How to tell if I have a 258?

Fluffy73 wrote: Close.  If we're discussing the 70's era, when 232 and 258 were produced side by each, the only difference between the two engines are connecting rods and blocks. The 258 has the longer stroke and taller deck.

This just reminded me of something that doesn't make any sense. Has anyone here ever seen a 232 with steel stamped rockers? I always find solid beam rolling pivots. Maybe that's the easier way, just open the oil fill cap and peek at the valvetrain.

Hello all, Here is some of what I have learned...

The deck height of the 232 block design was changed to a taller deck height when the 258 was introduced about 1971 in order to accommodate the longer stroke, the 258 and 232 share the same block at that point on.

The cranks are different of course because the difference in CU is done by stroke. The bores are the same and of course the Rods are going to different. 258 has shorter rods due to longer stroke than the 232. And the 232 early had that shaft rocker system at only 1.5:1 rocker ratio, upon the change to the pedestal type they went to 1.6:1.
 EDIT-Addition: I think that is right farna... They used the shaft type till 1974. They may have started with the new style on the 258 and used up some remaining old style on the 232 longer? Not sure on that...  Daemon Force.

Another few differences to note... early on the Borg-Warner auto trans was used and the sixes had a different bolt pattern on the block. Around 1972 the blocks were changed to match the bolt pattern of the V-8. The early crank had a different business end. You can make an old 232 crank work on newer stuff if you machine out the hole in the end of the crank. There is a pilot hole, it is smaller early on.

My six I have been building up is a 1972 258 block bored .040 over, the crank from my 70 232 with the end machined etc., and 199 rods with a modified 1995 4.0 7120 casting head. That is at least 25 years span of parts just in the engine! AMC engineers really had their head on well. They kept building upon what they learned and what was known instead of throwing it to the wind every few years or so like other makers and ending up with new problems most every time.

There were quite a few head improvements over the years, even into the 4.0 era, 3 major changes I know of then. For the 4.0 they raised the height of the intake runners which took out kind of a knee angle that was impeding, resulting in a more efficient flow.  Intake valve size is larger on the 4.0 heads than the 232/258 ones.

I went with the 232 stroke it just seemed to have more top headroom, does not have that Six cyl feel.  In making the 4.0 they pulled the stroke back closer to the 232 I noticed also. They increased the bore.

Hope this helps a bit. I been in n out of the sixes a little over the years and this is probably my last one. I got some worn out parts myself LOL.

Take care!
Blitz



Edited by Blitzman - Jul/16/2016 at 10:58pm

So, Mr. Neville, what engine do you have? gz

you can actually see the boss its stamped on in the picture a couple of posts back.

She's a 258!