455ci Engine Build Part 1- The Devil's In The Details

The oil restrictors were placed in the lifter bores on the intake side for a street application (the oil is a coolant for the exhaust valve). Holes were tapped and the restrictors were threaded in place.

The 6X cylinder heads had been previously ported to flow 230-cfm intake. For this build, they were ported to flow 255 cfm, and a high-quality, multi-angle valve job was performed. Intake-port velocity was strictly maintained at more than 300 fps. The Pontiac exhaust port flows well and wasn't touched. Unlike other engines, the Pontiac isn't exhaust-port deficient. Final flow values at 28 inches of water were 255-cfm/180-cfm, intake and exhaust, respectively. Both values were at 0.550-inch lift.

It's important to check the length of the cylinder-head bolts before installation. If the bolt is too long, it won't clamp the head gasket tightly and will result in premature failure-a common problem with Pontiac engines using aftermarket bolts.

Before the cylinder heads were installed, the block deck surface was cleaned with lacquer thinner and a lint-free rag.

JTES has a unique approach with intake-manifold fit. Jim Taylor and Mark Erney recognize that the water ports often cause the intake ports to misalign with aftermarket manifolds. To correct this, the intake manifold is cut to separate the water from the air side.

With the water removed from the air portion of the intake manifold, it was shifted for optimal front-to-back port alignment.

Using a vernier caliper, precise measurements were taken of the wall between the ports and were necessary to find the centerline of the port divider.

A great deal of attention was paid to the port match of the gasket.

The manifold was trial-fitted many times and located properly. Often it's necessary to mill the intake mounting surface to align the ports.

All engines are hot-run on a test stand before going to the dyno facility or being shipped to the customer for installation. The 455 is now complete and ready to be dyno tuned, which will be covered in Part II.

The manifold underwent a trial fit with a feeler gauge confirming contact with the gasket.

A stud girdle supplies support and limits deflection in the valvetrain. This is extra insurance that a posi-lock can't back off.