Off Roading Forums banner

question on rebuilding 258

3978 Views 6 Replies 2 Participants Last post by  **DONOTDELETE**
I am getting ready to rebuild a 84 258 engine for my jeep. i am writing to look for help on what parts i should use and also how to make it a little more powerful, i have the engine out. i am going to put a weber carb on it and dual exhaust, but any other suggestions would be great. Thanks, Pat

1 - 7 of 7 Posts
I ran a Holley 390 cfm 4bbl with an Offenhauser intake for a while, did pretty good. Only reason I took it
off was because I swapped to a 305 TPI.

I have considered doing the 4 bbl swap on my 87 258 as well. All emissions are stripped and I need more power. I was looking into a Clifford performance 4 bbl intake and holley 390 cfm, plus a header and cam. What is the power increase and gas milage like with the 4 bbl? Also, what about the coolant lines that run into the intake, and the vaccum actuator for the heater console?

1987 YJ Laredo
Rylan D.
You ask a real interesting question. Wanting a little more power can be an addiction and lead to wanting more and more. Rather than spend thousands of dollars, just drop a V8 in it. The cost will probably be less that what it would cost you to build up your system. For example:
Competition Cam - $140
Springs, Retainers, etc - $150
4.0 head for replacement - $100.00
used value cover-$40.00
Significant head work and values - $500.00 (stainless steel values, 2.02 & 1.75, harded seats and retainers, brass guides, .060 off the head, polished and ported/matched to exhaust.
New Rods, Pistons, Rings - $225.00 for forged pistons add $125.00
Boring of the engine - $50-75
Weber Carb - $350, Holley carb - $250, New intake manifold - $150-175
Jacobs Electronics - $200-$300
Headers - $200.00
Mechanic charge,unless you do it. $750.00
That is -- unless you just want to see what a I6 will do or you know precisely what you want to do with the jeep and then can adjust it to fit what you want. Peace.

CJ7 258
See less See more
I rebuilt my 258 a year ago, it ran great.......then the block cracked with about 1000 miles on it.......fought with the rebuilder to fix or replace (no luck)

Do yourself a favor and put a 304/360 in it.....I bought a donor Wagoneer for a grand, pulled the engine and slapped in my CJ.....runs great and I have gobs more power!! I6's have there pros/cons but you cant beat the extra cubic $.02

Go to my Jeep site and read Tim Weaver's articles and take a look a some of the things I did to mine.
Both Clifford Performance and
HESCO are good sources for upgraded components.
I like Badger brand pistons (from NAPA)
A heavy duty (not hi-volume) oil pump is a good idea.
Tell the cam shaft vendor what you will be using your Jeep mostly for, etc.
A 1991 4.0 head (see Tim's article) and Webber/HEI or an MPI will top it off nicely.
Have fun!



See less See more

Check out this post . I think there is alot of good information here
even for a jeep motor. It has been said that this guys I-6 idles like it is stock motor.
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.