258 differences

Can anyone tell me if there are any major differences between 258's of different years???
There's a rebuilt head on Ebay for a 83 to 89, any way that would work on a 75????
Thanks in advance,

High5 :stout:

 

One is the size of the head bolts. I know my '83 258 had a different size head bolt then my 72.

check out http://www.andersonengines.com/IMAGES/AMC.pdf
for some information. These are the guys who rebuilt my 258.

 

Valve cover design too. That range should have the plastic cover.

Re the head bolts, they're either 1/2" or 7/16". I had thought that most years are 1/2", but that AMC had changed to 7/16" around 1980 for 1 or 2 years. You can make either head fit - if you have a block with 7/16" bolts, HESCO sells sleeves that fit in a 1/2" head. If the head is 7/16" and the block is 1/2", it can be machined to the larger size.

Sorry - this is not what you asked, but are you sure you want to buy a head on ebay? Shipping will be a big expense, it's not the right part, and 258 heads are cheap and plentiful. Buying from a local shop makes much more sense. What the problem with the head you have now?

 

Ahhh,
Nothing is "wrong" with the head, as far as I can tell. I was just curious why they would advertise for certain year range when I thought they were all the same.
Thanks for the clarification,


High5 :stout:

 

One more thing,
Does anyone have a 258 that actually runs "good"??? I have changed carb, intake, and ignition and it still doesn't start "easy" and takes a couple of minutes to warm up before it runs good. It is just the manor of the beast??? I have timed it and timed it again with no real improvement. Don't get me wrong, it runs a hell of a lot better than it did, but not perfect. I have heard that FI really wakes up the engine, but I don't have that kind of coin to throw at it right now.
I'm a little concerned about this up coming winter and cold starting. For the last many years it was asleep in my dad's heated garage and never was run in the winter months.
Thanks for the help

High5 :stout:

 

Yes, but there are caviats....

I am running fuel injection and a DUI HEI ignition. All the unnecassary emmisions plumbing are gone. (Nice thing about FI) I basically have the evap canister and PCV hooked up. No other emmisions, although I am considering putting a cat back on it to help out because I do care about the environment. (the other nice thing is a 72 does not have to do the emmisions tests in Texas). Also running a newer 3 wire GM alternator.

With these 3 upgrades I was able to rip all of the existing wiring and vacuum lines out of the engine bay and greatly simplify everything. The engine bay is clean and neat. Of course you have to be willing to completely rewire the whole jeep to do this.

 

I had a '75 CJ-6 with a 258. Ran very well. Boy, I could shift at 10 & 20mph and never have to shift again unless I had to stop for a traffic signal - very smooth at low rpm. Was a little gutless on long uphills (2nd was too low, 3rd too high - the T18 ratios are better), but otherwise, no complaints.

My J10 runs fine, although I think I jetted it a little too lean. Has a bit of a stumble going to WOT at low speed.

 

My engine has a ton of power, with the HEI, new Motorcraft carb, and the split header into dual exhaust through glass packs, but it sure doesn't run "smooth". There is a pretty good lope to it and vibrations. I'm pretty sure it has been rebuilt, so I guess it could have a lopey cam in it, but I'm not sure. I can't complain about power, because I have an ample supply of it. I remeber before we put the header on it was a bit gutless. I think at that time it also had the single barrel carb.

I don't have any sort of emmisions on it, nor do I have a return line from the carb back to the tank. Is this extremely necesarry?? I just have the line to the carb and that is it. I have been having a problem keeping the vacume line from the carb to the HEI on. It seems to come off on it's own. I think it's too short, I guess I should have replaced it while I was doing the carb/HEI upgrade recently. I better get that done.

I do drive this to work and back about 3 miles or so everyday so it is my daily driver. I would like it to start better and run a bit smoother without upgrading to FI. Too many other things I want to do first.

High5

 

I had a '79 CJ with the 258 and it always had a rough idle even after new carb and ignition parts. I decided to yank it off and have a valve job done and had the shop mill the head down after they said it was warped. That thing ran so smooth I couldn't tell it was running unless you hit the gas. I'm not sure what fixed the problem, the valve job or the milling, but it sure ran sweet after that.

 

Valve job eh???
Never thought of that. I think the head has been ported, but I doubt it has had anything else done. Come to think of it, the Jeep ran much better before we put this head on it. Maybe I'll get that old head off my Dad, I mean from my Dad R) and have some work done to that. This new head does have some valve noise anyway.

Thanks for the help

High5

 

Inline 6s, as a group, are reeaallly smooth. I remember one of the fathers in my scout troop had a Rambler wagon with an idle that was undetectable if you weren't holding on to the steering wheel.

A compression check will detect a bad valve - a compression checker casts $25 at Pep Boys. instructions included.

Valve noise usually comes from worn or gunked-up lifters, not the head.