One of the most important parts of an engine assembly is the cylinder head. It holds the key to making power. It also offers the opportunity to make more horsepower. Cams, headers, carburetion can only go so far making horsepower without the cylinder head. However cylinder heads can be expensive but may be one place in the engine where spending the extra money may be worth it.

GENERAL BACKGROUND

We will leave most of the specific details on the cylinder heads, how to prep, etc. to the various engine chapters. Please refer to them earlier in this book. We will include cylinder head torque sequences and the various casting numbers for reference. In this chapter we will concentrate on photos and sketches showing various features of the heads.

6 CYLINDER ENGINE

All slant-six cylinder heads are interchangeable. There are no major differences between the various heads. The simplest way of identifying the various heads is by thehead casting number.

A. Casting Numbers

		Head
		Casting
Year		Number
---------------------------
'64-66		2206035
'67-74		2843169
'72-73		3614850
'72-74		3698995
'75-77		3698447
'78		3698447
'79-80		4104362
'81-82		4095778

Note: The '75 and newer heads no longer use spark plug tubes. It also uses the small "BL" series spark plugs and the tappets can't be removed with he head installed on the engine. The tappets can be removed with the head installed on the older engines.

B. Torque Sequence

The chrome alloy cast iron cylinder head (Figure 16-1) is held in place by 14 bolts. Spark plugs are located at the wide edge of the combustion chambers and aluminum spark plug tubes serve as spark plug gaskets. Install cylinder head bolts. Starting at top center, tighten all cylinder head bolts to 50 foot-pounds in sequence (Figure 16-2). Repeat the procedure, retightening all cylinder head bolts to 65 foot-pounds.

Comparing Figure 16-3 and Figure 16-4 the difference in spark plug arrangement can be seen.

The outside edges of the 6 cylinder head's combustion chamber is machined or relieved next to the two valves as shown in Figure 16-5. If oversized valves are installed these reliefs should be enlarged.

IV.

A. ENGINE

There are basically only two different cylinder heads that have been used on the "LA" engines from 1964 to 1984 a small port 273-318 and a big port 340-360. There have been only three different valve combinations in these heads: one for the 273 and 318 with 1.78" intake and 1.50" exhaust; one for the 1968-1971 340 with 2.02" intake and 1.60" exhaust; and one for the 360 and the 1972-1973 340 with 1.88" intake and 1.60" exhaust.

A. Casting Numbers

				Casting
Year		Engine		Number
-----------------------------------------------------
1964-1965	273		2465315
1966		273		2536178
1967		273/318		2658920
1968-1971	318		2843675
1968-1971	340		2531894
1970		340-6 MI. T/A	3418915
1971		360		3418915
1972		318		2843675
1972		340/360		3671587
1973-1974	318		2843675
1973-1974	340/360		3671587
1973		360 w/air pump	3671587
1975		318		3769973
1975		360		3769974
1976		318		3769973
1976		360		3671587-3769974
1977-1979	318		4027163-4027593
		360		4027596-4071051
1980		318		4027163-4027593
		360		4027596-4071051
1981-82		318-std		4027163-4027593
		318 H. P.	4027596-4071051

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