Edelbrock oval ports thta were on the swap shop the other day. I strongly feel with a 454 build that having good flowing heads and bumping your comp is huge.

I have a dyno sheet on the above combo if your interested also. Dart oval ports were used on the said engines.

Good luck,
John

John,
Is that comp cam a roller? I guess you also decked the block/changed pistons? I have low hour mags and am looking to up the power without pulling the motors and disassembling the shortblock if possible. I am also curious to see your dyno sheet.

It's been a while since I had a mag apart however if I recall they have a forged .090-.120 dome on them. When I did these builds I did it on a 330 foundation however I swaped the pistons out with what I think were 365 mag pistons. They had a real low dome as state above. I also had the heads decked to achieve the comp ratio however it seems liked I advanced the cam 4 degrees also so I was getting a little close with int valve to piston clearance. I did do it though without having the pistons flycut. The cams I used were flat tappet hyd. If you wanted to go hyd roller you'd make more power. With that said I would use the 731 cam or call Bob. Run the 731 straight up. Roller set up adds about 800.00 per engine.

That comp cam is not a roller. Go to comps site and check it out. You can even listen to it. LOL...

John, I would like to see the dyno sheet on this combo as another possible option. Thanks, Wayne

if you want to keep your bottom end together
you need to take a good measurement of how far your piston sits in the cylinder to get an accurate measurement of your compression
that being said
look to shoot somewhere between 9.0-9.5 to 1 compression if you want to use iron heads and regular pump gas

I just did a motor with 9.25 compression,
stock magnum forged bottom end pistons, and 502 steel crank, with a set of Eagle I beam rods (cause I got a good deal on them) but could use the stock magnum rods as well,

large oval port cylinder heads, fitted with 2.19, 1.88 Severe duty valves
a good amount of port work done to them

custom hyd roller cam from Bob Madera (Marine Kinetics)
Morel hyd roller lifter,
trend pushrolds
Lunati roller rockers
air gap intake
850 cfm demon carb double pumper

motor should make at least 500 hp at 5000 rpm

When I did mine I took the motor out and had the block zero decked and boiled and put all new bearings in it,
and had the bottom end balanced and added a new flywheel and balancer
but you do not have to do this if your bottom end is in good shape and gets good oil pressure etc.

look for a set of early casting large oval port heads and have them milled to get the compression where you want it to be

I recommend going with a custom hyd roller cam
and go with Morel or Crane hyd roller lifters (not any other brand)
this combo will get you to 500hp and run great all day long,
just remember to use a quality set of exhaust manifolds,
Emi, stainless marine, etc.

To gain 700-900rpms, you are going to need about another 125hp. What drives do have???? Are you sure they are the 365hp 454mags???? I think a lot of the early 454mags were actually 330hp. What are the casting numbers on the heads???
You are going need to invest 10-12k to get close to your goal.

454 Mags have pretty good parts in them, should have decent Aluminum Intake, Decent heads, good crank and rods. If the economy turns around and I get into mine. I was going to have the heads re-worked by Crocket engines (Pure Michigan), full roller cam, good exhaust, new cam (you gonna have to pick your own cam, everybody has a favorite). Bump the CR by pistons, or decking & shaving. Might upgrade intake & carb but would have to see if it was hurting me before I dropped the money, or just copy the 525SC version with a little more cam seems to be a pretty sweet combo also.

Do your homework and build it your way, it is your money that you worked for spend it accordingly.

Jim