which heads to pick?
 

Im getting a 581 with Je flat top pistons my cam specs are:
[email protected]
Int. 258
Exh.262
Lift is .629 on both
Lobe sep. is 114
which heads would you guys pick? thanks.

I have heard good things about RHS. I just ordered two sets for my motors, so we will see, fingers crossed. Everything I read as far as build and dyno pulls shows dang good numbers, even compared to heads that cost waaay more.

What are your goals? Off the shelf or custom ported?

Looks like a Whipple cam.

my goals are whatever is cheapest with the most amount of power. I think the cam come from bob

Going with a blower ? What kind of power are you looking to make ? There is nothing cheap when you start building big inch motors .That said the cheapest part is the short block . just saying

fast, cheap, durable. choose any two. those inches though you need fairly big chambers. even N/A.

Brodix BB2 xtra CNC BP BB-2 X TRA
(CNC Ported) 2.300 Intake 183 235 294 340 376 395
1.880 Exhaust 134 177 216 247 268 280

Good blower cam but to much compression with flat top's for a blower . :poopoo:

its going N/A. Im not scared to spend the money but Im just like everyone else id like to find a deal
id like to see 750hp out of it

Please explain the benefit of big chambers for larger cubic inch engines? Another classic dereknkathy post.. :lolhit:

If it's a Madara cam, maybe you should consider giving him a call and see what he thinks.

calling bob is on my list of things to do. i was hoping to find a used set somewhere though

Might check racingjunk.com

i was thinking a cnc 345 brodix aluminum. what do you guys think of big iron heads?

:funnypost:

I've got three good used sets. Pm me if you're interested. They're a pretty average head with not a great cnc program but they work ok.

he always amazes me with his wisdom:lolhit:

i like the dart heads,a bit more money than the brodix,but u get what u pay for.

+1

how big of ones should i look for? and are the cnc's worth the money?

I've run both and have to disagree, never lost the guides due to poor workmanship on a set of Brodix.

Depends on the power you want to make,

If you call Bob he will most likely tell you AFR. I would recommend their 335's that are CNC'd, good flow and velocity. I have the 315's on my 524 with a slightly smaller cam. I haven't been able to really test the top end yet, but the acceleration is out of this world.

Agreed. Bob is designing my 578 right now. We are going with 335 cnc'd AFR's. Alum heads with good parts and a good port velocity. We are aiming for the 750 mark also spinning 5500-5700. Guy knows his stuff thats for sure!

You should probably talk to Bob Madera about the heads as if he has spec'd the cam he will know what head will be the best bang for the buck! Those camshaft numbers still kinda look like reversion to me on an N/A engine but if Bob says it will work , then It will work.

Next, want to build a good big power reliable big block 581inch -750HP marine engine, THEN DROP THE TERM CHEAP FROM YOUR VOCABULARY AND PRACTICES! A good marine 750HP reliable well constructed big block "AIN'T GONNA BE CHEAP" and you aint gonna find or build one on this planet! Try and you'll be back on this forum sometime in the near future whinning about the experience and problems. Not trying to be negative or critical here, just know that "Cheap' builds are just that! Don't build and buy your engine twice , its a costly and painful experience!

Best of luck on the project, hope you achieve great long lasting results!

Best Regards,
Ray @ Raylar

Im just like anyone else in this world i want the best deal possible. if i were cheap i woulda built my 454 to a 496 with a procharger that i still all own im my garage. im just looking for good true opinions from guys like arcticfriends and poker n run that have helped me out with there knowledge alot to this point.
As here in the prairie provinces in canada no one has any knowledge marine know how.
You will never see me in a competition as i live in nowhere land in canada. Im also not looking for a pusher on a product that they make the most commision on.
I was just in my small city at local race shops and there pushin me on edelbrocks. cause thats what they sell.
I just want some good ol truth from you crazy guys that GET summer year round. Remember i run a snowmobile from november till april too!
Its hard to keep all the #'s in my mind seperate as come november i forget all my boat knowledge and am running my sled.
Its hard to explain but i got 2ft of ice on the lake right now! I can always take a picture of the ice for you crazy BBC marine guys that never seen it, just ask.
And a BIG thanks to all the people that have helped me out with there knowledge I do respect everything you guys say!

Zeke,
There are a few simple tips to define the proper head for any application.
• Define realistic target performance parameters. Address the budget you are committed to and the collateral supporting components.

• Always select your induction path (carb/heads/ intake manifold/camshaft) to the scale of the engine. The scale is readily defined by a number of empirical data points. The displacement, volumetric efficiency, and RPM will define the necessary cross sectional area and delivery requirements.


Pitfalls to avoid.
• Flow numbers, used correctly, can be a useful tool in determining if the delivery will supply your targeted performance parameters, however they don’t supply the entire picture. They are a tool not an end. They can also be manipulated by test pressure and bore fixture size. Never use raw flow data as the sole criteria for determining head selection! It’s worth noting that exhaust numbers are often the most misrepresented/misused data point.
• Don’t get caught up in peak flow. Select a cylinder head that offers the best characteristics within the lift range you will be utilizing. There is no gain in selecting a cylinder head that flows 420+ CFM @ .800” for application exploiting a cam displacing .640” theoretical lift at the valve (closer to .600” actual after deflection and compliance). Keep you comparators within the useable range of valve motion. There is no upside to excessive CSA for the scale of the engine.You will find that will narrow your selection process.
Bob

I totally understand your special geographic situation and your limited boating season and obvious idea of the best bang for the buck thoughts.
I would say though with your very limited boating season window and remoteness for service work, tuning, tweaking and repairing, etc. I would recommend that you seriously consider purchasing a drop in "proven-ready to run" version of an engine and power you would like to have a possibly refrain from a do it yourself or local yokal type of engine build.
I am not looking for the job, but their are many good builders here on OSO who I am sure Bob at Marine Kinetics could recommend also who could give you that type of drop in-ready to run package and possibly save you some lost boating season trying to dial in a bigger horsepower marine engine.
Just my two cent opinion here.
Good Luck!

Best Regards,
Ray @ Raylar

That would of been the smart thing to do was buy a drop in. but then id miss all this fun! looks like there calling for a few inches of snow here on saturday so i have nothing but time.

Time is one part of the equation you can obviously fill, I hope you can fill the other side of the equation with knowledge and experience. Just make sure when the weather clears, the snow melts,the warm sun comes out and you're ready to rip across those waters, your boat is not tied up to the dock or on the trailer with poorly performing or broken engine!
Have fun, best of luck on your project!

Best Regards,
Ray @ Raylar

If no used set shows up anywhere in the next 2 weeks im thinking the afr 357cnc'd may be my pick.

I have been using the afr cnc heads for years on our engines work great,we use the 335cnc on 598 with hydraulic roller cam 9.5 compression right around 780hp 5600 installing a set in a 42 sonic as we speak

MDGperformance have you tried running anything bigger than 335's on the dyno?