I'm courious if there is anything else I can do to improve the gas mileage a little. I just got back 2 days ago with my new (old) 66 f-250 CS and got 9 mpg avg comming from MN to WA. When I got back I installed my Tanuou (however it is spelled) and had to make a long trip in WA. 11.76 MPG was the best I got.

I was thinking the carb may need to be jetted to accomadate the higher altitude but I'm not so sure any more. I bought the truck in MN elv 1,368 and where I live in WA it is 1,952. Is that elevation going to affect the fuel mix in any significant way. I think the rule of thumb is 2 jet sizes per 1500 ft.

If it will not really affect it I guess the only way to get more miles would be to put the 2bbl carb and manifold back on, and remove the performance cam. But the truck is too much fun to drive to revert back to stock stuff. The engine has been upgraded to electronic ignition also.

Would adding headers have a small effect on the mialage?

Thanks,

 

Are you sure you've got the right jets in the carburetor to begin with? You might drop a few sizes and see what happens.

Adding headers would affect mileage for sure! Figure about 2-3mpg gain.

Something else you can do is play with the timing. Advance it a couple degrees at a time until it starts to ping, then back it off 3 or 4 degrees.

 

To my knowledge the jets have not been touched since the carb was installed 2 years ago. It is a edelbrock thunder AVS 650 manual choke.

Is there a company that makes headers for the Camper Special? I was told headers are made for the engine but the passenger side would have issues because of the suspension on the camper special models.

 

Other forum members are happy with Hooker or Headman headers, to name a few. You could look thru the wrecking yards to find a truck similar year as yours, but not the CS, see if there is really any difference. I had to modify my Dynomax headers to clear the starter, it was no big deal for the muffler shop to bend and fit some pipe to reroute the header pipe. Maybe thats all you'd need. My Dynomax has 2 pipes that reach in front of the frame crossmember and slip into the rest of the pipes near the collector, there is a constant exhaust leak. I'm going to buy headman next.
I have a Edel 650 AVS on my 416, I'm at 5000 feet and made several changes to the jets and rods. I'm running 8% lean on primaries and 2-4% lean on secondaries. Make sure your pcv valve is cleaned with Gumout carb spray. Everyone says the exhaust is the big restriction in the FE trucks, so headers should help, but they are a hassle at times too. Make sure to run dual exhaust down stream of the headers, and make sure they flare the pipe to fit the header reducer that bolts to the end of the collector. My muffler shop just stuck the exhaust pipe in the reducer and welded it in. I know theres a big flow restriction there that I need to correct. I'm also told to stop the exhaust pipes ahead of the rear tires for less backpressure. Good luck and happy cruisin.

 

I'm thinking this is the origin of the bad gas mileage. That fun costs money! (of course, it's worth it)
jor

 

You bet it costs money its really hard to force myself to try and be consertavite accelcerating around town. But with all those ponies under the hood you can't help yourself every now and then. Plus it gives me a chance to get back at all the neighbors who wake my 7 month up at all hours of the evening and night. The duel glass packs really make some good noise