How to improve MPG of LDS 465 1A engine

[Andrews CC]

I have a 1967 Deuce with a 1986 rebuilt Continental LDS 465 1A engine with the FDC bypassed. It had lots of power but only 5.5 MPG efficiency and a lot of black smoke.

After reading all the threads on the subject, ( thank you all and this forum! ) I installed an exhaust temperature gauge and found it running way hot at 1400 degrees. so turned it down two full turns (from five threads sticking out of second nut down to three). (It is now three flats out from where it will not start). Now it runs at 1000 degrees and I need to use 3rd gear on a steep grade. It runs 55 MPH on the flat, and smokes much less. so I can live with that, but i am still only getting 7.5 MPG.

I am going to Alaska, and would like to improve the mileage. Most of the threads talk about 10MPG but that is probably with a LDT.

Is 7.5 what I should be getting with this higher HP engine and my load?

Head gasket is leaking a little oil at front, what other damage did running it too hot all those years probably cause? I don't want a failure in the middle of the tundra. Besides a head gasket, what extra parts should I take?


Other details:
Running new diesel,
I have never been able to get over 8 PSI boost.
It has a LDT D turbo
Tried to turn down the droop screw, but just a quarter turn in and it would not start. so put it back where it was.
11:00 duel tires with one rear drive axle out.
Total weight is 22,000 pounds, full tarp, plus am towing a jeep
Engine has label of rebuilt LDS 465 1A, but has the bell housing and pan of an LDT.???? how weird is that??
US Army gave to fire department, sold to guy I bought it from.
Fuel adjustment had wire seal still on it from rebuild factory. so it has been running hot for years, probably since the military bypassed the FDC and put the yellow label on the engine saying "FDC bypassed, use diesel only"
Running Rotellia oil and Lukis additive at 50 to 60 PSI


Thanks

Curt

 

[crazywelder72]

Is your ETG installed before or after the turbo?
I don't have any advice about the mileage but i will be curious to read along.

 

[m-35tom]

what load are you carrying? are you running on flat and level roads? at 55 mph you are not going to set any records on mpg. try at 40 and see a big differance. the best you can hope for will be at about 1900 rpm, any higher and mpg will go down. fuel = hp = moving x weight at x speed. diesel is diesel and i doubt you will see any mpg differance between ldt and lds at steady mph, just slightly more hp

tom

 

[Flyingvan911]

I get about 8.5 or so with the fuel screw set where the SD National Guard/Toole Depot had it. (I also have an LDS.) I plan to install a pyro sometime. The pistons are cooled by the motor oil spraying up on the bottom of the piston. I'm no expert on it so I'm not sure how much higher the EGT's can safely go above a LDT (without the oil jets).

 

[condor418]

from what i have read about the lds swap is 1 flip the oil pan around for clearance issues. 2 use the bellhousing from the 2.5 ton because the starter is on the oposite side on a 5 ton and wouldnt clear the turbo. as for mpg i have no clue good luck

 

[Recovry4x4]

As Tom said, slow down or toss it on a stretcher. Can also reduce rolling resistance.

 

[gimpyrobb]

If you have access to the LDS troubleshooting guide, it has a fuel use per hour grid in it that shows how much fuel per RPM you will use. I would compare your numbers to that to see if you are in the right ballpark.

 

[ken]

Like everyone else said slow down. Driving a M35 at 55 it's max speed is like driving a civi car at 100. It's going to get poor milage at that speed. It will get it's best milage/power at 1800 to 2000 RPM's. Next air all the tires up to the max pressure. This wont make much difference on a small car. But with 22K LBS the less rolling resitance the better. Make sure the TOE IN on the front axle is between 3/16 and 1/4 inch. I've seen alot of the trucks with too much toe in. Making the front tires scrub constantly. Then install some lockout hubs or deslpine some. This will stop the front axle from turning if you have a airshift Tcase. Not turning that front axle gave me 1 1/2 MPG.

