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post #1 of (permalink) Old 04-15-2001, 12:44 AM Thread Starter
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how do I get better MPG?

I just bought a '75 ScoutII and I'm looking to get the best fuel economy I can.It has a 345w/auto.I am wondering if I should buy a Jacobs ultra mileage master or MSD 6a or a Crane HI6? Which gives the best mileage for the money? Would it be worth the trouble to run cold air to the carb? What about running a large electric fan instead of the belt driven one? I've heard this wont keep it cool but I've got a new 4 core radiator in the scout.This Scout will be a daily driver with a little bit of offroading. Any good suggestions would help.Thanks.

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post #2 of (permalink) Old 04-15-2001, 01:52 PM
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Re: how do I get better MPG?

Poor fuel economy with these old V-8's is a problem! I can remember my brothers stock '78 (in 1980) with only around 25K original miles getting around 12 m.p.g.! He always swore by that old Scout and kept it for many years. He said ride was much better than a Jeep, it was a good tow platform, carried a pair of dog cages easily, and with a little work, able to show its ass to the "CJ's" on the trails. Back to the problem. Basic stuff first.

BASICS: Good for 1-2 extra MPG.
1) For road use, run high tire pressures, at least 30 PSI. Run a smaller radial tire on the road and swap for larger ones on trails.
2) Insure the brakes are in good order and do not drag.
3) Insure the bearings are in good order/repack. Insure trans/diff fluids are fresh. Run lower weight oil, 10W30 or less, no 20W50.
4) Drive slower, try to stay around 60 MPH or so! parasitic drag above 40 MPH hurts! Smooth throttle inputs.
5) Make sure all the original vacuum hoses, pollution device hoses, etc. are in good order.

SPECIFICS: Also good for an extra 1-2 MPG.
1) Since this is a daily driver, you need 3.54 or so gears, check the line sheet or rear diff tag to see what yours has.
2) The 4 sp. manual is a little more efficient. On the 727 auto, change the fluid/filter and insure it operates properly, firm shifts, no slippage
3) Install a high flow cat if originally fitted with a 70's vintage pellet varity that was prone to clogging. Install free flow exhaust.
4) Check the right side exhaust manifold for the butterfly valve assembly, and oil it and make sure it is operational (moves freely). If rusted shut this alone can cause the loss of a few MPG.

I am sure there are other tips, but this should get you started. I have yet to swap the ignition, but I am considering it. I do not think the electric fan is worth the effort, insure the stock clutch fan is in working order. Remember, this rig is built for years of toil, not great MPG! The old 345 is a durable mill that will run over 300K if properly maintained, that alone should be worth the loss of a few MPG! It has a factory forged crank, rod, pistons, and timing gears. My '79 with the 345 and 4sp. close ratio trans now gets 15 MPG on the road with these mods (It used to get 10 MPG or so). Recent 31" AT tires hurt a little, now 14 MPG, but they look great and work well off road. Scouts lead the way! Good luck!

Steve Mcqueen fan.
post #3 of (permalink) Old 04-15-2001, 02:46 PM
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Re: how do I get better MPG?

Get Holley Pro-Jection 4di! Jeep 360s get about 14-20 mpg with it!

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post #4 of (permalink) Old 04-16-2001, 05:29 PM
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Re: how do I get better MPG?

What kind of mileage do you get now that you need more?

I rebuilt my 345 - more compression, balanced, ported, cammed.. with a 2bbl Holley 350cfm carb, 4.09 gears, 33x12.50s, 4" lift, soft-top, 4spd.. I can squeeze 16mpg out of it if I stay at 65mph. 75mph and it becomes 10mpg.

I run a points distributor with a Pertronix Ignitor. NAPA OEM style coil, NAPA 7mm plug wires, Autolite 85 plugs.

I'm happy with my NAPA lifetime plug wires and stock type coil. The Pertronix is reliable, maintenance free, and easily field-fixed with spare points in the glovebox and a matchbook.

I'd spend the money on a ProJection closed loop setup before I bought into an MSD or Jacobs. I bought an Analog 2bbl setup, but the ECU is fried.. :-(

I have a clutched fan and 3-row high-efficiency radiator in mine - it keeps cool on the highway just fine, but on the trail it gets a bit too warm for my tastes. I'm going to put the clutch fan on my Travelall and go back to a fixed fan in the Scout. If I really notice the HP loss or extra road noise again (what, with a soft-top, rattling doors, the loud stereo, and tires?) I'll just drive the Scout onto the trailer and cruise in comfort in the 6mpg tow-Travelall.


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