I have a 87' F-350 4X4 dump, 460 and a C4 auto trans. The light weight is 8500# and I'm getting 5 to 6 miles per gallon. I've since changed the Holley carb to a Edlebrock with no change to the economy, is this what I can expect or is something wrong?

Thanks in advance...
Tony

 

I think that is about you are going to get with that big truck.I get 7-9 miles with my 1995 f 250.

 

Two things against any decent mileage here, 460 CID doesn't help, but the weight of the truck is one and I will bet it has a low rear end ratio (high numerically) is two. My '84 F250 superduty, suercab with 4.10's is up to 9+ mpg after exhaust, dist. and mods tothe stock carb (soon to be replaced).

 

Thanks for the replies...What distributor did you use? On the exhaust, did you go with duals?


Tony

 

I get 8-10 highway, 4-6 around town on my '83 F350 (10,000 GVWR) flatbed dump with 460, C6, 4.10, and A/C after rebuilding the stock Holley 4180C-4V carburetor. Previous owner had really screwed up the carb including messing up the choke, drilling out the main jets and installing the wrong power valve. Holley has a really good technical service on-line; I gave them my part # and list # (taken directly from the carburetor casting) and they replied with the proper jet # and power valve #. All the emission systems are stock and operational. My base timing is 10 BTDC rather than 8 BTDC as called for on the sticker. The proper power valve for your specific vehicle is very important for optimum gas mileage; those that come with the rebuild kits are generally "one-size-fits-all". Piffery1

 

Went with 2 1/2 badck to the muffler, which is 3" and 3" tailpipe. I still have the stock dist. I changed the advance curve from the 18 degrees in the dist, 36 degrees on the crank to the 13 degree dist curve and 26 degrees on the crank. Bumped initial timing from 6 to 8 degrees and put another light spring on the advance weights after removing the heavy one, but made the second one fairly tight. Total advance at 34 degrees in by 3500 rpm. The vacuum unit stayed stock and connects to ported vacuum on carb. No ping on regular and picked up almost 1 1/2mpg. The exhaust gave me 2 mpg.