The Stovebolt Site Forums The Shop Area Engine Shop Ideas for fuel economy???

I'm starting to daydream about my next project, which I hope will be a '55.5 to '59 and I'm looking for ideas. I don't mind a couple of extra horses but I'm more concerned about being able to afford to drive it. I have a 3sp manual w/ OD sitting in my garage and I have access to a '77 model 250 6 cyl. I'm looking for recommendations on the best 6 cyl engine to get good gas milage and any upgrades or modifications that can be made to stretch this #3+ gas as far as possible. Any help will be appreciated.

This may help:

http://www.thecarburetorshop.com/Troubleshooting.htm#Fueleconomy

Jon.

Good gearing is one of the major keys to good mileage. I'd use the 3sp/OD tranny, they work great. That and a 3:73 or so rear end should get you around 20mpg with the 250, or even with a well-tuned SBC. Of course, the weight of your right foot on the accelerator has a lot to do with it too.

Not to mention tire height can really contribute. Keeping your tires aired up to the correct PSI and keeping your brakes adjusted properly.

Your overdrive transmission with a 3.90 rear end will give you a good low end and 2.73 high way in o.d.

How do the various 6's compare in fuel economy? I drove a 292 once that I really liked but I think it used a lot of gas. Are there modifications that will help; such as electronic ignition, better carburetor, dual exhaust? I definitely plan to use a 3sp w/od tranny and I generally drive conservatively.

Your definately on the right track. I was getting about 12 mpg pretty consistently when my truck was all stock. I've since added dual exhaust, O.D., good radials, and HEI. I now get about 18 and am able to comfortably drive it at 70mph on the freeway. Some get better, but I have a heavy foot

Whatever you run, raise the compression to 8.5:1 to run off regular unleaded and keep a mild cam in it, that will help a lot. Don't overlook the ignition, an electronic ignition or dual points kit will keep the timing and dwell in spec for longer and you won't have to tune it up as often. Maybe even have the advance curve modified if your engine can stand it. Ultimate would be to convert to fuel injection but that's a pretty big project.

Last time I posted my fuel economy numbers people told me I was lying so I won't, but with a dual point kit and a well sorted out Rochester B with a 261 in a half ton I was doing pretty well. Keep narrow, tall radial tires and it will steer nice too.

And it is a good idea to run a "base line" before each modification; so you can actually measure results. Sometimes you surprise yourself!

Jon.

Some good ideas here. The stock 292 came with 8.0:1. You can do as I have done and put in propane 9.0:1 pistons. I should have had the block decked some but didn't think it needed it. It wasn't that much more for them over stock ones. My engine isn't broke in yet so the mileage is anybodies guess. The timing is still retarded and the valves are loose and will have to be re-adjusted. Headers are next and a 500 cfm is a big as I am going. Don't need a 600 or larger toilet. I put in a Pertronix Ignitor and what a difference with my MSD. Works great! Oh BTW, the 77 will be an integral manifold type. They are not a good idea. You cannot change them to the older style. The integrals ran crappy. Limited on what you can do with them. 74 or older is what you want unless you are going to a 292. Stock cam with headwork will do just fine and make it breathe better. Helps out all the way around. I'm glad I had mine done! Balancing is a must. Makes them run real smooth and last longer especially the 292. Fuel injectioin is nice but Pricey and a lot of work. Won't get better mpgs than a good tuned carb will. A little better performance maybe. Not worth the big bucks to me. My Dad got just over 20 with his 292 3 speed at 55 when it was the speed limit, with no OD but hwy gears of some type. Unless your are going to do heavy hauling, I would go with a modest refined 250. It will work well for you. Love that purrr out the exhaust of the inline. H.