LARIDERS

I have been looking on the web. And can't find what I need. I want a ac delco plug that is standard and one degree colder than stock the stock is 41-985 can't find anything that will list a standard plug. Any help would be great.

maxxman04

not gonna find a listing for heat ranges for these plugs. it's not coded in the number. 41 is a stocking/tracking number for ac delco. 985 is a 900 series plug, a double platinum type. 85 is the application number, being the 85th 900 series plug made. trying to use a colder or hotter plug in a computer controlled car may cause damage.

LARIDERS

they do have a heat range in the number the number 5 is the heat range. I just can't use a platinum plug. I need a old school spark plug. if I use a stock plug I will cause alot of damage to my truck and I will melt the plugs. I need to cross the stock number of a platinum plug to a standard old school plug. and can't find the info anywhere.

cooter26

I think you are wrong on the heat range for the AC delco plug. The last # is the heat range for Autolite plugs but not AC Delco.

On AC Delco plugs the second # is the heat range.



The ACDelco Spark Plug Identification Table

Prefix and suffix letters are used to identify a specific type plus the numbers relate to thread size and heat range. For example, the R45TS spark plug shown is:

• R = Resistor
• 4 = 14 mm Thread
• 5 = Heat Range
• T = Taper Seat
• S = Extended Tip

<TABLE cellSpacing=1 cellPadding=0><CAPTION>Plug Identification Table Prefix</CAPTION><THEAD><TR><TH>Identification Code</TH><TH>Description</TH></TR></THEAD><TBODY><TR><TH>B</TH><TD>Series Gap</TD></TR><TR><TH>C</TH><TD>Commercial</TD></TR><TR><TH>CS</TH><TD>Chain Saw</TD></TR><TR><TH>F</TH><TD>Fine Line 14 mm 5/8" Hex</TD></TR><TR><TH>M</TH><TD>Marine</TD></TR><TR><TH>LM</TH><TD>Lawn Mower type</TD></TR><TR><TH>R</TH><TD>Resistor</TD></TR><TR><TH>S</TH><TD>Shielded (5/8-24 thread)</TD></TR><TR><TH>V</TH><TD>Surface Gap</TD></TR></TBODY><TFOOT><TR><TD colSpan=2>Prefixes are sometimes combined e.g., VB, CR</TD></TR></TFOOT></TABLE>Numbering

• 1<SUP>st</SUP> number denotes THREAD SIZE
• 2<SUP>nd</SUP> number denotes HEAT RANGE

In the early 1990s, an all-numeric, identification code was developed to ensure that the proper spark plug would be selected for replacement in specific engine applications. The numeric code does not in any way correspond to the heat range of the spark plug. Therefore, selection of a spark plug with a different code number is not recommended. The heat ranges may be drastically different between two different plugs, and engine damage or poor performance may result. See your local installer or retailer for details.
The prefix “41” stands for the manufacturer’s product line (e.g., 41 = spark plug)
Numbers after the prefix indicate the type of spark plug and also the specific application:

• 100 – 199 = Iridium
• 600 – 699 = Resistor
• 800 – 999 = Double Platinum

<TABLE cellSpacing=1 cellPadding=0><CAPTION>Plug Identification Table Suffix</CAPTION><THEAD><TR><TH>Identification Code</TH><TH>Description</TH></TR></THEAD><TBODY><TR><TH>A</TH><TD>Clip Gap</TD></TR><TR><TH>C</TH><TD>Copper Core Center Electrode</TD></TR><TR><TH>C</TH><TD>Colder Version of M44 Plub</TD></TR><TR><TH>E</TH><TD>Special Design Electrode Extended Tip</TD></TR><TR><TH>F</TH><TD>1/2" (12.7 mm) reach</TD></TR><TR><TH>FF</TH><TD>1/2" (12.7 mm) reach, fully threaded</TD></TR><TR><TH>G</TH><TD>Pin Gap (cold-running)</TD></TR><TR><TH>I</TH><TD>Iridium Center Electrode</TD></TR><TR><TH>J</TH><TD>Boot Release Agent, Anti-Seize Compound</TD></TR><TR><TH>K</TH><TD>Special Design</TD></TR><TR><TH>L</TH><TD>Long Reach
7/16" (11.1 mm) reach, (14 mm) thread
3/4" (19 mm) reach, (18 mm) thread
3/4" (19 mm) reach, (14 mm) thread (fineline) </TD></TR><TR><TH>LT</TH><TD>Long reach, .715" (18.16 mm), Tapered Seat</TD></TR><TR><TH>M</TH><TD>Special Design Electrode</TD></TR><TR><TH>N</TH><TD>3/4" (19 mm) reach, 3/8" (9.5 mm) thread length</TD></TR><TR><TH>R</TH><TD>Resistor (Sport Vehicle Plugs)</TD></TR><TR><TH>S</TH><TD>Extended Tip</TD></TR><TR><TH>S</TH><TD>7/8" (22.3 mm) Moderate Long Reach
23/32" (18.25 mm) </TD></TR><TR><TH>T</TH><TD>Tapered Seat Shell Design</TD></TR><TR><TH>TS</TH><TD>Tapered Seat with extended tip</TD></TR><TR><TH>XL</TH><TD>Extra Long Reach, 3/4" (19 mm) fully threaded</TD></TR><TR><TH>Y</TH><TD>3-Prong Cloverleaf Electrode</TD></TR><TR><TH>Z</TH><TD>Special Gap (usually denotes wide gap)</TD></TR><TR><TH>5</TH><TD>.050" (1.3 mm) gap</TD></TR><TR><TH>6</TH><TD>.060" (1.5 mm) gap</TD></TR><TR><TH>8</TH><TD>.080" (2 mm) gap</TD></TR><TR><TH>100</TH><TD>Iridium</TD></TR><TR><TH>600</TH><TD>Resistor Type</TD></TR><TR><TH>800</TH><TD>Platinum Type</TD></TR><TR><TH>900</TH><TD>Double Platinum Type</TD></TR></TBODY><TFOOT><TR><TD colSpan=2>Suffixes are combined to form such AC suffix designations as FG, XLS, TS, FFM, TSX, SZ, etc.</TD></TR></TFOOT></TABLE>

maxxman04

thanks cooter26, that's the info i was looking for to help LARIDERS.

LARIDERS

thanks for the info. the bigger problem was to try and cross a ac delco number with another ac delco number. I think I found the plug I am going to try next. I had went two ranges colder to start with, but after looking at the plugs I wanted to try just going one heat range colder. from looking around I will have to go two ranges colder. I had champion plugs in there. ( I was told they wokred well) but I want to try ac delco as I have always used them in the past. I could not find a listing for my truck that would give me a plug that was a copper plug. I am going to try a r42lts delco. I wanted a r43lts. just have to see if it works. I change the plugs 3 times a year anyway. thanks for the help.

73shark

Why do you change plugs 3X/yr?

LARIDERS

I really only need to change once or twice a year, but I seem to do it about three times. the truck burns the plugs up. high spark plus boost makes them not last that long. plus they are a standard copper plug. last I checked in 2,000 miles I burned .005 off the plug. that made my gap.042