Questions about the 258 from 1980 vs. 1986?

[PoliceMonkey161]

Ok......So maybe someone can clear this up for me. I just got a 258 of a 1980 to use as a rebuild project for my 86 CJ. I'm not a stranger to rebuilding engines, but a professional either.


So, my question is: What is the difference between the two years? I have not torn the 80 apart yet, but when I went to start ordering some of the basic parts there seems to be difference between kits for the 80-81 and the 82-86 but I can't find any solid info on what is different? :scratch:

 

[69jeepcj]

I found this: There are two generations of 258 engines. The first generation was introduced in 1971. This earlier engine has cast iron intake and exhaust manifolds with the two manifolds bolted together by 4 bolts and a gasket between. In 1981, AMC revised the 258 for lighter weight. A new block casting and fewer crankshaft counterweights were used. A new smoother exhaust manifold and aluminum intake manifold were introduced. V-belts were replaced with a serpentine belt, and a new lightweight plastic valve cover was fitted. Although these two generations have the same bellhousing and motormount attachments, and are mostly the same internally, the differences must be kept in mind when choosing used replacement parts.

 

[PoliceMonkey161]

Thanks......

 

[frhrwa]

I have a copy of the JEEP CJ 81-86 FSM that covers everything there is to ask about those years.. if you want a copy on DVD, pm me a name and address where to send it.. it beats the crap out of Haynes and Chiltons.. wayne

 

[carnuck]

If you have a tin valvecover, then it's the eariler stuff (71 258 is a year by itself for crankshaft and bellhousing. Starter is driver's side) '72 up got the same bell as AMC V8 with self centering flange and starter pass side. They lightened the crank the first time late '78 and again in late '81 when they went to plastic valve cover. They changed the thrust bearings (which is part of the kit differences) and pistons went from flat top to dished for emissions.
The cylinder head combustion chamber got bigger 3 times from '71 to '90 for emissions clean up. The last few years with aluminum valve cover stock are the same head as Renix 4.0L without the notches for the injectors.

 

[PoliceMonkey161]

If you have a tin valvecover, then it's the eariler stuff (71 258 is a year by itself for crankshaft and bellhousing. Starter is driver's side) '72 up got the same bell as AMC V8 with self centering flange and starter pass side. They lightened the crank the first time late '78 and again in late '81 when they went to plastic valve cover. They changed the thrust bearings (which is part of the kit differences) and pistons went from flat top to dished for emissions.
The cylinder head combustion chamber got bigger 3 times from '71 to '90 for emissions clean up. The last few years with aluminum valve cover stock are the same head as Renix 4.0L without the notches for the injectors.

Awesome info....... Thank you!