258 TBI Swap Question-EZ - JeepForum.com
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post #1 of 7 Old 05-16-2011, 06:49 AM Thread Starter
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258 TBI Swap Question-EZ

I have an 81 Jeep that I really don't use much. It has had alot of work done to it and money spent by the PO, and in the big picture it is quite solid.

Here is the set-up:

SPOA, Dana 44's, 37" tires, 4.10's and a T-176.

I have driven it very little because truthfully, it has not ran real great since I got it. Good, but never as good as I would like, that and it is hard on gas I guess since I live so far from anywhere.

With 33's in the summer and no top-around 14 MPG, but no more than that.

With 37's and a horrible headwind / rain / snow and sleet I got 12.5 MPG

Here is my question:

Assuming I do a homebrew TBI swap (picture running 4.3 rig in my yard) and do it simply while doing the Team Rush upgrade, about what type of mileage improvement should I see?

I know there is a TBI post that is 32 pages long, but I am mainly interested in people's thoughts on mileage and if it was worth it. The tech stuff will come later when I get closer.

If I could knock down 14-15 MPG daily (all conditions) I would be happy. I am most likely going to run a 35" milder tread tire for 3 season use, and save the big tires for winter.

Oh, and please spare me the "it's a Jeep, buy a Honda to drive daily" stuff...I know, I know!!!

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post #2 of 7 Old 05-16-2011, 04:18 PM
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1981 CJ8 
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My tire size and other specs are off of yours, but after a couple tanks of gas, I am averaging about 15mpg in a CJ8 with 31" tires, unknown gears, a 258 and aftermarket intake/exhaust set-up. That is about what I got, no more, than with a freshly rebuilt MC2150. In my limited experience, a freshly rebuilt TBI from Howell did no better than a freshly rebuilt motorcraft carburetor, but it did allow me to pass emissions inspection, and that was my goal.
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post #3 of 7 Old 05-16-2011, 05:19 PM
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1986 CJ7 
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yeah you are getting pretty good MPG as is. Junkyard TBI usually nets around 14 MPG from what I have read depending on tire size and weight though. I just finished my TBI project and it does run a whole lot better than the BBD carb, fires right up and no more rough idle. I'm running the off-road version though because there are no emissions requirements in KY.
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post #4 of 7 Old 05-17-2011, 06:16 AM Thread Starter
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OK that helps. It sounds like I must have been fairly close on the tune with the other carbs.

I have a 2100 on it now. It idles fine, but has some dead spots and dies on occasion etc. I am looking into that later this week.

Here is the big picture. I am tired of not driving it. The PO spent 6K on the mechanicals and then I bought it and remodeled the Jeep. It does everything well except run as good as I would like.

If it ran great, I would likely drive it during the winter 3-4 times a week and about the same in summer. I was going to get a stocker Jeep, but I know myself, and I would be right back where I am soon.....

I think I am going to give the 2100 some time and get it to cooperate. If I don't get too far there, I will look into the TBI. I have a lead on a complete running truck.

Thank you freinds. I appreciate your help.

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post #5 of 7 Old 05-17-2011, 06:23 AM
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1980 CJ5 
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Read all the reviews regarding TBI. I fought through three different carbs before throwing in the towel and installing a TBI system. Wish I had years ago.
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post #6 of 7 Old 05-17-2011, 06:31 AM Thread Starter
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I have had many Jeeps. One that I drove daily with 38's for ten years, and few milder ones etc. and overall this is the best one I have had. Enough power to drive down the road fine with a rebuild and a cam/ header. Steers, stops great and it literally drives so well that my pal's wife "stole it" and drove it about 5 miles in busy traffic at 60 mph. I didn't even give her the "lesson" that we have to give people. She said it drove fine.

I don't mind a little cold-blooded in the morning or whatever. But after I spent about 3 weeks in Weber Hell, and have now crossed over to 2100 issues I am beginning to look at other methods of metering fuel.

I have never had this many fuel related issues in all of my years of cars and trucks......

Continuing to read here on the TBI.

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post #7 of 7 Old 05-17-2011, 07:59 AM
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1982 CJ7 
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Location: Boise
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x2 on the TBI swap. Did mine using a junkyard donor (no need for the Howell "fuel only" kit) and added ALL the sensors including knock, VSS, etc. and locked down the dizzy to let the computer control the spark. Runs like a modern car (even when cold).

With a cam and headers, you'll probably need to program a new chip for the ECU due to the fuel needs. My 258 is stock and I run the GM 4.3L chip from the V6 truck donor I pulled from.
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