Which spark plugs can be used on a US STi 2.5lt, running 420-450BHP?
The OEM are number 6 cold, and are about 10mm longer than the plugs for the 2.0lt engines.

Christos

 

What part number are the std plugs?

 

I may not make sense here but would the OEM plugs not be longer due to the cylinder head diffrences between the EJ257 heads an JDM/UK EJ20 heads.

 

I expect so.
Hence the request for the std plugs PN

 

When your car due on the rollers Dyney? I would be interested in seeing the graph. I have a V3 Type-r that recently done its bearings in. I think the EJ257 is a good get up and go short block until its time for the crawford 2.2.

 

OK but won't be till mid Feb