Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1986C 10 P/U 2WD V8-350 5.7LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTIGNITION SYSTEMTECHNICAL SERVICE BULLETINSBY SYMPTOMDRIVEABILITYSPARK PLUG - REVISED APPLICATION CHART
1986 Chevrolet C 10 P/U 2WD V8-350 5.7L
Spark Plug - Revised Application Chart
1986 Chevrolet C 10 P/U 2WD V8-350 5.7LSECTION Spark Plug - Revised Application Chart
86chevy10
Number: 86-137
Section: 6D
Date: AUG., 1986
Subject: SPARK PLUG USAGE
Model and Year: 1986 LIGHT DUTY VEHICLES WITH GAS ENGINES
TO: ALL CHEVROLET DEALERS
The following information is being provided to assist dealers in the correct spark plug usage in 1986 Light Duty Trucks. Starting in 1986 many spark plug usages were changed. If it becomes necessary to replace the spark plugs, use the chart below for the correct plug application. It is not recommended that higher heat range plugs (example R43CTS to R44CTS) be substituted to try to correct a driveability complaint as installation of higher heat range plugs can cause engine damage.
MODEL ENGINE VIN CODE SPARK PLUG GAP P/N
S/T 2.5L E R43CTS6 0.060 5613812
S/T 2.8L R R43CTS 0.045 5613810
M Van 2.5L E R43CTS6 0.060 5613812
M Van 4.3L Z R43CTS 0.035 5613810
C,K,G 4.3L N R43CTS 0.035 5613810
C,K,G 4.8L T R44T 0.035 5613867
C,K,G 5.0L H,F R43CTS 0.045 5613810
C,K,G 5.7L L,M R43CTS 0.045 5613810
C,K,G 7.4L W R44T 0.045 5613867
NOTE: Spark plugs should be ordered by part numbers. The plug type designation for a given part number may carry either a "C" or a dot to indicate a copper core electrode. AC-Delco is in the process of eliminating the "C" designation, and replacing it with a dot in all copper core plugs.
Number: 86-137
Section: 6D
Date: AUG., 1986
Subject: SPARK PLUG USAGE
Model and Year: 1986 LIGHT DUTY VEHICLES WITH GAS ENGINES
TO: ALL CHEVROLET DEALERS
The following information is being provided to assist dealers in the correct spark plug usage in 1986 Light Duty Trucks. Starting in 1986 many spark plug usages were changed. If it becomes necessary to replace the spark plugs, use the chart below for the correct plug application. It is not recommended that higher heat range plugs (example R43CTS to R44CTS) be substituted to try to correct a driveability complaint as installation of higher heat range plugs can cause engine damage.
MODEL ENGINE VIN CODE SPARK PLUG GAP P/N
S/T 2.5L E R43CTS6 0.060 5613812
S/T 2.8L R R43CTS 0.045 5613810
M Van 2.5L E R43CTS6 0.060 5613812
M Van 4.3L Z R43CTS 0.035 5613810
C,K,G 4.3L N R43CTS 0.035 5613810
C,K,G 4.8L T R44T 0.035 5613867
C,K,G 5.0L H,F R43CTS 0.045 5613810
C,K,G 5.7L L,M R43CTS 0.045 5613810
C,K,G 7.4L W R44T 0.045 5613867
NOTE: Spark plugs should be ordered by part numbers. The plug type designation for a given part number may carry either a "C" or a dot to indicate a copper core electrode. AC-Delco is in the process of eliminating the "C" designation, and replacing it with a dot in all copper core plugs.
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.