View Full Version : SBC cylinder heads

Ted Guldemond
12-10-2000, 10:04 AM
Does anyone out there have any experience with aftermarket cylinder heads? I've been thinking of picking up a pair of World Products Sportsman II heads, but wonder if they're worth the added cost over say a pair of Vortec heads? Also, any experience with aluminum heads re: durability? This engine will be going into a St. Tropez (in saltwater with closed cooling).

12-10-2000, 08:50 PM
What size engine? What Rpm's do you plan on running?
I ran a Chevy 383ci with unported Sportsman II heads, the next year I wanted more speed. Looked into porting the heads but it wasn't much more to buy new ported heads. I sold the Sportsman heads and purchased AFR 190 CNC ported heads. The boat ran three mph faster with the AFR heads.
What I learned: The Sportsman Heads flow ok out of the box, when ported correctly can flow to make over 600hp.
The AFR CNC ported heads flow very well. With some room for an expert porter to play with.
Most of the pre assembled heads need an engine builder to go through them; to make sure the valves are up to the marine environments stress and that the valve springs match your cam specs.

12-10-2000, 10:14 PM
Hey GEOO- That 383, what's the meanest cam/carb(or EFI) combo you would recommend while keeping reasonable idle and drivability?

12-11-2000, 10:15 AM
As Geoo has alluded, it depends on the application. I chose WorldProducts cast iron S/R Torquer heads because the intake runner on the Sportsman heads is too large (no velocity) for a middle of the road stroker. I can't say what effect the heads themselves had since many mods were done at once.

12-11-2000, 08:09 PM
AAll this depends on your application. If you cruise between 2000 and 2800 rpms go with Paul if you go 3500 put on the big heads. World makes good stuff, there are better but the boat application it is a waste. With the right package big heads work. My corsican has a 351 Clevland big port heads 2.15 intake valves and 1.85 exchaust valves. It idles at 750-800 (not smooth as silk) will plane at 2200 cruises at 3200 to 4000 and will 5600+ rpms any time I want. This didn't happen overnight, it took a long time to get it exactually the way I wanted it.

[This message has been edited by BigGrizzly (edited 12-11-2000).]

12-12-2000, 12:39 AM
I'm doing a rebuild done on my SBC and we're going to follow the advice in Dennis Moore's book Small-Block Chevy Marine Performance. For my 86 Tempest 300 I've picked-up a set of 70's 441 heads. These will be upgraded with 2.02/1.60 valves and ported. I'm replacing the original Edelbrock intake with a pre-86 Chevy cast iron high rise dual-plane marine manifold. I picked up both of these items on ebay for less than $200 total. Overall these will not change this engine's performance dramatically but should make it more bulletproof. According to Moore, Both the S/R and Torquer S/R come in high compression and low compression types. Depending on which you go with there are alot of questions to answer about your overall setup. He says the 305 Torquer is for small blocks with a bore of less than 4.0 while the S/R and Torquer S/R are for small blocks with bore of over 4.0. Some of the more experienced mechanics on this site may give you better information than me. I'm taking this right out of the book. You can order this book on Amazon. It has a bunch of tips for pre 86, 87 and later, and the newer Vortec engines. It helped me figure out which way I wanted to go.

Good luck,


12-12-2000, 12:46 AM

More from the book..."The Sportsman II has very large 200cc intake ports and should be used only on the largest displacement, highest revving, and highest horsepower small-block marine engines. It has 2.02 intake and 1.60 exhaust valves, large 1.550 valve spring seats, a fast burn combustion chamber in either 64cc or 76cc sizes and a choice of either angled or straight spark plug holes". Moore goes on to say that aluminum heads are a bad choice for marine applications in general and a definite no-go in salt water.

Hope this helps.


