BUICK SPARKPLUGS 1929 -1942 DELCO AC

[mlander]

PRE-WAR GENERAL AC SPARKPLUG CHART 1929-1942 ONLY.

1929-30???????...??..88 (18mm)

1931 thru 1937?????.??84 (18mm)

1938-39-40-41-42?...??.......46 (14mm)

This an expanded list of just the 18mm sparkplugs only.

18mm by ½? reach

CHAMPION

D6

D9

D14

D16

D18* SEE BELOW

D21

D23

D15Y POWER TIP

D18Y POWER TIP

DELCO AC

C81

C82

C83

C85

C86

C87

C88

C85S POWER TIP

C86S POWER TIP

AUTOLITE

373

386 RESISTOR

388 RESISTOR

3116 POWER TIP

Because a sparkplug number is listed on this sheet does not necessarily mean it is easily available from the various AC, Autolite or Champion dealers. At the rate that these plugs are being removed from manufacturer?s charts many sparkplugs will no longer be available, from any dealer shelves in even the near future. This seems to be particularly true of AC.

Note that in many Buicks of the years from about 1939 to around 1942

were engineered with 10mm sparkplugs which were less than satisfactory

in actual service. Many cylinder heads were remachined to use 14 mm

with the 10 mm sparkplug insulator bodies which allowed more gap

between the insulator body and the sparkplugs outer shell.

M.L. ANDERSON

[Fred Rawling]

The numbering system for AC plugs was changed in 1937.

The pre 37 number for # 88 is G 14,

for 84 the pre 1937 number is G7

for 46 the pre 1937 number is K9

[mlander]

BUICK 1929-1930 DELCO AC # 88 replaced the J-12 & G14

BUICK 1931-1937 DELCO AC # 86 replaced the J-9,J-12 & H-9

These sparkplugs were later changed to C88 and C86 which are available today.

The above does not give any differentiation between the low compression and the high compression engines. This is very likely due to the fact that AC engineers found that sparkplugs had a much wider heat range per sparkplug than thought possible in the very early 1930?s! My 1932 BUICK Shop Manual states that the J-12 was for Low Compression and the H-9 was for High Compression engines. Do not confuse the J-12 and the H-9 with Champion plugs as they; J12 & H9s are the early version of the C series of the Delco AC 18mm by ½? reach sparkplugs. The only difference I could find was the arrangement of the ground electrode. This was sitting off to one side instead of directly above the center electrode. At least this is true of the 1932 BUICK shop manual page 122 Figure 188.

M. L. Anderson