 

[maddawg308]

You're not going to set mileage records in a military truck regardless of what you do to it. But you can fuel it with half diesel and half free used motor oil, thereby halving the cost of fuel in the tank. In a way you are doubling the mileage for the fuel you pay for. It's just another way of looking at it, but it made me feel better when I was tanking up the deuce.

 

[m816]

I don't know what damage running 1400 did to your engine, But I ran mine at that temp and first thing that let go was the govenor in the IP and then # three piston got a hole the size of my little pinky burned through it and aluminum melted all over the main bearings and completely wiped the cylinder all to the tune of about two grand in parts. We now run a pyro on it and keep the temps under 1200 max. At 1400 aluminum melts and it doesn't make any diference how much oil splashes on the piston skirt, it is gonna melt.

 

[rrrr]

Like everyone else said slow down. Driving a M35 at 55 it's max speed is like driving a civi car at 100. It's going to get poor milage at that speed. It will get it's best milage/power at 1800 to 2000 RPM's. Next air all the tires up to the max pressure. This wont make much difference on a small car. But with 22K LBS the less rolling resitance the better. Make sure the TOE IN on the front axle is between 3/16 and 1/4 inch. I've seen alot of the trucks with too much toe in. Making the front tires scrub constantly. Then install some lockout hubs or deslpine some. This will stop the front axle from turning if you have a airshift Tcase. Not turning that front axle gave me 1 1/2 MPG.

This is what I would do as well. Very good advice.

 

[Floridianson]

How are you loading the motor to produce boost?

 

[Floridianson]

The reason I ask is trying to produce boost while on the road is not the correct way to check. I would do like the tm calls for by holding the brakes and have someone else record the boost numbers. I would also do it twice to conferm the numbers. You should be around 4/5lb at 1600rpm and 10lb at 2100. Do the main fuel first then do the droop.

 

[M813A1]

I simple trick that will help a little is to air up your tires to the highway speed rating on the data plate and that will uncrease the diameter just a it and help your spped and milegae just a bit !!

 

[Recovry4x4]

I was told over the weekend at the Aberdeen MV show that since I have lockout hubs on front. Remove my front rear axle shafts and bolt my old front flange's on the middle axle. They said it makes the Deuce easier to drive and less tire scrubbing. It would have to help with fuel consumption too. Jim

This is true for the most part. Without getting into a whole bunch of (hard for me) explanation, you only need to remove one shaft on that fwd rear axle to net the gain. Max tire inflation always helps as does proper alignment. If you would rather run with all the shafts in the back then you need to match and pair up your tires correctly. Assign each tire a letter associated with the curcumference. Letter A would be for the tire with the greatest circumference and letter H for the tire with the least. Get them all situated by size, greatest to least, and pair them up this way. Tires A+B on one side and G + H on the other side of one axle, tires C + D and E + F paired and on the second axle.
There is no other way to match the output of each axle any closer except by adjusting tire circumference.

 

[gimpyrobb]

Well, that AND the fact it is not good for your transmission.

http://www.steelsoldiers.com/deuce/38371-deuce-transmission-disaster-pics.html

 

[EMD567]

Two things- Get your foot out of it, and change to radial tires. Radial tires have less rolling resistance, and as such, run cooler.
Another trick, and while quite hard in the deuce, is to get into the highest gear you can, as soon as you can. If you are starting at the top of a hill, use gravity, and short shift.

 

[greg2560]

Humm funny no one said check the air filter... Got to have air

 

[jesusgatos]

Not turning that front axle gave me 1 1/2 MPG.

wow

 

[hilber]

Interesting examples. I have a non turbo deuce and I averaged 5 mpg from Redstone to Homer, GA. (65 miles Northeast of Atl.). Bought a deuce with a turbo at Ft. Campbell. Filled it up before I left. 240 miles later it took 24 gallons. I ran it hard all the way and was actually passing some trucks coming across the mountains in Tennessee headed to GA. I filled it when I got off I-85 and headed home and averaged 10 mpg again. It would only run 55 but I didn't have to downshift on every steep hill like in the non turbo. Best i recall only a hand full of downshifts and the non turbo would drop to 15 mph on some hills around Chattanooga.