I'd run some non gasahol & see if that's strickly the prob. what changes right b 4 the prob started? Gasahol absorbs water so no water treatment needed. which side did you block the heat riser on as it kicks back ex for heat from the pass side. A felpro ~3/8" carb base gasket will definitely help and finding/making a laminated wood spacer is the best. I run 89 octane E10 (gasahol) and 87 octane non gasahol regular w zero probs & runs identical either way in a DD 318 65 dart w streetmaster/1406 Eddy but it does run cool.