Mild-Mannered 440 Part Two

The Doctor studied each port with a velocity probe to "see" where theair is moving fast or slow, and where it may be hanging up or breakingaway. He commented that, "Indy needs to be congratulated on this piece,it's exceptional." Note the Max Wedge window outlined at the port exit,which comes cast at the standard 440 size.

Flow testing results exceeded our expectations, with an average runnerflow of 300.25 cfm as cast. We asked the Doctor for his overall opinionof this Indy manifold, and he responded, "I don't have an opinion, Ihave data and measurements, and this manifold proved to be one of thebest two-plane intakes I've ever tested."

The weakest port proved to be number 7 with a flow of 278 cfm. Probingrevealed some disruption right at the plenum, and as the port runnerturns out towards the exit.

The first step in our modification plan was to open the port exits toMax Wedge size, matching our head ports. The Doctor used a "dog-bone" toeye how the port narrows as it approaches the exit flange. These portswere clearly designed with an easy increase to the Max Wedge size inmind.

Similarly, the taper in the port height is gauged down the runner with adivider, allowing a quick reference of how the port height changes goinginto the runner. This helps determine how far down the runner to cut themanifold while opening it to the larger spec.

To quickly remove the metal, an aluminum porting carbide is used. Thelong tapered cutter shown here will be used for most of the heavy work.

The Doctor prefers to take a deep steady cut with the carbide, cuttingthe manifold like a human milling machine rather than the back-and-forthwiggling technique used by most amateurs. Note the first cutting passhas the manifold opened to nearly the final net shape.

Quite a bit of aluminum is carved away, taking the new size well intothe runner for a smooth transition. Just flaring out the exit at the endis almost useless.

A shorter, rounder, olive-shaped carbide is used to clean up the cornerradii. It pays to have the correct tools on hand.

The difference in port size between the standard port and the Max Wedgesize is readily apparent here. The port isn't taken quite out to fullsize with the carbide cutting, leaving some material for final finishingwith an abrasive flap. This takes the port out to final size, and nicelyblends the rough carbide-cut surface.

Retesting the intake after just the port match to Max Wedge size showedremarkable flow. average port flow was up 56 cfm, with the Indytwo-plane now handling a staggering average of 356 cfm!

Port number 7 was still lagging the others, recording 315 cfm (a gain of37 cfm), but not enough to make up the ground compared to the others.Probing the port with the velocity probe showed the same disruptionwhere the port curves out towards the exit that we noted earlier (shownhere), and an indication of separation at the top of the runner at theplenum.

To try and help the number 7 runner catch up to the rest, the turn outof the runner was blended, working it with the backside of a flap wheel.The plenum entrance was given a gentler radius (shown here), reworkingthe corner with the backside of a carbide cutter and then a flap wheel.It worked, with a gain of 33 cfm recorded for the effort. This work andthe port match added an amazing 70 cfm to this runner, bringing its flowin line with the others.

We had no idea how much capacity the Indy two-plane intake couldprovide, and were pretty shocked by how well it worked. With our finalflow numbers averaging 360 cfm, it will deliver all the flow our headscan handle. This manifold will be a key component in trying to achievethe outrageous goals we set for ourselves with this street 440 build.