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Spark Plugs & Spark Plug Wires (Group 2.240)

 

How to read an AC Delco spark plug nomenclature.

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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 Some of these may no longer be readily available or have been superseded by GM and can be used to cross-reference to another brand such as Autolite, Bosch, NGK, Champion, etc.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 (I65) 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.