Quote:
Originally Posted by TransAm 474
Thanks Cliff, using the cross reference chart, it shows the AC R44S plug crosses to a NGK BP5S plug. Oreillys website shows a NGK XR4 plug for a 1970 RA III Trans Am. These are stock Heat Range I suppose, is the stock Heat Range fine for high compression, pump gas engine, or is it better to run a plug a step colder? Now, I have to find out what the difference is between the NGK BP5S and the XR4.
|
XR4 would be a vpower plug. Bp5s is a standard plug.
There is some overlap on heat ranges jumping from one company to the other. The bp5s falls from a cold side of a 46 to the high end of a 44 a/c plug. It is probably closes to a 45. A 6 starts at 44 and goes as cold as a 43.
A 6 would give the engine more thermal buffer. Thermal buffer is why we like to run on the colder side when it comes to plugs on performance engine with good compression. The 5 is more than likely ok, it is the non ok conditions like over heating or bad gas with high compression that your better off with the 6. If the engine never gets hot or some bad gas the 5 may never bother anything. Brisk has a pretty good explanation of heat ranges. Scroll down on the link and you can see that chart that shows a good depiction of thermal buffer and proper heat range.
https://www.briskusa.com/spark_plug_...at_range_chart