Look like the cam guy´s really know what they are doing..Is Bob Mandera from RMbuilder? must be the way to go...:ernaehrung004:

Help a dummy out here please...who or what is RM BUILDER??

Bob's screen name.

Thank you

On a 540 with any decent cam, cyl head, and carb I one million % disagree.

If you run a dual plane, even air gap rpm, then don't bother buying good cylinder heads. It will kill all the airflow the heads, cid's, and rpms would otherwise get and/or want.

Proven on flow bench, dyno, and the water for years.

One other thing, there are so many manifolds available that's it's really not good to assume they are the same. Example: A Sniper is not a Vic Jr, but both are single plane.

my 540 i used a 9.8 merlin block , canfield heads , crane 731 cam , 9/4/1/ total comp , merlin single plane intake ,950 holley hp carb, msd fire.

peak hp 560 at 5300 through stainless marine gen 2 exhaust with sea pump ,alternator..
tourqe was low 600's 3500 to 4300 rpm..

if i would have known more and consulted before buying parts , i should have went 565 with a bigger cam and a few other things , but the goal was 500hp at the prop..soo , i'm happy..

:ernaehrung004:
I agree as well.. If you read the original post though, he wants a 540 that makes 550hp @5000 rpm. In this particular application a small cammed, small runner head, dual plane combo would be a torque monster with wicked throttle response and peak in the early 5k range. If he wanted to spin it to 6000 or wanted another 150 to 200hp then bigger is better.

A 23' Velocity doesn't need a lot of low rpm torque to plane/accelerate.

Say if you only need 1/4 throttle to plane quickly why do you need more low end ? Your only using 1/4 of it. Even if 1/3 or 1/2 throttle your just using 1/3 or 1/2 of it anyway.

A 540cid in any configuration (tiny cam, dual plane, stock heads - big cam, single plane aftmk't heads) will make more than enough torque to plane/accelerate fast. Very fast.

Yes, with stock heads a Air Gap RPM won't really step on it's airflow much.

An aftmk't rotating assembly (other than Scat cast crank) will live at 6k or more no problem. Hyd / Hyd Roller Valvetrain may have harder time. Exactly 5k is a little low to make real good power, but each 200rpm step (5200,5400,5600) will bring much more power to the table with no loss in reliability.

A 540cid with aftmkt heads (or well ported OE rect's) and well chosen cam will make more or same power at 3000-3500 with single(Vic Jr/454R) vs air gap rpm, and then around 3500 it will start pulling away. Yeh, that low ! This is no OEM rect port, low comp, hyd cam 454 .

It is what it is, therefore I'm just stating what it is. No theory here. Just real stuff.

I agree with Jeff and some of the others. I also would lean towards a good single plane intake manifold vs a dual plane.

The Dart single plane is a good choice. Plus many are around used. Brodix or Victor may be too big. In the original post fbh said he wanted to use his 990 GM heads. For the power levels he's looking at, aftermarket heads are a huge waste of money. Use a fairly large cam with a long duration exhaust lobe to crutch the poor flowing stock exhaust port and you're all set. That;s what the 741 was designed for. I think the 731 wil struggle to make 550 hp in this instance. It's a good 454 cam but it's pretty mild even in a 502.