Identifying a 258 engine

[jimmydaux]

How can one identify a 4.2 l engine inside a vehicle? I have a family member that swapped a 6 cylinder into his jeep but im not sure what kind it is. Would the easiest way to tell be whether or not its carbeurated?

 

[Rob Mayercik]

Um, look to see if it has a carb. on it?

Leaving aside the obvious answer of looking for a fuel rail and six injectors mounted to the intake, the only hoses coming off the throttlebody of a 4.0 should be vacuum lines to the air box and mainfold.

Of course, in theory one could swap in a 4.2 and then do an FI conversion on it (but why? The 4.2 wasn't rated for more than maybe 105hp with carb).

 

[jimmydaux]

So all 4.0s are fuel injected and 4.2s carbed? Thats what I was thinking. That should make it an easy identification then. THanks

 

[5-90]

Another thing to bear in mind - right up to the last generation of the 258, the #3 and #4 exhaust ports are siamesed - and will have a common manifold entry (I have a 2585 head out in the garage.)

Bear in mind it's also entirely possible to swap the 242ci cylinder head, manifolds, and fuel injection setup onto a 1975-up 258ci engine...

 

[jimmydaux]

Its fuel injected he says, and Im pretty sure the body is a 94 so its most likely the 4.0. Ill probably still steal it from him to use as a donor block and head. Good Idea or not?

 

[j99xj]

AMC cars from the 80s had 258s. So look for fake wood trim and AMC logos and you can be confident its a 258.

 

[Blaine B.]

They used the 4.2 in YJ's too. Or at least up until 1991 I believe.