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Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

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post #1 of (permalink) Old 11-26-2007, 07:29 PM Thread Starter
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new guy w/ a new toy

Hey, my names jeff, Im from upstate NY (Amsterdam). SilentBob sent me this way cause there wasnt too much help on the hot rod forum for 4x4 jeeps, LOL
My background is in mostly older stuff (1930's). Ive been a machinist for 11yrs so that helps me keep my old junk on the the road. It also helps when its time to hot rod stuff!
Now why Im here, I just picked up a '90 YJ w/ a 4" rough country susp. lift, 3" body lift , 33x 12.5 tires (bridgestone dueler), 8.25 chrysler rear, stock front all w 3.55 gears (they were mismatched when I got it, 4.1 front/ 3.55 rear) It runs 2500rpm at 60mph so I decided to stay w/ the 3.55 (for now). The engine is a TPI 350 chivy w/ 350 tranny.
The guy that put it together was a total hacker and useless to ask any questions too. Maybe I shouldnt say hacker because they did put a ton-o-work into this thing, but they definetly took no pride in there work.
My biggest issue is tunning the TPI a little better. I was a little bummed when my first fillup only showed 11.3 mpg. I know this engine in its original vehicle got high 20's, so, besides the not having the overdrive tranny what gives?
Any one have any thoughts?
Stock GM computer, vehicle speed sensor, runs great, am I just expecting too much?
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post #2 of (permalink) Old 11-26-2007, 07:42 PM
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high 20's? as in MPG ??? with a V8? ....maybe on paper.....

theres a ton of chebby powered jeeps out there and i dont think i've ever heard of one getting "high 20's" for MPG.

if you are lucky, you might get right around 20....but i wouldnt ever expect more than 15 or 16 ...and even thats not as likely confgured as you describe

your biggest problem with jeeps is they have the aerodynamics of a cinder block......add bigger tires and now you crap for mileage!

I dont think you're going to get anything much better than that w/o dropping that lift off and maybe changnig your gears.

you will never see "high 20's" for MPG

a great place to start would be junking the body lift in my should be able to fit 33's with just the 4" suspenison lift......

Doesn't-have-a-Jeep'n Greg
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post #3 of (permalink) Old 11-26-2007, 07:44 PM
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Only thing I can add to the lack of overdrive is that you are driving a box. The areodynamics on these things are almost non existant. My 2.5 in a car got over 30 mpg I barely see 14.

Ya only go around once, best to enjoy it the first trip.
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post #4 of (permalink) Old 11-26-2007, 08:01 PM
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Tune? You want Tune, ditch the GM ECM and get a MegaSquirt Controller.
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post #5 of (permalink) Old 11-26-2007, 08:03 PM Thread Starter
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[QUOTE=JeepnGreg;1518323]high 20's? as in MPG ??? with a V8? ....maybe on paper.....
you will never see "high 20's" for MPG
OOps, not what I meant, Im not looking for high 20's for the jeep, LOL. But This setup in the vette or camaro easily do high 20's.
Im well aware of the arrow dynamics of the cinder block , Im just curious what things I could look into.
Ive been noticing bodylifts are kinda frowned upon, is that true?
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post #6 of (permalink) Old 11-26-2007, 09:01 PM
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Yes, body lifts fatique the metal around the tub mounts and destroy it. Then it raises the center of gravity, and of course, most Jeepers think it looks plain ugly. The reason people do it.. they think it's a cheap lift. There is no such thing as a cheap lift.
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post #7 of (permalink) Old 11-27-2007, 06:22 AM
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Welcome to the board! We're always glad to have another guy who can make his own stuff!

Pretty much what everyone else said. Your next step, if you haven't already done it, is make sure that the engine is running right and not throwing any codes. Then get the body set back down on the frame where it belongs.

After doing that, if you drive like there's a raw egg between your foot and the gas pedal and never exceed 50 MPH you should get into the mid-teens. Maybe even upper teens. Speed is the biggest killer of economy. Remember, aerodynamic drag increases with the square of speed - aerodynamic drag is 33% more at 60 than it is at 50, and in a Jeep aerodynamic drag is huge to begin with.

Final step for better mileage is to toss the Jeep body, put a Camaro body on, and lower it back down so the body is 4" off the pavement.

EVERYTHING's easy for the guy who doesn't have to do it.
B. Dash Fabrication
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post #8 of (permalink) Old 11-27-2007, 07:16 AM
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My new-to-me '99 TJ has gotten a best of 21 mpg. It's a Sahara, 4.0, 5 speed, AC, cruise, sound bar, etc. I commute 37 miles one way every day, 98% highway. Keeping it at 65, driving it as normally as I can, will get me 20-21 mpg. I had hoped for 23-24. I'm guessing the AC and cruise and all that stuff is adding a few hundred pounds which probably doesn't help.

OT - 1930's hotrods are very cool. Here's a shot of my '30 Model A coupe. Will be a flathead with a T-5, Ford Ranger rear end, front drop axle, Econoline spindles, split bones. And yes those are Jeep wheels on the rear. Will be 5-on-4.5 front and rear, steelies and bias plys. I'm going for a Traditional rod.

Attached Images
File Type: jpg car-side-small.jpg (95.4 KB, 2 views)

88YJ: Old, noisy, slow, and just generally wonderful. Wheeling Jeep.
04WJ: Less old, less noisy, less slow, daily driver Jeep.
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post #9 of (permalink) Old 11-27-2007, 02:48 PM Thread Starter
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I would love to post up a pic or two of the jeep but I already have my dinky winter tires on so we will have to wait for spring for that. Plus who knows, by spring I may have the camaro body on the chassis, LOL ,(Nope, I still have too many teeth for that)
Heres some pics from the toy box, hope you enjoy
'64 cutlass F-85 w/ 4 dellorto carbs

'51 plymouth cranbrook chopped 5" front and 6"s in the rear

'31 model A pickup 327 sbc, 4 rochesters, 5 speed, 4.11 gears, 2100lbs w/ me in it

'29 model A, stocker (but I love it that way too)

How bout late model bikes?
'79 yamaha xs650, I had $459 in her and traded it for the '29 coupe above!

My pride and joy, 1929 harley, last saw daylight in 1948, this was how she looked when I got her

5 months and 1/2 dozen ulcers later.

new project on the way, (me winching it outa theAdirondacks) '
'34 plymouth

I hope the pic show wasnt too far OT, but I guess this is still my introduction post.
Now back to the jeeps!
Do you think Im better off staying w. the 3.55's or should I go 4.1?
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post #10 of (permalink) Old 11-27-2007, 02:50 PM
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Nice Model that your Jag in the background as well?

Oh yea....gas mileage.....if you don't have an OBDII scanner, good time to get will tell you a lot about your what temp the engine is really running at....that has one of the most significant effects on gas can read the actual temp on the scanner and compare it to your temp would be surprised at how many people take out the t-stat thinking it will help cooling problems.

And....welcome to the board.

AKA DDawg16
84 CJ7, SOA, 5.7LTBI, 4L60E, 35"x12.5, 4.10 gears, F/Det, R/ARB, Full Roll Cage,
D44 Flat top in progress...
Link to my Frame up Restore
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