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AC Delco Gold Spark Plug 21
Part # 21
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AC Delco Gold Spark Plug 21
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Vehicle Compatibility
No compatibility data available for this part.
Specifications
Brand: ACDelco
Part Number: 21
Part Type: Spark Plug
Condition: New
Center Electrode Core Material: Copper
Center Electrode Tip Material: Platinum
Core Nose Length: 0.560 IN
Electrical Terminal Type: Non-Removable Nut
Ground Electrode Core Material: Nickel
Ground Electrode Tip Material: Nickel
Hex Type: Hex
Length (In): 4.13 in
Outside Diameter: 1.983 IN
Resistor Type: Yes
Sealing Surface Type: Nitrile
Seat Type: Flat
Shaft Diameter: 1.000 IN
Thread Diameter (In): 0.551 in
Thread Diameter (Mm): 14.0 mm
Washer Type: Crush
Washer(S) Included: Yes
Center Electrode Design: Standard
Faq - Answer 1: Yes, this interval depends on what type of spark plug your vehicle requires. Refer to your owner's manual or contact your vehicle's manufacturer for more information.
Faq - Answer 2: Yes, if it is the scheduled time for spark plug replacement.
Faq - Answer 3: Yes. Diesel engines require glow plugs because diesel engines operate differently than gas engines. ACDelco Professional Glow Plugs are specially designed to give diesel engines the heat they need for
Faq - Answer 4: Yes. When ACDelco spark plugs are manufactured, they are pre-gapped to the correct gap specification.
Faq - Answer 5: Not always, but you should inspect your spark plug wires for wear when replacing your spark plugs. Refer to your vehicle owner's manual or contact the manufacturer for more information.
Faq - Answer 6: Yes, pre-ignition can cause serious damage to your engine. Pre-ignition is the ignition of fuel before the actual spark occurs, which causes a rapid temperature rise in the combustion chamber that can
Faq - Answer 7: No, cleaning your old spark plugs is not recommended. Dirty, fouled spark plugs may also have broken or chipped insulator tips, worn electrodes, or worn or missing side wires. These conditions severel
Faq - Answer 8: Yes, ACDelco has marine spark plugs for many applications.
Faq - Question 1: Is there a recommended interval for changing my vehicle's spark plugs?
Faq - Question 2: Should I change all of my vehicle's spark plugs at the same time?
Faq - Question 3: Does a diesel engine require a different type of plug than a gas engine?
Faq - Question 4: Are ACDelco spark plugs pre-gapped?
Faq - Question 5: When I replace my spark plugs, should I also replace my spark plug wires?
Faq - Question 6: What is pre-ignition and can it damage my engine?
Faq - Question 7: Can I just clean my spark plugs instead of replacing them?
Faq - Question 8: Does ACDelco have marine spark plugs?
Features Benefits - Bullet 1: Solid state suppressor, with two-piece glass and brass seal, can help reduce radio frequency interference, regulates spark energy for long electrode life, and helps protect against high combustion pre
Features Benefits - Bullet 2: Pure copper core provides great heat transfer and helps maximize plug durability
Frequently Asked Questions
We're always here to help. If you can't find your answer, ask Rydon - our AI assistant will help you out.
What vehicles does this Spark Plug fit?
This ACDelco Spark Plug (Part #21) fits specific vehicles. Use the compatibility checker on this page to verify fitment for your vehicle.
Is this an OEM or aftermarket part?
This is a premium aftermarket Spark Plug by ACDelco, designed to meet or exceed OEM specifications with strict quality control standards.
What warranty is included?
This ACDelco Spark Plug is backed by a 24-month limited warranty covering defects in materials and workmanship from date of purchase.
How long does shipping take?
Free standard shipping on all orders. Most orders ship within 1-2 business days and arrive within 3-5 business days.
Can I return this if it does not fit?
30-day money-back guarantee. Return unused parts in original packaging for full refund.
