It seems my torque curve could move up a bit if I used the Merlin Intake because the intake plenum is tapered down smaller then opens back up .

Intake Manifolds have been discussed many times on this forum.
The above statement from another recent thread inspired me to ask if that is true?
With the choices of intakes available, what are some of the attributes of the other single planes intakes?
What part of the design (ie. runner length, carb height, volume, etc) play in the performance of a single plane manifold?
As always, any reply is appreciated.
Russ

He must be talking about the plenum on the Dominator flange model. It curves back to reduce plenum volume. I alwys thought that would improve low end response, not high rpm.

Whatever you choose, the intake manifold, cam, heads and exhaust must work TOGETHER.

Get advice from engine builders before you buy these components.

They know what works together to give you the best end result.

Russ,
You can compute your optimum intake manifold runner cross sectional area by establishing your engine operating range and mechanical parameters. In your case you have a cylinder volume of 67.5 CI. If your target peak torque (max VE) number were 4400, for example, your intake cross sectional area would be 3.367 sq/in. for that displacement. If your runners are tapered you can average the cross section at the cylinder head flange, mid-runner, and the runner opening. Runner length will alter the placement of torque production on both sides of peak. The cross section is not the only factor involved in power placement. Plenum design and volume, cylinder head cross section, valve events, and exhaust are all factors. It's important that the pressure profile at the interface of the intake manifold to cylinder head remain constant to prevent separation at that point.
Bob

As always, Doctor Builder comes through with a dose of clarification.
But the question remains as to the differences between each manufacturer's individual pieces.
Is there data that shows the performance characteristics of each of these manifolds?
I am sure that not all single plane intakes are created equal.
Russ

Russ,
I am sure you know that I went through a tough decision making process about this same question. I wish that I could have had actual dyno time with different manifolds, but the truth is dyno time costs too much money for me to play around with. My h.p. and torque numbers ended up about where I was expecting them to be with the Dart oval port single plane matched ported to my rectangular port heads. I don't think I would have had much different results with other manifolds.

If anyone whats to e-mail me about this I will be more then happy to discuss it. When I was on a marine project with 540CID engines we dyno the Weiand, Victor Jr., Brodix, Dart, and GM Bowtie. All the manifolds did well, but yes there are some differences.

[email protected]

Chris

Can you post the differences??

Check,
Do to the fact we mfg many parts and sell to different companies in the performance aftermarket I can not politcally post this information. All of these manifolds will work and perform well, but each has its benefits to achieve certain power goals.

Chris

I don't know if this is still true due to the latest technology, but the old rule of thumb was: the dual-plane idled smoother and worked better on the bottom and mid-range and the single-plane was for top-end performance.
Still, the best results will come from the correct COMBINATION of cam, carb, intake and exhaust manifolds.
Do you guys agree?