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Spark Plugs & Spark Plug Wires (Group 2.240)

 

How to read an AC Delco spark plug nomenclature.

The following matrix of spark plugs used are for AC Delco as installed. Some of these may no longer be readily available or have been superseded by GM and can be used to cross-reference to another brand such as Autolite, Bosch, NGK, Champion, etc.

Year	Engine	AC Delco Spark Plug
1964	194/230	46N
	283/327	44/45
1965	194/230	46N
	283/327	44/45
	396	43N
1966	194/230	46N
	283/327	44/45
	396	43N
1967	194/230	46N
	283/327	44/45
	396	43N
1968	194/230	R46N
	307	R45S
	327	44
	396	43N/44N
1969	230/250	R46N
	307	R45S
	350	R44
	396	R43N *
1970	250	R46T
	307	R45
	350	R44
	396/402	R44T *
	454	R43T
1971	250	R46TS
	307/350 (L65)	R45TS
	350 (L48)/402	R44TS
	454 (LS5)	R43TS
1972	250	R46T
	All V8	R44T

* Early in 1970 the 3964290 cylinder head was recast to use the R44T tapered seat plugs so early castings may still use the R43N 'standard' plugs.

 

Spark Plug Wires

 

Not much to reading Chevelle spark plug wires. There are basically 3 different sets, one for I6 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

 

I6 Engines

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 I6 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.

 

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