rajsid

Which is a hotter plug? R45TS or R43TS?
I am getting mixed answers from the internet.

Looks like all spark plug manufacturers does not follow the same convention. Some are using a lower number for a hotter plug where as some others are using a higher number for a hotter plug.

I am going to to stick with AC Delco and I would like to understand how their heat range numbering system works.

Their site does not say much on this topic
http://www.acdelco.com/parts/sparkpl...tification.jsp

mds3013

If memory serves the higher number is hotter. The insulator on the combustion chamber side will be smaller as plug heat range increases. mds...

midyearvette

the 45 is 2 stages hotter than the 43

Mike Ward

Correct.

rajsid

Thanks guys.

Spark plug heat range has nothing to do with engine heat... correct?

midyearvette

correct.....a cold plug transfers more of it's heat to the water jacket and a hot plug transfers less....it's that simple...

rajsid

Thanks again guys.

81pilot

The spark plug heat range has no relationship to the electrical energy transferred through the spark plug. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of NGK spark plugs is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.
So be sure to check manufacturers they vary as you can see on the NGK's.



The lower insulator nose is always longer on the hotter plug...

Ironcross

actually the link does tell you all you need to know..and does a good job...

'R designates a resistor plug
'4 is the thread size
'5 is the heat range
'T is a tapered seat plug {peanut plug} no gasket necessary
'S means extended tip....
Thus 'R45TS'...this is listed in the link

Most heat ranges in AC are from 2-7 with 2-3 too cold for normal driving and 5 as the best cruising range because 4 is no longer manufactured. and 6-7 heat range is rarely used

maybe a little more explanation, The 'S extended tip is available in all heat ranges and has caused interference in some engines with domed pistons in "early" SHP engines therefore when in doubt a plane 'R45 without the 'S works best

eagle275

man, I learn something here everyday!

RobertHuggins

http://e3sparkplugs.com/hot-spark-pl...d-spark-plugs/

This web page tries to get the point across; but fails in a couple of ways.

They use the word insulator as both the electrical insulator and the heat insulator in the same sentence with no distinction.

Yes, the ceramic material that insulates the electrical signal to the center electrode from the threads that ground the plug is also a heat insulator. But also the amount of ceramic material and amount of contact area between the ceramic material and the center electrode controls the "heat sink" aspect that controls heat range. Thus the ceramic is both an electrical insulator and a heat insulator.

The "art" or "rocket science" of making a plug involves the shape of the ceramic. You never want the ceramic to break off and go through the engine. You never want to unscrew a spark plug and see that a chip of the ceramic is missing from a plug. Yet the ceramic must be designed to allow the plug tip to get hot enough to be self cleaning yet not too hot to cause pre-ignition. If it gets so hot that it is acting like a glow plug, then you will cause engine problems and you will likely see a melted plug center electrode.

A lot of people use the AC Delco "43" and "45" plugs in their C3 Corvettes. The R45TS is a hotter plug than the R43TS. If you are seeing deposits on your R43TS plugs, you really do not know if it is because your carb is too rich, oil is getting into the cylinder, or the plug is not getting hot enough to be self cleaning.

The earlier years of C3 corvettes might have high enough compression where a hotter plug could cause pre-ignition; but the later years of C3 corvettes were certainly low enough compression that it should not be a problem.

So go ahead and try a set of R45TS plugs if your R43TS plugs are showing heavy deposits on them.