Product Specifications
Brand
ACDelco
Part Type
Spark Plug
Center Electrode Tip Material
Platinum
Electrical Terminal Type
Non-Removable Nut
Part Number
21
Center Electrode Core Material
Copper
Core Nose Length
0.560 IN
Ground Electrode Core Material
Nickel
Center Electrode Core MaterialCopper
Center Electrode Tip MaterialPlatinum
Core Nose Length0.560 IN
Electrical Terminal TypeNon-Removable Nut
Ground Electrode Core MaterialNickel
Ground Electrode Tip MaterialNickel
Hex TypeHex
Length (In)4.13 in
Outside Diameter1.983 IN
Resistor TypeYes
Sealing Surface TypeNitrile
Seat TypeFlat
Shaft Diameter1.000 IN
Thread Diameter (In)0.551 in
Thread Diameter (Mm)14.0 mm
Washer TypeCrush
Washer(S) IncludedYes
Center Electrode DesignStandard
Faq - Answer 1Yes, this interval depends on what type of spark plug your vehicle requires. Refer to your owner's manual or contact your vehicle's manufacturer for more information.
Faq - Answer 2Yes, if it is the scheduled time for spark plug replacement.
Faq - Answer 3Yes. Diesel engines require glow plugs because diesel engines operate differently than gas engines. ACDelco Professional Glow Plugs are specially designed to give diesel engines the heat they need for
Faq - Answer 4Yes. When ACDelco spark plugs are manufactured, they are pre-gapped to the correct gap specification.
Faq - Answer 5Not always, but you should inspect your spark plug wires for wear when replacing your spark plugs. Refer to your vehicle owner's manual or contact the manufacturer for more information.
Faq - Answer 6Yes, pre-ignition can cause serious damage to your engine. Pre-ignition is the ignition of fuel before the actual spark occurs, which causes a rapid temperature rise in the combustion chamber that can
Faq - Answer 7No, cleaning your old spark plugs is not recommended. Dirty, fouled spark plugs may also have broken or chipped insulator tips, worn electrodes, or worn or missing side wires. These conditions severel
Faq - Answer 8Yes, ACDelco has marine spark plugs for many applications.
Faq - Question 1Is there a recommended interval for changing my vehicle's spark plugs?
Faq - Question 2Should I change all of my vehicle's spark plugs at the same time?
Faq - Question 3Does a diesel engine require a different type of plug than a gas engine?
Faq - Question 4Are ACDelco spark plugs pre-gapped?
Faq - Question 5When I replace my spark plugs, should I also replace my spark plug wires?
Faq - Question 6What is pre-ignition and can it damage my engine?
Faq - Question 7Can I just clean my spark plugs instead of replacing them?
Faq - Question 8Does ACDelco have marine spark plugs?
Features Benefits - Bullet 1Solid state suppressor, with two-piece glass and brass seal, can help reduce radio frequency interference, regulates spark energy for long electrode life, and helps protect against high combustion pre
Features Benefits - Bullet 2Pure copper core provides great heat transfer and helps maximize plug durability
Features Benefits - Bullet 3Platinum on center electrode enables superior spark characteristics and can reduce voltage requirements of the ignition system
Features Benefits - Bullet 4Ribless insulator helps optimize plug to boot sea
Features Benefits - Bullet 5Some ACDelco Gold parts may have formerly appeared as ACDelco Professional
Features Benefits - Bullet 6Premium aftermarket replacement part
Features Benefits - Bullet 7Manufactured to meet specifications for fit, form, and function for General Motors vehicles as well as most makes and models
Ground ConfigurationStandard
Ground Electrode Quantity1
Ground Electrode Tip DesignStandard
Height (In)1.19 in
Hex Size (Mm)16 mm
IndexedNo
Indicated Mean Effective Pressure (Imep)270 4S
Insulator Height2.047 IN
Manufacturer Heat Range8
Pre-Gap Size0.045 IN
Product DescriptionACDelco Gold (Professional) RAPIDFIRE Spark Plugs are a high quality alternative to Original Equipment (OE) parts. These RAPIDFIRE Single Platinum Performance Spark Plugs are designed for everyday use
Reach1.043 IN
Signs Of Wear Troubleshooting - Section 1 - Bullet 1Your engine having trouble starting, hesitating, or cutting out
Signs Of Wear Troubleshooting - Section 1 - Bullet 2Engine misfire
Signs Of Wear Troubleshooting - Section 1 - Bullet 3Sluggish engine performance, loss of engine power, or decreased fuel economy
Signs Of Wear Troubleshooting - Section 1 - Bullet 4Lack of acceleration or loss of speed when driving uphill under load
Signs Of Wear Troubleshooting - Section 1 - Bullet 5Cracks in the upper or lower portion of the spark plug insulator
Signs Of Wear Troubleshooting - Section 1 - Bullet 6Chipped or broken insulator tips
Signs Of Wear Troubleshooting - Section 1 - HeaderSigns of wear for spark plugs include but are not limited to:
SkirtNo
Weight (Lb)0.4 lb
Width0.406 IN
Width (In)3.62 in
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Part # 21AC Delco Gold Spark Plug 21
Brand ACDelcoCondition NewSpark Plug24-mo warranty
$595
$7.95SAVE 25%
Dealer charges $11.53SAVE 48%— You save $5.58
In Stock·10 or more available
QTY
1
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Shipping
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OE REPLACEMENT
AC Delco Gold Spark Plug 21
|
Part #:21
|
Spark Plug
$5.95In Stock
$7.95Save 25%
Quantity:
1
In Stock·10 or more available
Shipping calculated at checkout · Est. arrival Fri, Aug 14 to Fri, Aug 14
Ships To:Key Features
OEM-Equivalent QualityMeets/exceeds factory specs
American BusinessMaryland since 1986
24-Month WarrantyLimited coverage on every part
Free Same Day ShippingWe ship all orders the same business day before cutoff
Product HighlightsBeta
Reading the catalog · checking interchanges · researching…
What vehicles does this Spark Plug fit?
