390 4V in my '64 and 10 mpg. Sure glad I don't have to drive it but to the store and back etc. I should have filled the tank rather than put $20 in it back when the gas was $2.75 then I think. It's $3.17 now for the cheap stuff. Still I wouldn't give up my 390 for nothin. Just need a whole dif car that's small.
The 521 is nothing less than disgraceful on fuel. And at $4.10 U.S. a gallon for the 98 octane stuff,you just about need a bank loan to do a cruise down the esplanade.
But, don,t the jap and euro tourists love it!
Oh, hang on , so do I.
390 originally 2v. Now .030 over (396ish) Edelbrock performer RPM top end, crane cam, speed pro pistons around 9.4:1 compression, and a holley 4v 750cfm vac secondary carb. I don't think I need to metion it but it's a BIG BLOCK.