Spark Plug Wires
Not much to reading Chevelle spark plug wires. There are basically 3 different sets, one for L6 engines, one for small-block V8 engines and one for big-block V8 engines. All wires were manufactured by the Packard Electric Division of GM. The Packard 58404R wire was a TV and Radio suppression wire with a non-metallic conductor to reduce noise interference with electrical devices and has an approximate 4000 ohms resistance per linear foot. This suppression wire is different from the aftermarket version of the Packard "440" solid-core wire often used in racing at the time.
Spark plug wires were date coded according to the quarter and year
and this date coding was for internal quality control and may be significantly
earlier than the car they were installed on. There was generally quite
a lead time between 4 to 12 months from the date the wires were produced
and the time they reached the assembly line. A typical example would
be 2-Q-67 for 2nd quarter, 1967 meaning this wire may not get to an
engine on the assembly line until the 3rd or 4th quarter of production
and could easily be correct for 1968 models.
1st quarter - January, February, and March
2nd quarter - April, May, and June
3rd quarter - July, August, and September
4th quarter - October, November, and December
Both the spark plug and distributor terminal ends of the spark plug wire were straight, or 180°. The same is true of the ignition coil wire, both have straight ends.
283-307-327-350 V8 Engines
The spark plug end of the wire has a 90° terminal where the distributor end was 180°. The ignition coil wire has two straight ends.
396-402-427-454 V8 Engines
When the 396 V8 was introduced in 1965 a new type of wire was used with an improved insulation to better cope with the higher exhaust manifold and underhood temperatures since (except in 1965) there were no heat shields between the exhaust manifold and the spark plug itself. In addition to the new insulation, a new silicone spark plug terminal boot was introduced and is gray as opposed to black used on L6 and small-block V8s. All spark plug terminals were 135°with the exception of the #7 plug which received a 90° terminal due to clearance issues while the distributor terminals continued to use 180° terminals.