Intake Inserts

INS-351C 4-V — 351 Cleveland 4-V

The 351C 4-V heads put out serious CFMs, but low-end torque has always been a challenge for circle track racers and street rodders. By installing the inserts, airflow and velocity improve so much that even drag racers have been impressed.

The air likes to run down the top of the port — so why not block off the part that isn’t working and increase low-end torque at the same time? The idea of filling the bottom of the intake ports goes back to when Bob Glidden was drag racing.

The castings are glued into position with Miller-Stephenson glue and left to sit overnight. Then drill, tap, and insert a button head bolt from the bottom side of the intake runner. Use 2 C-clamps per port for the best fit — careful installation means blending with a 3/8″ sanding roll takes about 5 minutes per port.

🔧 Pair with: AP-35W Intake Adapter — run 351C 4V heads on a Windsor block.

INS-429SCJ — 429 Super Cobra Jet

The 429 SCJ heads are used in a variety of ways. Not all customers need a port this large — the valves are big, but the oversized port can hurt torque.

These 8 aluminum inserts are pretty much to size, so when you install them there’s no need to mill off material. Use 2 C-clamps per port — one at the front edge and one in the back. The short side radius in the back is always the hardest area to work with a sanding roll, but careful installation with C-clamps means you can tweak it out with a 3/8″ sanding roll in very little time.

Directing the flow in the intake port is one of the better horsepower-producing ideas to come along. Put it where you want it and enjoy the results.

INS-BBC — Big Block Chevrolet

You just got to love those Big Block Chevy heads. Now that you have them, you’re thinking — is there any way to improve them?

Porters know what we all know: the air wants to run down the top of the port, making the bottom less important. Reducing the size of the intake runner increases velocity and really improves performance at the track and on the street.