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-   -   How would you rebuild this 258? (http://www.jeepforum.com/forum/f8/how-would-you-rebuild-258-a-1372082/)

jduress 05-22-2012 02:25 PM

How would you rebuild this 258?
 
I am swapping a 258 in my 85 cj 7 to get rid of the 4 cylinder, I was just wanting some input on how you guys would go about rebuilding the 258, its a complete motor out of a 79 cj5. The odometer reads 60,000 and some (correct) miles but it has been sitting since 1997. I am probably going with a carb as I am in college and do not have the money and time for an efi 4.0 head swap. So I wanted to see what you guys have done and what you think on issues like: What carb and intake to use? How far into the motor should I go? Easy and inexpensive upgrades that can be done? Exhaust? Thanks!

BioTex 05-22-2012 03:28 PM

If it were me, I would save my money, and run stock (OEM) intake and exhaust. The 258 is a low rpm workhorse. You very well could slightly decrease your HP running a cheap header that will rust out after a couple years anyways.

If it were me, I would save for TBI or EFI. A junkyard TBI can be built for a hundred bucks or maybe a little more depending on the adapter.

As for the engine, prime the pump, and run a compression check and go from there. Read the plugs while you are at it...

only in a jeep cj 05-22-2012 04:33 PM

"Low on time and money" .....If the engine runs, swap it in AS IS and keep it all stock. Run it for a while until it needs a rebuild. Now here's what I would do (and DID). It cost the same to rebuild a 4.2 as it does a 4.0 as far as rebuild kits and labor cost. So while it is running fine for now, keep your eyes open for a low buck or free 4.0 that needs a rebuild. The crank and rods in your 79 are the more desirable 12 counterweight version that folks want for the stroker builds. So when the time comes, bring your 4.2 crank and rods with the 4.0 block/head etc to the re builder and do it once. Since it will be a major task to remove the engine and all, doing the harness splice and other fuel injection parts at the same time won't be as bad.

jduress 05-22-2012 07:32 PM

I have not tried to start the motor yet, it is still in the cj 5, I have turned it over by hand its not locked up, I was thinking about running a motorcraft carb, have been reading alot of good things about them

Mickey_Mouse 05-23-2012 03:15 AM

new cam+hei distributor, 60,000 miles? Still a good running motor. Chec for exhaust leaks from the exhaust manifold back to the catalytic conveter to the muffler and back. I would run the motor without rebuliding but adding upgrades like the HEI distributor and carb. motorcraft 2100 electric.


http://www.ebay.com/itm/NEW-MotorCra...d26304&vxp=mtr

this guy is who I bought my carb off of. kit comes with a cd/instruction manual with different variations installing.


if you buy a Offenhauser intake: http://www.summitracing.com/parts/OFY-5416: you could install a holly 650 CFM carb. Changes the intake to 4 barrel.

some Jeepers have installed TBI on their Jeeps.

jduress 05-23-2012 09:01 AM

I like the looks of his kits, I sent him a message asking questions about my particular setup, Which brand of distributor and cam would you recommend?

prew32 08-08-2012 06:31 PM

Quote:

Originally Posted by Mickey_Mouse (Post 13611247)
new cam+hei distributor, 60,000 miles? Still a good running motor. Chec for exhaust leaks from the exhaust manifold back to the catalytic conveter to the muffler and back. I would run the motor without rebuliding but adding upgrades like the HEI distributor and carb. motorcraft 2100 electric.


http://www.ebay.com/itm/NEW-MotorCra...d26304&vxp=mtr

this guy is who I bought my carb off of. kit comes with a cd/instruction manual with different variations installing.


if you buy a Offenhauser intake: http://www.summitracing.com/parts/OFY-5416: you could install a holly 650 CFM carb. Changes the intake to 4 barrel.

some Jeepers have installed TBI on their Jeeps.


Is anyone else running one of these carbs?? Debating on whether or not do a howell fuel injection or just switch to a better carb, I just did the team rush upgrade and my 258 still isnt running quite right

aggiejon 08-09-2012 07:14 AM

I swapped in a motorcraft 2100 carb and HEI. Ran well. My motor was pretty wore out. Found a deal on a parts jeep with a fresh drivetrain.

Watched Craigslist and swapped the motor and did a junkyard mpfi. Thanks to Craigslist, eBay, some patience and searching, and the scrapyard, did the whole thing for nearly even money.

Was a daunting task, especially pareing down a harness, but was worth it now that it starts on the third spin and idles like a top. So smooth it's like silk.

My opinion, swap it in and run it. Make upgrades as you have funds. Get it running and driving. It is more enjoyable that way. Everyone wants to go for a ride, not look at it in the garage.

twinstickd20 08-09-2012 08:56 AM

2 Attachment(s)
Quote:

Originally Posted by aggiejon
Everyone wants to go for a ride, not look at it in the garage.

I know that feeling, it's been down for a month. Now waiting to hear back from the machine shop.

baldfatdad 08-09-2012 10:12 AM

I'd do a compression test on the motor. You won't get real good numbers with it cold and turning it by hand, but you will see if anything is real bad, if you come up with a cylinder with no compression. If it passes that: I'd change the valve cover gasket. A lot easier when its out of the vehicle. Maybe the valve cover, if the old one is warped or cracked. Rebuild the carb. I've run a BBD for 20 years, no problems. Just follow the instructions in the kit in order and exactly. New plugs, wires, cap and rotor. Run it.
Then read, learn, decide what you want to do with the jeep and build the engine to do that. I rock crawl, my engine hardly ever sees 2k. My buddy runs mud, his idles higher than that (that's a joke), and runs to 5k. They both are built for what they do.


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