I wanted to go 2 steps colder from the xr4 so I ordered the ngk 5670-6. Only thing is they’re non resistor.. If they foul then I can go xr5,, if they don’t foul I should be good and safe.
The coloring is probably from whatever fuel they used for the 2 hours of run time after the dyno day…. I’m assuming 110. On the dyno , previous to me showing up ,they had been running 110 gas and I brought a mixture to try of av and 93. The mixed gas made a little more power than the 110 and the mixed is what I use on the street . It had a rear main seal leak on the dyno so after I left they tore it apart and installed another rear main seal, put it back on the dyno and ran it on and off for two hours to make sure the rear rear main did not leak this time.. I’m going to pull the rest of the plugs today and take some pictures
Ramair judge…Autolite 86 sounds like a cross over to the ngk xr4. I had good luck with the 85 but they don’t make them anymore. I’m assuming you wanna run a plug as cold as you can without fouling?
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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007
(cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD
1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.45 @ 88.1 mph on slippery street tires.Bad 2.19 60ft.Owned since 86'
Last edited by scott70; 06-18-2026 at 08:03 AM.
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