[803]

First off, I really did try to use the search, but all of the info I found was for 1986 and older. I am under the assumption that the engine I have is a 1990.....how do I tell, are there any sites that have the build date codes?

I have a 258 block with a casting # EF3235444
the stamped code near cyl # 2 is 803CX29
and there was another number 02388

question # 2

Are all 258's the same..can parts be swapped from a 77 to a 90? if not what parts can I interchange?

thanks

 

[JimmyZ]

Head bolt sizes changed. I think my '79 had 1/2" while the '85 had 7/16".

 

[1652]

For engine codes try this

HTH

 

[lah2420]

I have an early '87 that came with an '86 block. The casting number on it is EF3235444 also, if that helps any. The head bolts changed back to 1/2 inch in '86, although the tops of the ones on the manifold side measure 7/16". The threads in the head are 1/2" though. I think they basically stayed with the same block through '90. The only date codes I could find were through '86. After that, they went to a code on your VIN for ID purposes.

 

[803]

Now that I think I have an 89 258 can I use the flywheel from an 81?

 

[lah2420]

I have a '75 motor in the shop now to replace my worn out '87. I am using the '87 flywheel and head on the older motor. The only real difference I can find is that my crankshaft and block are much heavier on the '75 than the '87. Otherwise, all my '87 parts fit each motor. If you have an automatic, it may be different. I don't know about that one.

 

[lindy80cj7]

Aren't they externally ballanced? If so, wouldn't you have a problem putting a newer flywheel on the old crank?

 

[Guest]

Nope the 6's are naturally balanced, and you can swap flywheels without a problem. Just use the correct clutch for throw bearing clearence. Also if fuel injection is in your future you might consider using a 4.0l flywheel. It has the tone notches for the CPS. Much cheaper and easer to do now while you've got the chance.

 

[lah2420]

Here's the info I went off of to determine the flywheel needs. This is part of an answer I received from my question to jeepdoc.com. They haven't led me astray yet.

"The difference: later flywheels are lighter than the early ones were but they have the same balance, same bolt pattern, use the same ring gear and are interchangable so it is ok to use your 1987 flywheel on the 1975 engine."

If anyone has different info, please add your opinion and the source. I just want to do this right the first time as I'm sure 1977CJ7 does.

Thanks lindy and swift. Your comments are greatly appreciated.

 

[803]

Thanks guys

 

[MarineOpLaw]

PHYSICS LESSON PLEASE!

Wouldn't the earlier (heavier, thus more inertial energy) flywheel be preferable to the later/lighter one if you were looking for more torque? In that same vein, wouldn't using a lighter flywheel w/ the older/heavier crank be giving up (actual loss of) torque?

My knowledge of physics is almost nil, therefore why I am asking the most basic of questions.

 

[uglyjeepoffroad]

Heavy, early crank + heavy early flywheel = idling over stuff

Heavy, early crank + heavy early flywheel + 4.0 head= idling over stuff and still pulling that hill on the way home in top gear!!!!!!!

 

[WILL]

The heavier the flywheel, the more it resists rpm changes. Good for constant rpm, bad for quick acceleration.