A week's worth of work is seen once the carb is lifted off the intake. Simone altered the
Combining improper assembly with a weakened casting is a natural recipe for making the original O-ring gaskets fail, and it only made sense to fix these potential problems all at once. Miller personally oversees the production batch runs of the new heads as they are cast in Iowa at a top-notch foundry. The redesign of the head bolt supports, head gasket sealing, material, and heat treat make the heads a perfect match for those wanting to restify a '69 Mustang into a Boss clone. The heads as seen on their YouTube dyno video produce a bolt-on package good for over 700 horses with their "Classic" heads. For those wanting even more, TM also makes what they call their "430" version, with a high-efficiency combustion chamber and revised ports that flow over 430 cfm out of the box. The ShotgunHemiParts.com team used a set of those "430" heads as their starting point and continued with their induction system design.
The only aftermarket intake currently available for Boss heads (keep your eyes on the ShotgunHemiParts.com website) is the old Weiand PN 1990 tunnel ram. Simone was fairly happy with the base design of the intake, but wanted a different plenum for the top, so he looked around and scored a PN 1924 top plate for a big-block Chevy that bolted right up. The larger plenum worked better for the added cubic inches that the engine picked up. Even so, Simone claims to have 40 to 50 hours invested in making the plenum to the shape he desired, and introducing 1 degree of taper from the plenum opening to the cylinder head entry. Tailoring the length of the runners to the opening point of the plenum and adjusting the average diameter of the runners from the entry to the bowl area is a key design element in making power in a specifically targeted rpm range. Short runners tend to peak higher, and longer runners tend to favor a lower rpm range. Also, a greater amount of taper in the runner, say 4 or 5 degrees, would tend to be used in higher-rpm engines, where 0 to 1 degree of taper would do well with an engine built for more midrange power. Sitting between the top of the intake and the carbs is a pair of Magnaflow anti-reversion shear plates. Designed specifically for tunnel rams and sheet metal intake manifolds, the design of a shear plate keeps fuel from pooling on the underside of the plenum lid, improving the distribution and efficiency of the intake system.
The flat portion of the D-shaped runners gives more air a chance to go around a curve at t
Note how the end of the intake runner is filled with epoxy to match the entry at the cylin
The carbs in question are a pair of Dale Cubic-modified original Holley 4375 Dominators. The choke tower is a dead giveaway that these are period correct for the Boss engine. Cubic (of CFM Carburetors) suggested that the choke towers would help the air straighten out as it entered the boosters better than a newer style flat-top carb, improving the signal to the boosters down low on the big engine. Simone says his fuel curve reflected the theory as the engine was making way more than 600 lb-ft of torque at an earth-rattling 3,000 rpm.
Simone's day job at Diamond pistons allows him access to the latest innovations in piston technology, so when it came time to design the forgings (please don't call them slugs) for this build, he threw in every trick in the book, plus some. He started out with a full, round-skirt design, knowing that with the power he was shooting for, strength would count more than a lightweight design. He decided to become a guinea pig for a new skirt design by altering the ovality of the skirt. They took the traditional football-shaped design and made it more like two triangles back to back. Focusing the piston load on a narrower area of the skirt could lead to reduced friction, or a scuffed skirt after the first firing. A teardown after break-in confirmed the new design worked exactly as intended. The skirts looked perfect, and we can credit Simone with pushing the edges of the piston design envelope just a little further
Proudly made in the USA, the TM Enterprises heads can use either stock replacement rocker
CNC-machined, highly efficient combustion chambers are standard on these heads and were un