Re: 4.0 Head on a 258

[farna@xxxxxxx]

You should be able to use either 258 or 4.0L parts. There is no difference in the timing chains. In fact, all parts that fit on the block are the same for the 258 and 4.0L. I have a late 70s 258 timing cover on my 4.0L now (pulled engine from a wreck and discivered a crack in the cover, local pick-n-pull had platny 258s, no 4.0L). The 4.0L block has all the bosses for accessory mounting as the 258, even the Eagle front axle bosses. The only difference is the block is about 1/4" wider at the top (bottom end at engine mounts is the same width) and there is no boss/hole for a mechanical fuel pump. You will need to run the 4.0L pushrods. I believe they are a bit longer than the 258 pushrods because the raised ports mean a little taller head. I haven't physically checked this, just sounds reasonable and everyone I know who has done the conversion uses the 4.0L pushrods.

Yes, a failed upgrade wiped EVERYTHINg from the board. Probably operator error, and he should have made a backup first, but these things happen! AMCyclopedia had an unexpected HD crash and lost everything as well. Haven't had time to put much back on myself!  If you were registered on the new forum at www.amcforums.com you will have to re-register, as registration info was lost too. 

On May 7, 2005 Todd Tomason wrote:

> Fran,
> 
> Did you mean www.amcforums.com?  I went over there and signed up to see what
> you said, and apparently Branden accidentally wiped all the messages about an
> hour ago when an upgrade failed.  Would you mind reposting it here?
> 
> I recently purchased a 4.0 cylinder head from Clearwater Cylinder Heads that's
> supposed to have had the appropriate holes already welded up.  This a
> rebuilt head with the appropriate valve work, etc. already done on it.
> 
> I guess my biggest question is where do I still use 258 parts, and where do I
> use 4.0 parts?  For example, I assume I can use stock 4.0 rockers.  My 258 is
> an 83 that is in a Spirit.
> 
> I'm also thinking that this is a good time to replace the timing chain.  I
> heard somewhere that you can use a 4.0 timing cover on the 258.  True?  It's
> supposed to have a cam button.
> 
> Keep in mind that this is all pretty new to me.  I only did my first intake a
> couple of months ago.  I've never head a head off of an engine before.
> 
> Todd


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