GMPP Gen VI 502 Engine Build - Plan B

Forgoing a conventional timing chain, Jason opted for a Jesel beltdrive system. With numerous dyno runs in store for the 557, he wanted something that was user friendly and easy to adjust on the fly.

The oiling system features a Stef’s standard volume oil pump and Stef’s aluminum oil pan. The lightweight pan uses a baffle and trapdoor setup to keep the 557’s oil under control.

Jason turned to Trick Flow Specialties for a set of PowerPort 360 cylinder heads. While the heads flow well right out of the box, he couldn’t resist putting his own stamp on the castings. In their off-the-shelf form, the heads have 360cc intake runners and deliver an impressive 365 cfm of airflow.

Using a bridge dial indicator, Jason found that the pistons protruded from the bore by 0.005 inch, effectively lowering the deck clearance and increasing compression. Since he was shooting for 0.046 inch of deck clearance, Jason ordered a set of 0.051-inch-thick Cometic MLS gaskets to increase the deck clearance to his liking; the result is a 9.6:1 compression ratio.

Using his years of experience with top-end engine components, Jason did his own port work on the heads. He started by welding material on the intake runner floors, essentially raising the runners by 0.150 inch. He left the cross-sectional areas alone, but changed the intake valve angle from 45 to 50 degrees. Once he was finished, the intake runners were still 360 cc, but airflow was increased from 365 to over 400 cfm. The good news is you can expect Trick Flow to carry Jason’s version of the PowerPort 360 heads in the near future.

For increased valvetrain stability, the rocker arms were welded together—a trick the team uses on its Pro Stock engines.

Trick Flow’s R-Series intake features a single-plane design for 500-plus cubic-inch engines, making it perfect for the 557. Jason sent the manifold to Wilson Manifolds, where it was massaged and port-matched to the custom runners he created for the Trick Flow heads.

The Trick Flow intake works with Holley Dominator–style carburetors. Jason’s carb was outfitted with a set of Willy’s Carburetor and Dyno Shop metering blocks and bolted onto a Wilson Manifolds spacer to enhance airflow and air velocity.

Thanks to this 812hp Pro Stock–inspired 557, Jason’s 4,500-pound Biscayne wagon will have no trouble getting the Line family to the grocery store in a hurry! CHP