YT engine code, casting number 9786133 (no transfer lug, 3 freeze plugs), and 670 heads. From everything I can find, it's a 1967 325 HP 400, 10.75:1 compression ratio, 2.11 intake valves and 1.77 exhaust valves. The YT code is the correct code for the car (it was originally an automatic), but unfortunately it is not the original engine. I am planning on only putting ~2000 miles per year, but am planning on putting in the hardened seats anyway. My machinist is working cheap, as he owes me... I plan on replacing the rods, but I don't want to back down to the mid 8's for the compression ratio. Is 91 octane pump gas OK with the 10.75:1 or will I run into detonation? There is 110 available at the pump in my area due to the close proximity to Road America, but the cost is triple the 91 octane. Like I said, I don't need it to be fire-breather, but I want it to sound good, and perform well on the street. Mama doesn't let me get into the throttle much, but she's not always with me .
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