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That cam is killing you. If there's one thing the 284/484 was not made for, it's fuel mileage. That's a big cam for a small block and it's got a narrow LSA. You'll never get good mileage with it.





I think the 8 to 10 mpg estimates are pretty close. Still better than the 6 to 7 I get
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Would i see a big performance increase if i but 340 x heads on this car with a 8 3/4 posi rear?



I doubt you'de see a perf gain from the heads, but it's hard to say. Has either set been ported>

The ring gear size won't gain you anything. It's the ratio. Stick with a sure grip instead of GM posi unit though.

An upgrade to an 8 3/4 is probably a necesity, simply from a strength standpoint. I had a friend with an aspen with a 340 in it. It broke a couple of those 7 1/4's in really short order.