l am looking at early 70 is chevy is and would like to know what kind out mileage people have gotten out of their 396 and 454's.l am thinking of taking one cross country, and will most likely drive it everyday during warmer months.Things l am looking for are fuel consumption/reliability/ easiness to repair when things go wrong.

dont know but try toyota prius it will give u real goo milage

Let is answer the reliability question first. The chevy engine is a pretty bullet-proof engine but keep in mind that people bought 396 & 427 engines because they had huge horsepower ratings & would go like a ''bat out of hell''. Relatively speaking they r less expensive to work on then anything made now but u have to be mechanically inclined to undertake home repairs.

Gas mileage will depend on how u drive it. The temptation will be to gas it every chance u get because u can so the key to high mileage is a light foot. Most of the 70s 396 & 427s had 4 Barrel carbs but they were progressive carbs meaning that they would only go from 2 barrel operation to 4 barrel operation when the acceleration demands it. If u drive conservatively u should get decent gas mileage but u probably will need to run premium gas in these old beasts which will be more expensive then regular gas.

Some things to look for, does it have a ''dual pumper'' carb?. These eat gas like u own the refinery. Does it have solid lifters? This is an Extreme performance option & probably precludes the car having air conditioning. With that said, if u can get a good price on one of these classics they r great fun for cross country touring.

If you are looking for fuel economy you better pass on buying either one. They use a lot of gas.

old cars are easy to repair it doesnt take a computer wiz to figure them out(no pun intended) compared to cars today but mpg for them is relatively low the 396 ci big block probably got around 14 mpg on the hwy that is if its in great condition th 454 ci is around 8 mpgs not good for 2008 but gas is very low now so yeah you can take your chances reliability dont be expecting it to perform like a new car there over 35-40 yrs old

There is so much that can affect Mileage, Transmission, two speed power glide, three speed TH 350 or Th400, then anyone of the overdrives, If u use a standard, rear end gears help too, size or ur carburetor, Most of the cars l have had with 396 is & 454 is got around 8 to 14 miles per gallon, of course this all depends on how u drive along with the above listed factors too. Depending on what year the engine is l would replace the points distributor with HEI, less issues better reliability, A well taken care of chevy engine will last a very long time, l find Chevy engines to me r much easier to work on than other manufactures,

l hope this helps

l have to laugh out loud on this question..it seems to be an oxymoron question. First of all l have driven every 396/454 vehicle ever made, & at best u r only going to get 10 to 12 MPG up hill & or down hill..Second of all who would want to use a big block motor to go cross country at today is fuel rates. You r better off using a 350cid for reliability or one of the Japanese imports... l am not saying that the big blocks r unreliable, they just cost more to fix in some cases..