12-12-2000, 08:09 AM
My 383 had a Hydraulic Roller Cam, Crane # 119631, in. 222,ex. 230, lift .509, .528. (this cam is a great all around cam) The engine had 9.5cr. The boat was propped to run 52-5400 rpm's. Good power, Good idle.
Had a strong smooth sounding idle.
If I was building a 383 again I would like to have the power band up higher. Crane's Cam # 119641 has IN 234, EX 242. lift .539, .558. I think this cam would move the power band up 3800-4600. The CR would move up to 10:1 (Alum. heads). The idle would be rougher.
If you have a small boat you won't need the low end power that a car or a larger boat needs. I would go with the bigger heads (200cc runners bigger valve's). The prop slips at slow speeds and before you know it the engine is up in the power band. My AFR 190 heads were ported to 202cc runners. This 383 pulled hard from 2500 to 4000. I Cruised at 4000.
My new engine is a lot larger (434ci) so I can run a bigger cam. It has a Loppy idle, (Sound's like a drag racer), but pulls strong from 3800 to 5200. IN.258, EX 264, lift .648, .667.. (This cam would not work on a smaller displacement.) I like the power band up higher for my type of driving. I cruise at 4000 and when I hit the throttle it pulls very hard. This engine's heads have 227cc runners, 10.2:1 CR.
The most important thing is to make sure all the components match. Bigger cam need more Comp. Ratio, larger heads, better flowing intake, better exhaust. Keep the air moving, Air in air out makes power. A big cam with low Comp Ratio will run badly. (Grizzly can explain better.) This my opinon, based on motors I ran in my 18 Donzi. I would talk to the cam guys and/or professional engine builders too gain more info. And ask yourself what type of boat do you want to end up with? A cruiser? A racer? ETC...

12-12-2000, 08:30 PM
Geoo, You have right. High compression heads make any engine easier to build. You can yse flat tops which make the fuel burning more complete thus more usable power. From here you can pich or have made a cam to fit your use. Just remember broad torque 2000 and up for allaround and skiing. The flatter the torque the more controlable the boat, and easier to prop. Most drives don't like rpms above 5800. Won't get into which drive is better, it just doesn't matter, they are all good if driven correctly.
Talked to Garry about your stuff last week he seems up for it. He seems to think your a good guy. I didn't spoil it for you. Talk to you soon

[This message has been edited by BigGrizzly (edited 12-12-2000).]

12-12-2000, 10:12 PM
Big G-,
Thanks, Garry seams like a good find!! However, I'm not sure I will go ahead with that project this winter. I think I may fine tune what I have and add to it next year??? GEOO

Ted Guldemond
12-13-2000, 09:07 AM
Thanx for all the great advice, I will definately pick up a copy of the book on marine engines. I should have included more details on the set up and application. My plan is to build a 350 with 4-bolt mains pre 85', cast crank reground and radiused, stock rods resized, beams polished, ARP bolts and balanced. Flat top hypereutectic pistons (9.5 to 1). For cams I was thinking about Comp Cams 12-236-3 (218/224@.050, .462/.477 lift 112degrees sep.)with 1.6/1 rockers. A quadrajet on top of a Weiand X-CELerator intake. Mercruiser exhaust manifolds to 4inch risers. The drive is a volvo 280. Again the boat is a 19 ft St. Tropez, mainly to be used in salt water (Massacusetts Bay, Ipswich Bay and Essex River) for wavejumping, fun and adrenalin. The family-ski Donzi is a 21 GT with a 351 W.

paul minx
12-13-2000, 10:36 PM
Invest your dinero in a strong bottom end and a supercharger.Any head w ports 200ccor above will be a waiste of $$$$$ on the kind of rpm your are going to be running..Healthy torque /hp at lower rpm = cubic inches(stroker) or supercharge .I don't care if you put a pair of Brodix /nascar or whatever a supercharged engine will produce more torque and horsepower at lower rpm.Prop up instead! When you have da torque you can move da big prop! Read the book it is there!

12-13-2000, 11:26 PM
Ted, I am going to open a can of worms. I don't like that cam, I tried it and sent it back, still waiting for my money, its only been several years. That was the weakest cam i used. Comp are good car guys but this is a boat. Go with Crane, Isky or Babe Erson cams. These guys know the need of torque at rpms above 3000 rpms. As for the small or big head theory, my Clevland blows that away. My 351 heads are bigger than a 454 head and I have great bottom end for skiing. A correct cam with that compression will work well. Don't expect 70 with that boat, but 60 is attainable. A blower won't fit under the engine cover. There use to be a light blue St Tropas in Mansquan NJ with that same set up, and it ran real hard.
Look at what Geoo said, he's been there. Like me he paid the dollars and learned the hard way. If it were me, I would go to 10:1 comp ratio. There are more cams amd head combinations available.

[This message has been edited by BigGrizzly (edited 12-13-2000).]