Gentlemen,
Replaced many items on my slant, trying to regain some type of reasonable gas mileage. Runs very well, I do have the lean-burn air-box type of computer with a double pick-up type distributor and thought this might be the problem, seeing speed picks up slowly. Top speed seems reasonable for a heavy pick-up, around 70-75 MPH, but mileage is 14 MPG at best. I found replacement computers for about 135 bucks and distributors for about 55, what do you think? Items replaced :exhaust manifold, carburator (new 1945 Holley, not rebuilt), timing chain set, gas pump, water pump, etc.

Where are you located and what kind of emission tests do you have to pass? Is your '87 equipped with an oxygen sensor?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

No, it doesn't have an O2 sensor. I'm in NJ, fairly strict emissions, so that's why I thought it might be wise to go this route, instead of the HEI route. One of you moderators said something that stuck, "If it worked for almost 20 years, maybe it's worth sticking with".

...so, where are you located, and what kind of emission tests do you have to pass?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I am going through the same battle you are right now. I have a 1986 Dodge ram van with a 225 and the california emissions package. First i dumped the leanburn/spark control computer in favor of the HEI and went to a Carter BBD on a two barrel intake. My gas mileage went from about 9 MPG to 5 MPG. I am about to try reinstalling the computer and a computer controlled two barrel, and may try hooking the spark control computer back up if the lean burn goes well.

I would check all of your sensors as well as all of the vacuum hoses. If your truck is like mine was, you have those little hard plastic hoses rather than proper ruber hoses. These crack and break, esopecially after 20 years. Another item to check is the vacuum pod on the computer. I discovered that mine was blown after I had pulled the computer. The vacuum pod on the computer controls the timing and may also be involved in determining proper fuel mixture for the carb (I am still investigating this possibility). A shop manual for your truck is a MUST if you are diagnosing your lean burn system.

Keep in mind that the factory rated these vehicles at 15 MPG when new, so your 14 MPG isn't too far off the mark. Remember, these aren't little 2500 pound A-bodies. Trucks and vans are HEAVY and have the aerodynamics of a brick.

Thanks Reed,
I figured that mileage was close, but just looking at the size of my stinky little 1-barrel carb., where is all that gas going? Another thread suggested checking the gaps of the pick-ups, which I'll try, or like you said, with 130K, maybe that's the best I'm going to get.

Your gas mileage will depend alot on your gearing. I have an automatic tranny and 3.54 rear gears. Great for off the line but I cruise at 50 MPH on the highway and turn 3000 RPM to do it.

You may want to try swapping to a two barrel carb and run an early 80s Carter BBD or Holley 6280 feedback carb. This would give you more power but would also keep the lean burn. That is what I am going to try as soon as I get my vacuum pod fixed on my computer. The two barrel carb would help with power and therefore you might get better MPG since you would open the throttle less.

Another place to look is your EGR valve. By the late 80s the EGR valve had developed into an integral part of the engine management systems. I know that the EGR valve will have an effect on both timing and mileage, so make sure yours is functioning properly. I may actually hook mine back up...

You shouldn't be so upset about getting 14 MPG in your truck, that's better than what I get with my Dart.

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1973 Dart Swinger Super 6 with 71k
1976 Datsun 280ZX with Mopar I-6

Swinglo- a 73 swinger with a one barrel should do better than 14MPG. Sounds like you need to check your vacuum lines, carb condition, valve lash, and timing.

my 82 D150 will do at least 90mph. i am getting about 18mpg right now. i hope to ruin that with a set of 4.10 gears soon, but it'll allow me to pull down a house.


btw, this didn't happen until i killed my lean burn system.

sb

What is your current setup? What sort of gears are you running (auto or manual?)?

Before I blowed mine up!
I would get 19.28 on the open road - at 65 mph
Close to the tear down. I think I was getting around 14 in and around town that is - stayed away from the highways as it was not running where I felt safe taking it out on the big roads! LOL

Sounds like I might have had a good motor before - and you gotta remember that this is in one of those bricks that Reed mentions!!

I can't wait to see what the new motor does - I hope to heck I don't have to find out how big my fuel tank is every time I drive it now!

Later,
Dan

i've got 3.21s in the rear end, 215/75-15s for tires, and an 833OD. i'm constantly having to downshift to 3rd out on the hwy, and any load at all kills it...so 4.10s it is.

later i may do some hot rod stuff to it, but NOT til i finish my B'cuda.

sb

Are you still running a one barrel carb? Simply swapping to a two barrel might alleviate you power loss. Much cheaper and easier than a gear swap!

On a side note, I scored an original condition Super Six BBD last weekend at the boneyard. I swapped it onto my van and initial driving results seem to indicate that my gas mileage has tripled. I need to drive it more to be sure, but my gas guage hasn't moved since Sunday night and I have been driving it every day this week. Woo hoo!

actually, mine has the 2bbl already.

overpasses, long uphills and that sort of thing is when i have to downshift to stay with traffic.

i want to run bigger tires (the 215s just look puny on that thing) also for a little ground clearance during hunting season. i already have to really use a lot of pedal to get it rolling, so gears are going in....i already have em and the install kit.

sb