The manufacturer’s manual provides detailed assembly instructions but includes little about the things that can go wrong. Most assembly errors can be categorized as follows:…
Category: Cylinder Heads
Top clearance, or the piston-to-head clearance at tdc, is critical. Unfortunately, the position of piston crown varies somewhat between cylinders because of the stacked tolerances…
Valve spring tension is all that keeps the valves from hitting the pistons. A “swallowed” valve is the mechanic’s equivalent of the great Lisbon earthquake…
Valve seat inserts are pressed into recesses machined into the head. (Some very early engines used spigoted inserts with mixed results.) Seats must be replaced…
Rocker-arm geometry generates a side force, tilting the valves outward and wearing away the upper and lower ends of the guides. The loss of a…
Aluminum heads usually carry the camshaft and are often mounted to a cast-iron block. The marriage is barely compatible. Aluminum has a thermal coefficient of…
Figure 7-25 illustrates a Detroit Diesel cylinder head, partially dressed out for pressure testing. At this point, most shops would introduce high-pressure water into the…
Assuming that both ends of the crack are visible, it is normally possible to salvage an iron head by gas welding. For best results, the…
Cylinder heads should be crack tested before and after resurfacing. The apparatus used for ferrous parts generates a powerful magnetic field that passes through the…
Minor surface flaws and moderate distortion can usually be corrected by resurfacing, or “milling.” However, there are limits to how much metal can be safely…