Improving the gas mileage of the M-880 series

[maddawg308]

We all know the 318cid of the Dodge M880 series is a gas guzzler, a result of 1970s technology, but also of fulltime 4wd, locking hubs etc. Most owners of M880s get 12mpg on a REALLY good day, perhaps as low as 8 mpg on a bad day.

Was interested to hear any ideas you all have for increasing the gas mileage of this truck series, including repowering options. 318cid engines in today's trucks get much better mileage due to fuel injection, how hard would it be to add FI to an older -880?

 

[rizzo]

they make a partime kit for the t-case, that might help with locking hubs.

 

[98hd]

I'd do the part time kit first. Or you could do a doubler t-case setup. Use the front half of your 203 and an expensive adapter, then a 205 on the back of it. Lets you have a 4:1 low range.

Anyway, here is a link to TBI conversion http://ramchargercentral.com/index.php?action=howtoshow;id=88

TBI a nice RV style cam, headers and exhaust should help some.

 

[maddawg308]

So replacing the standard cast iron exhaust manifold with tubed headers would help it breathe? I thought in a single-pipe exhaust system, the muffler and catalytic are the limiting factor in the exhaust efficiency of the vehicle. Would replacing the stock carb help in getting the gas mileage to a better level? Or is the stock two-barrel the best for it now?

 

[98hd]

So replacing the standard cast iron exhaust manifold with tubed headers would help it breathe? I thought in a single-pipe exhaust system, the muffler and catalytic are the limiting factor in the exhaust efficiency of the vehicle. Would replacing the stock carb help in getting the gas mileage to a better level? Or is the stock two-barrel the best for it now?

Did the 880 come w/ a cat? I know my '75 w200 never had one. I would ditch the whole exhaust, and put in something that would breath better.

 

[Bob H]

While I'm sure there are a few things that can be done to improve the fuel mileage.

but these things weigh well over 4000lbs, have the aerodynamics of a brick and 4.10 gearing. They could never get good mileage.

I firmly believe that a small 4 barrel & a RV cam would help out. I think headers would be counter productive on these trucks as it takes low end torque to get these heavy sob's rolling.