This ACDelco Spark Plug (Part #21) fits specific vehicles. Use the compatibility checker on this page to verify fitment for your vehicle.
Is this an OEM or aftermarket part?
This is a premium aftermarket Spark Plug by ACDelco, designed to meet or exceed OEM specifications with strict quality control standards.
What warranty is included?
This ACDelco Spark Plug is backed by a 24-month limited warranty covering defects in materials and workmanship from date of purchase.
How long does shipping take?
Free shipping on orders $50+. Most orders ship within 1-2 business days and arrive within 3-5 business days.
Can I return this if it does not fit?
30-day money-back guarantee. Return unused parts in original packaging for full refund.
AC Delco Gold Spark Plug 21
Part # 21
Main Image
Click to expand
1 / 4
$595
$7.95SAVE 25%
Dealer charges $11.53SAVE 48%— You save $5.58
In Stock·10 or more available
QTY
1
Fast
Shipping
Shipping
30-Day
Returns
Returns
24-Mo
Warranty
Warranty
Expert
Support
Support
OE REPLACEMENT
AC Delco Gold Spark Plug 21
|
Part #:21
|
Spark Plug
$5.95In Stock
$7.95Save 25%
Quantity:
1
In Stock·10 or more available
Shipping calculated at checkout · Est. arrival Fri, Aug 14 to Fri, Aug 14Ships To:Key Features
OEM-Equivalent QualityMeets/exceeds factory specs
American BusinessMaryland since 1986
24-Month WarrantyLimited coverage on every part
Free Same Day ShippingWe ship all orders the same business day before cutoff
What vehicles does this Spark Plug fit?
This ACDelco Spark Plug (Part #21) fits specific vehicles. Use the compatibility checker on this page to verify fitment for your vehicle.
Is this an OEM or aftermarket part?
This is a premium aftermarket Spark Plug by ACDelco, designed to meet or exceed OEM specifications with strict quality control standards.
What warranty is included?
This ACDelco Spark Plug is backed by a 24-month limited warranty covering defects in materials and workmanship from date of purchase.
How long does shipping take?
Free shipping on orders $50+. Most orders ship within 1-2 business days and arrive within 3-5 business days.
Can I return this if it does not fit?
30-day money-back guarantee. Return unused parts in original packaging for full refund.
About This Spark Plug
This ACDelco automotive component is engineered to meet or exceed OEM specifications for reliable performance and long service life.
Key Features
- Meets or exceeds OEM specifications
- Direct-fit replacement design
- Rigorously tested for durability
- Professional-grade construction
- Backed by manufacturer warranty
Signs This Part Needs Replacement
- •Unusual noises from the component area
- •Decreased vehicle performance
- •Warning lights on dashboard
- •Visible wear or damage
- •Failed vehicle inspection
ACDelco
Trusted Automotive Brand
ACDelco is a trusted manufacturer of quality automotive parts.
View all ACDelco productsInstallation Guide
Moderate
1-3 hours
Tools Needed
Basic hand toolsTorque wrenchVehicle service manual
Frequently Asked Questions
WARNING: Handling passenger or off-highway motor vehicle parts can expose you to chemicals such as phthalates and lead, which are known to the State of California to cause cancer and reproductive harm. To minimize exposure, service the vehicle in a well-ventilated area, wear gloves, and wash your hands. For more information see www.P65Warnings.ca.gov/motor-vehicle-parts