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Discussion Starter #1
We took the stock 307 and replaced the PG with a TH350. Added a Holley 570 and edlebrock intake to match. Didn't rejet or anything, just bolted them on. Running true dual exhaust (flowmaster) but thru stock exhaust manifolds since we couldn't get the header to fit due to the AC box. Our gas mileage isn't all that great. About 10-11 in town. We didn't change the rear end gear. Also complete electronic MSD ignition/distributor etc.

Does that sound about right?

Thanks
 

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Maybe a little low, but not terrible. 307's are bad at making power and being efficient. The worst of all worlds lol.

I had the best luck using a 500 cfm Edelbrock. A 200 4r and 2.73's netted me ridiculously good numbers all the way around. The low first gear and overdrive made for a very pleasant and efficient ride.

BUT... that being said. A proper tune and keeping your foot out of it, you might get 14 mpg or so out of it. Stock 283's get about 20 on the highway, so don't get too optimistic.

Kev
 

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pull a couple plugs and make sure it isn't running too rich. 20-25 highway wouldn't be out of the question if it was setup perfectly. tire size, gear ratio, converter slippage, etc. will make a huge difference. assuming it's vacuum secondary, check your secondary spring to make sure it's not so light that it's open all the time. ultimately, you'll have to experiment to get it perfect, but 10-11 isn't too bad for a city mileage baseline, considering you haven't messed with the carbuerator
 

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Discussion Starter #4
Thanks for the info...haven't really checked highway miles but the RPM's at 60 suck! Any idea what I should expect at 60 mph as far as RPM's with the stock rear end in it?
 
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