i was originally running iron head 906’s on my street driven flat top piston 451 B motor and used the short reach NGK big block XR5 plugs (.375” reach with projected tip). When fighting a pinging issue last summer I had switched to a colder NGK plug with the same reach (-8 since NGK Heat range is higher # equals colder, with .375” reach). I have since learned that driving around town 99% of the time with a lot of non-highway miles with this colder plug and my 10.2:1 compression motor in California 91 octane high ethanol summer blend can load up the plugs so I ordered and received some NGK’s in the -7 heat range (NGK 5671-7). These are non-projected flat tip but I was suprised to see that these have a much longer .75” reach. Reading up on this it seems that the longer reach .75” plug is what is needed for the aluminum headed big block just like an iron headed small block plug and all along I have been using the short reach plug as I had for my big block iron heads.
What problems may I expect if I continued to run the shorter reach plug with the aluminum head and by swapping over to the longer reach non projected plugs for 2500 rpm street driving can I expect to gain anything (cooler running, power difference, less chance of pinging, etc)?
After swapping plugs do I need to do any other engine tuning after the install if my tune was perfect with the short reach plugs?
What problems may I expect if I continued to run the shorter reach plug with the aluminum head and by swapping over to the longer reach non projected plugs for 2500 rpm street driving can I expect to gain anything (cooler running, power difference, less chance of pinging, etc)?
After swapping plugs do I need to do any other engine tuning after the install if my tune was perfect with the short reach plugs?