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post #1 of (permalink) Old 03-21-2000, 08:17 PM
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CJ 258 top end

Hello all,

I have an 85 CJ8 with a rebuilt 258, Weber carb and TFI ignition. I drive my CJ daily and
can only attain about 65 - 70 mph on the highway. I have a stock T176, 4.10 ratio and
35" tires.

Is this top end all I should expect out of it, or can I get a little more with what I have? The
timing was OK last time it was checked and the engine doesn't ping or knock during

Any comments or ideas would be appreciated.


85 CJ8
"Put some tire tracks in the sands of time"
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post #2 of (permalink) Old 03-21-2000, 08:34 PM
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Re: CJ 258 top end

George I don't think you will find too many people here that could drive 70 mph [img]/wwwthreads_images/icons/wink.gif[/img] let alone even try to even get close too that speed.[img]/wwwthreads_images/icons/tongue.gif[/img]
We're gonna hafta start callin you "speedy".[img]/wwwthreads_images/icons/smile.gif[/img]

"No officer I haven't been drinking , Thats just how my Jeep drives"
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post #3 of (permalink) Old 03-21-2000, 08:58 PM
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Re: CJ 258 top end

Do you have a tachometer? What kind of revs are you turning at 60-70mph ...I'm figuring 2700-2800 with the specs on tires & gears you listed. -Anyways that is where it just starts delivering the ponies right? I'm no expert on the ole I6, but I know that mine likes to sit at about 2400-2600 running on the highway turning 31s with 3.31gears and it delivers just enough to stay at speed up these long hills in the Carolinas. Now that TFI and ignition upgrade will help you get a good burn out of her but I don't know about getting many more ponies out of her after that for the highway. I guess it depends on what kind of rpms you are comfortable running at, mine will sing to 3800 ...but she makes me ease up for fear of throwing a rod or loosing a valve - so I rarely take it past 3300. (Not to mention that after about 85mph, she feels more like a watercraft than a Jeep) Anyways, just thought I'd give you my ideas. Later.

'84 CJ7 258 w/HEI

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post #4 of (permalink) Old 03-21-2000, 09:08 PM
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Re: CJ 258 top end

My CJ7 258 4.0 head shaved, ported & polished with oversized values, jacobs ignition, header & weber will only do 85 with a major tail wind down hill. On an uphill climb-it will still slow down to 65-70. Right now it is sleeping... its 999 went bye bye.

Mindbender 85CJ7 I258 [img]/wwwthreads_images/icons/smile.gif[/img] 40 head ported polished [img]/wwwthreads_images/icons/smile.gif[/img]
Jacobs [img]/wwwthreads_images/icons/smile.gif[/img] 31" [img]/wwwthreads_images/icons/smile.gif[/img] 999
post #5 of (permalink) Old 03-22-2000, 02:30 PM
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Re: CJ 258 top end

George, my 86CJ7 with the 258 I6, MPI kit, 4.88 gears, NV4500, and 32X11.50 BFG MT's has been up to 80mph with plenty still
left on a level road. BTW, I seldom go that fast because after all it is a Jeep, not a sportscar.

post #6 of (permalink) Old 03-22-2000, 06:38 PM
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Re: CJ 258 top end

Who here is sure that their speedo is accurate? Most everybody has oversized tires that didn't come on their Jeep. Others have changed gear ratios. I'm pretty much happy just bouncing along keeping up with traffic and not being passed up by Geo's and other various econo-boxes. I recently was tooling along at about 65 and I looked at my tach and it was near 4000. I suddenly realized it was still in 3rd gear!!!!! My 258 was really buzzing. With all the wind noise and canvas flapping you couldn't hear the engine very well. I guess that comes from driving all those 5 speed cars the past few years with 5th gear up and to the right.

Point is, CJ's are not practical at high speeds. A highway trip to me is a real adventure.

Loose nut behind the wheel
Another right-wing conservative.....
Born and raised in Jeep-Town
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