Before my rebuild my basically stock 67 400 with 670 heads and the 068 cam required me to mix 110 50/50 with 93 in order to stop pinging. I have since rebuilt and have a small dish in the pistons as well as some mild porting to get the chamber to around 98cc and 9.5 to 1 compression. I have been running well on straight 93 octane now.
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67 GTO Hardtop
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