13:1 Compression Pistons in 340 Small Block

Garrett Ellison said

The last build I was in with compression in that neighborhood (14:1!) took two cans of 104-Plus to 20 gallons of premium fuel... I won't even go into all the complications and legalities involved with aviation fuel, but being it takes e 85 components to withstand long term exposure to that devils juice, your better off with the legal e85 plan.

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I run E-85 on a 12.5:1 compression 451 short deck BB build. It certainly solves the denotation concerns. As well as runs cooler. (Which can be a little problematic on colder morning's warm up.) It does use about 15-20% more fuel than gas. But it's also 20% less expensive than pump 91. So it's a win compared to any race gas strategy. Carb(s) must be meter blocked for increase fuel need. Today's EFI can easily be mapped for E-85 electronically.

It doesn't keep as well as gas. You're best bet is to run it completely dry before any storage of 30 day or more. (This is true for race gas after 6 months as well.)

E-85 availability is high here in Minnesota. Thus is a very attractive alternative for higher boost or compression builds.

Just sharing my observations.