edge04

iTrader: (9)

Know spark plugs have been discussed a lot but don't see many running 8's so thought I would ask. I plan to run NGK R5724-8's on my iron 408 TT 63's with meth. Should push 800 on 93 octane. Was thinking gaping them at 40 but wondering what you all would recommend. Thanks

BlackWS666

iTrader: (31)

I run 8's. Gapped to .028". 408 single GT55. Not sure if .040" you would experience any spark blowout, depends on the amount of pressure you plan to run, but I have never had a issue and ive ran up to 28#. No problems here.

trans2000am

iTrader: (49)

Running 8's gapped at .025

edge04

iTrader: (9)

well time to pull them out and re-gap. I'll set to 28 and go from there. thanks

Gabbiani

iTrader: (20)

.040 is a little big for boost. I've had some cars break up with just 10psi.

Forcefed86

iTrader: (4)

The "Best gap" is the always largest you can run without the sprak blowing out.

You don't see the tapered OE LS head plugs in an 8,9 or 10 commonly because they are not "resistor" plugs. The 8 and colder aren't really designed to be run on the OEM ignition system. (not that some don't do it)