Originally Posted by
Tony Newland
The "C" series of plugs are very cold and only typically used in onroad or high nitro applications. We only use the "H" series of plugs in our engines as well as the previous GRP's.
They have the same taper etc. I would recommend using either the H6 (most common) or H7 if you need a colder plug.
Our plugs are available at Amain or from us direct
GRP only used a "C" series of plugs and the C5 (medium) and C6 (cold) were recommended for the .21 tuned. Most of the GRP's came out of the box with either a C5 or C6 installed. Been running he GRP C5 with good result, but you can notice they are a bit colder then other companies medium rated plugs.
Anyway, thanks for the reply Tony, i'll be ordering some TP H6 plugs
