258 Rebuild and Mods

[gimmesomerocks]

So, I am looking for some advice, pics, gerneral information about additions everyone has made to their 258. I want to put dual outlet headers and a four barrel intake and carb, HEI kit, but that is the end of my thought process..... I want a rough cam, but not too rough, pretty much just want that rough idle, and then something that will give the engine the performance it needs for trail riding, crawling around, and some light street driving. Are there any other mods that I should do for the motor? I plan on just doing a light rebuild, not messing with the compression, replacing the tired bearings with stock size replacements, and a good cleaning, new gaskets, and a nice break-in smile -- hopefully......

[hole]

If your budget allows MPI is a pretty nice way to go.

[gimmesomerocks]

no injection, way over budget....just HEI ignition is about as high tech as this CJ will see

[Lawless_Jeep]

I had my 258 bored .030 over, so now it's a 262 instead of a 258. It's balanced, blueprinted, and the heaviest crank available was used. I'm running hypereurectic pistons, and a Erson 280 cam. The head is ported and larger valves were installed, and topped with Harland Sharp roller rockers. It's also decked to where I'm running a 9.8:1 compression. A Clifford dual outlet header, y-piped into a single exhaust exits the gas, while I have a Clifford intake topped with the Holley 390cfm. I have TeamRushed the distributor cap/wires/plugs, while a MSD 6AL and MSD Blaster 2 coil keep everything fired.
I love everything except the cam. The cam is more of a higher rpm cam, which I rarely use. It has a very nice "thump, thump, thump" to it though. I'm planning on switching to a smaller lift cam from Comp Cams. I'm looking at their 260H cam. You can download their free Camp Quest program and input your engines' data to see which cam best suits you. With my engine specs, and the 260H, it claims I'll be around 255 hp and 311 tq. I believe I'm a bit over that now, but it doesn't come in until late in the rpm range. It's great for highway and interestate running.
You'll want to tune the Holley. I ended up running #48 jets, .31 discharge tube-type nozzle and 6.5 powervalve.

I'm running a 30 inch tire at the moment with 2.72 gears through an auto tranny. When I switch to 33's and either 3.91 or 4.11's it'll really wake up, I believe.

When I hit above 2 grand, you better hang on, cause it shoots like a rocket. I walked all over my son in his 4.0 Cherokee on the highway.

[gimmesomerocks]

do you have any idea how a 4 barrel would act with stock compression, and stock valves? I don't really want to go too radical on the internals of the motor, I would even like to keep the stock cam if you think it would work with the 4 barrel.... but I think i'm going to need the cam. My main theme with this is to build a trail friendly presentable CJ with a little pep, and to do it as absolutely cheaply as possible, but not workmanship or build wise cheap...... it will be hard, and take a lot longer, but I want to do it right, but not drain the bank account, especially now.....

[Lawless_Jeep]

I think the Holley 390 will work ok with stock valves and compression. The 390 comes from the factory with #52 jets, .25 standard discharge nozzle, and a 6.5 powervalve. You may need to down jet it some, even below the #48 that I'm running. Mine is borderline too little.

[CJ7Pilot]

My short block is a stock rebuild, bored .20 over, with a mildly ported 4.0 HO head bolted to it. I'm running Mopar MPI on the top end, and a Borla header on the bottom.

Power comes on strong at about 800 rpm, and stays strong through about 2500... it craps out around 3000, though. If I had to do it again, I'd research camshafts a little more. I'd like to have strong power through 4000 rpm at least.

I have to deal with California emissions, so I stayed with the stock cam... but I'm sure there's something out there that would work better.

Have fun!

[wendell]

I'm running the holley 470 TA 4 barrel with offy intake, comp 260H cam, header and HEI distributer, it's a little power house. This summer I'm doing the 4.0 head swap with rollor rockers.

[CJ258]

I am just about done doing a rebuild of sorts on my '74 CJ5. My mains are good with 60 lbs. at start up and 40lbs. down the road and the cam bearing are good. I used the Comp Cam 252H with new lifters and push rods for an '87. The head, intake and exhaust are off an '87 YJ. The head is 9.4 to 1 compression according to the Chiltons, which may or may not be accurate. The OEM head was a 8.4 to 1, again, according to Chiltons. I made an adaptor to run a Rochester 2 Jet, the one with a 3 " throat that was set up for a Chevy I-6 250.
The cam is a little warmer than an RV grind, a little more lift and duration. I'm hoping the later model head is more efficient, the combustion chamber looks better. Jegs has the 2GC for race with either 350 or 500 cfm but I got a rebuild that was milled and bushed for $135 rather than $250. I guess I'm just old enough to remember all the old Chevies that ran that carb with pretty good performance way back when. Just trying something different.

[jeepskate]

I'm no engine guru by any stretch of the imagination, but you have to balance your wants (rough, lopey, idle) with actual usability/drivability. For a 'cheap' mild build, take a look at the Comp Cams Xtreme4x4 cams. I used the 800-5000 RPM one on mine with Summit lifters. My buddy who helped me with the build had a fresh '87 head w/3 angle valve job, so I bought that off of him and slapped it on. New bearings, new timing set (spend the extra for the metal gear...the cheaper ones use a metal/plastic (nylon?) combo that doesn't last as long). Has a stock replacement exhaust manifold on it right now, but I'll be replacing that with a Borla header. I ran a rebuilt stock Carter BBD initially but have a Weber 32/36 on it now. It's 'Teamrushed' (been doing that since the early 90's before TR/JH revamped it) & 'Nuttered' as well.

[curbcrawler]

Originally Posted by jeepskate

I'm no engine guru by any stretch of the imagination, but you have to balance your wants (rough, lopey, idle) with actual usability/drivability. For a 'cheap' mild build, take a look at the Comp Cams Xtreme4x4 cams. I used the 800-5000 RPM one on mine with Summit lifters. My buddy who helped me with the build had a fresh '87 head w/3 angle valve job, so I bought that off of him and slapped it on. New bearings, new timing set (spend the extra for the metal gear...the cheaper ones use a metal/plastic (nylon?) combo that doesn't last as long). Has a stock replacement exhaust manifold on it right now, but I'll be replacing that with a Borla header. I ran a rebuilt stock Carter BBD initially but have a Weber 32/36 on it now. It's 'Teamrushed' (been doing that since the early 90's before TR/JH revamped it) & 'Nuttered' as well.

I just put that cam in. It was an excellent choice.I have other mods too check out my signature. My goal is to make that engine breathe better in and out. You will need internal work done to use a big cam Head milled for one, to bring up compression. A "mild" cam will do you good. The stock cam is so low profile any little bit more of a cam will bring noticable difference. Check out comp cams extreme4x4 cams.

[cyclic17]

I swapped an MC2100 carb, Borla headers, and K&N filter, and was surprised at how much of a difference it all made. Plus, it was all pretty cheap (got the headers on ebay).

Pretty basic upgrades without tearing the motor down.

Oh, and swapped out the crappy plastic valve cover!

[dvbum]

Clifford Performance has bolt on items to improve you engine

http://cliffordperformance.net/index.html

[wendell]

Yeah, you want to be carefull with your cam choice. Unless your gonna drang race, you want a cam that will operate in the low to mid range as not loose your lowend torque. A big loopy cam may sound good, but they tend to operate in the high rmp range where a jeep doesn't see much of on the trails.

[gimmesomerocks]

thats why I was hoping for some sort of cross breed for a cam. something that sounded good @ idle, but still maintained the low end torque I will need. (no racing here)

what are the benefits of doing the swap of the 4.0L head?