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:for the spark plugs and haveput down very reliable, high hp builds.. over 650rwhp, that are driven pretty much daily. According to the JWT Engineer, Nissan did not allow enough space for coolant in that trianglular area. During High Loads, the coolant "flashes over" which means that the coolant is not doing it's intended function. When this occurs, The Combustion chamber lifts in this area (un-seals). the head will return to normal, if the condition (detonation) is relieved immediately, otherwise, permanent set (distortion) will occur.
The JWT Engineer recommended using Propylene Glycol instead of Ethylene Glycol for anti-freeze to remedy this condition.
IF you are running a "De-Bossed" head, you should be:
Using Propylene Glycol anti-freeze (as this type will not "flash over").
Adjust the Spark plug length to prevent having threads exposed (Sharp Edges) within the Combustion Chamber.
Index the Spark plugs. The design is what it is: 25 year old technology.
I recommend to take the opportunity to view a VG30 Head that has been sectioned. It will (and should) take some time to study the design, at which time the design "flaws" become apparent. Also noteworthy is that the Nissan Engineers corrected this condition on the VQ...
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