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Budget Rebuilding Cylinder Heads

Performance Is All About Airflow, So Let's Dive Into . . .

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Rebuilding Cylinder Heads - Why? Car crafting is all about power-enough to run 12s in the quarter-mile and spin the tires at will. But not everybody can afford a shiny new set of aftermarket aluminum cylinder heads. The next best thing if you can't afford a trick set of alloy castings is to lay a little TLC on the heads you have. Last month, we introduced you to Steve Strope and his stepson Seth's '66 Mopar Coronet. While the resurrection bodywork continues on that somewhat abused B-Body, the pair also opened up the 318 Mopar engine that will eventually find its way into the engine compartment. The Coronet's original powerplant was an ancient polyspherical 318 that only the most diehard Mopar fan could learn to love. Instead, the pair chose a '70 LA version that promised to be in better shape. At first, the Strope plan was to perform a quickie Krylon rebuild by just cleaning and painting the low-mileage donor motor while adding an intake and a cam. That's when the, "Well, as long as we've got it apart" song started. Before the final note had played out, the heads fell off in anticipation of a quick valve job. We took the heads to Jim Grubbs Motorsports where ace machinist Ryan Peart transformed the greasy leakers into like-new castings.

Most guys don't have machine shops in their garages, so the focus of this exercise is to point out areas where a couple of simple and inexpensive machining steps can improve airflow for cheap and to illustrate just what goes into a quality rebuild on even stock iron cylinder heads. Check it out.

Guide to Rebuilding Cylinder Heads
The biggest issue with rebuilding cylinder heads is valve stem and guide wear. Generally, used heads will have loose guides that allow the valves to move laterally relative to the valve seat. This movement tends to beat up the seats, deteriorating their condition, which also diminishes the seal under cylinder pressure. If this isn't bad enough, loose guides allow the valves more room to move around, which trashes the valveguide seals. From this short description, it should be clear that a set of properly installed and clearanced valveguides is essential in the build process. So that's where we will start.

Rebuilding Cylinder Heads: Valve Grinding

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