I sometimes wonder if it was rebuilt with a bit of modifications I didn't know about. I just assumed it was as close to original but I had no idea. Young & dumb, but it ran and have no reference as to if it was enhanced or not. Quite possible, That was the thing to do at the time. ' better than original' so the shop could brag. But dang, It goes like a bat out of hell. Subtle great power.Yeah 8 MPG is pretty bad....something seems amiss; perhaps a leak ? Even some of the big block muscle cars of the 60s
were better than that.
HOWEVER, if the car is a pleasure cruiser or a "once a month" driven garage queen and runs alright otherwise then perhaps monkeying with things may do more harm than good.