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Any recommendations for what plugs to try on a 557" BBC with Brodix CNC'd BB2Xtra heads (13.5:1 compression, 110 octane fuel, 34-38 degrees timing depending on track conditions)?
 

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Ngk #8 vpower plugs and #9 or#10 on spray plug # vairies on head
 

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I'm running Autolite AR 3933 in my 565 and they work fine. I can't run an extended tip due to piston clearance but if you can I'd run an extended tip. You don't say if you can. RM
 

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I have the same heads and run the NGK R5671A-8's Brodix suggested.

When I cross reference that to an Autolite, it comes up as an AR3934. Would those be hotter or colder than the AR3933's? What would be better for an N/A car running 111 octane?
 

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My motor has no power adders and I'm running Torco or Sunoco Blue 112. My motor is 14.7 to 1 comp. 3932 is colder than 3933 and a 3934 is hotter. I have also run a c59 Champion which seemed to run OK but sounded different at idle and I didn't like that. They burned OK and ran the same ETs but I went back to the Autolites. RM
 
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