Hey All,

As the title says redoing top end in my 89 Scarab III with 454mags, 460hrs. Currently, the rig tops out at 54 at around 4500rpm. Cruises at around 35mph at 3600rpm. This is gps on speedview phone app so not too sure about accuracy. What I know for sure are my compression numbers:

Starboard: Port:
1 145 2 140 1 135 2 140
3 140 4 123 3 130 4 145
5 143 6 145 5 135 6 89
7 139 8 148 7 133 8 139

If all goes as plan I should have my wood gantry/hoist built this weekend and motors pulled by next weekend. I will be working with Marine Kinetics on the cam. My pockets aren't deep so I'm all over the net looking for those sweet deals and then researching to see if it will work. I was going to leave stock heads and redo valves and worn components but came across what I think is a good deal on some Brodix heads.

BB2 plus with the 312cc intake runner and 119cc chamber bare heads for $1170 a pair. I know this is another rect port head and it's not quite the most optimal on 454 but it's got to be better than my current heads, right? And, these can be milled to increase the static comp.

The other more optimal set are the Brodix Race Rite Ovals. I found these for $1000 a pair but they are Brodix's "overstock" heads with 127cc chambers.(they messed up when casting these and pushed the seats too far into the chamber). I called Brodix and they said the most these can be milled would be to 119cc.

I can go on and on about all this but would like to stop here for now and ask your opinion on these heads and what would be the best approach on THESE heads and my stockers. The performance gains I'm looking for is overall higher mph at cruising and WOT RPM's. I don't pull anyone with this boat just cruise, anchor and beach.

FYI, through the help of this site and a few others I found enough knowledge to assemble a work of art a few years back, a stroked 496 that dynoed at 555hp 6000rpm and 578tq at 4000rpm

Thank you all in advance for reading this long winded intro and for your consideration.

Jeysson

I will be upgrading my account so I can add pics to show the dyno from previous build and progress of current build. Wait till you see the hoist I'm building to pull the motors.

Straight to the point:

Will Brodix BB2 plus heads with rect port 312 intake runner be a good upgrade to a 454mag?

Personally with a build 600hp and below I've never understood why guys (not you) still think rectangle ports are superior. Plenty of dyno data shows that a good flowing oval to be a better choice up to around the 600hp level. And they will be much more responsive in a marine application. I went with Dart Pro 1 275cc alum heads which I'm having milled for more compression. With my combo it should be knocking on 600hp but in a 496 stroker. I would think your smaller motors would love a high flow oval ie AFR 265, DART 275....

I'm no expert, and I think you are wise to have bob M do the cam. Why not just run this by him. Even if the AFR heads are too much (he loves the AFR stuff), you can find deals on other oval port heads on eBay and such. If iron is a consideration, the DART 308 Iron Eagles might deserve some consideration. 1,000 per bare set on eBay. Kind of a oval/rect hybrid head. Less optimal than a true oval, but with higher velocity ports than the larger rect ports, and a .300 raised exhaust port.

Thanks for the info Borgie. I think I just found some bare Race Rites for the right price. Just waiting to hear back from BM on the oval or the rect port. Rect port is a 294 runner and oval a 270.

Heres a video of my buddy's Scarab III that had 454 Mags originally. TRS drives. I helped him do some engine mods. Boat runs mid 60's on GPS. http://www.youtube.com/watch?v=X7olqjFN8p8 Engines stock mag bottom Ends.
Stellings headers
Crane 134561 Flat Tappet cams
Roller Rockers
GM Rect port heads, stock 454 mag heads rebuilds on them.
Professional products Hurricane single plane intake manifolds
Holley 750CFM Double pumper
Stock Merc Ignition.

Boat has a very distinctive idle. He's very happy with the setup. He's turning 22p 4 blade Hydromotives to around 5300 I believe.

Take a look at this article. The cam really could be used in many marine apps from the look of its specs. But more importantly you will notice how easily they made close to 600hp with ovals. Put more cam in it and obviously 600+ is more than doable.


http://www.carcraft.com/techarticles...s/viewall.html

Yes, they are using a 496, but even a 468 with ovals would knock down some quite impressive numbers.

MILD THUNDER: That's a nice setup you posted as well! Very cool boat. I do have a question though. Why did he use a single plane intake? Seems like boats that run under 6,000 rpm would pretty much always do better with a RPM air gap. With the singles giving up quite a bit of low end torque and drive ability, and only benefiting a few hp up top. Just curious.

I would go with the stock rect port heads you already have and spend the money saved on top quality valves and an all roller valve train. For cam I run the 139011 crane in my 454s and have been very pleased.

Mainly for appearance. The hurricane intake is a copy of the dart HP500 intake. We weren't gonna be pulling skiers with it , so we didn't care if the engine gave up a little low end torque.

That article has some good info. Realistically , a 500 inch big block with 10.5:1 compression, should make those numbers with a good set of aftermarket heads. I'd like to see them test a 308 iron eagle against the other heads.

Ah I see! They actually did test the Dart 308 heads and they produced less hp. I need to locate the article. Before I bought my 275 oval pro 1's I spoke to a engineer at DART at length. He said that the 308 head are awesome but that the 275 outflow them and the aluminum composition obviously allows more compression to be run. That and the 275 head makes more torque sooner. I was seriously considering iron eagle 308's until I saw the dyno pulls and spoke directly to dart. Don't get me wrong the 308's are a definite step up from the 088's, but fall short of the PRO 1's.

Some folks won't accept the fact that oval ports are better under a certain HP. But results don't lie. The 088 rect port head is ok, and I agree it should be considered for a build that's restricted budget wise, but it's proven that the AFR 265 and DART 275 flat out spank this head into the gutter HP wise. Some folks don't like the fact that their big port heads are getting trounced by high velocity small ovals. To each their own I guess.

One thing to remember regarding the above article is that this 496 tested was using a pretty mild camshaft: 224/232 DUR/ 555/565 LFT 112lsa

Add a larger cam into the mix and the full potential of these heads will be seen!