hey guys just looking for some input on unforseen problems OK I am taking A 91 xj motor HO with automatic trans (trans not going in other xj ) and installing it in an 90 xj with the manual trans any input is appreciated thanx

 

Just use the block. There are different set ups and alot of the parts wont work on it. In 91 they switch to the chrysler system. so you will see like the thottle body is different. so basicaly just the block and head is the same.

 

The head is not the same. 87-90 4.0 engine have the Renix system and the 91 and up models are the Chrysler H.O. system. The ports on the head are different and will not flow well when mismatched. You can get a H.O. block and head to run with the Renix intake and throttle body, but the performance and fuel mileage will suffer.

 

well yes they changed to the 7120 head in 91. but as far as getting the motor to work it is fine. I have a 88 block and head in my 91. Sure it maby not flow the best but it works and at least its on the road.

 

If your Jeep is 91 and the head is a 91 then yes everything will work fine. I'm talking about using the Renix head with a H.O. intake or vice versa. The intake manifold and the head will not flow well when mismatched. The engine block is the same and will work with either head

 

i have a 91 in my 89 and all I used from the 91 was the longblock,all my components including intake.exhaust,dist,flexplate are from my 89,it does bolt up easy enough but it does not have the power it did before,This is due I think to the intake/exhaust do not flow as well as the 91,for me this engine runs very well and the loss in power is not an issue for me,I am building a stroker and will put it in at some point,but this motor runs to good to not use it.

 

I have the 88 block and head with all the 91 parts. intake exhaust dist. It works just fine for me. Like Abovetimberline and I have to agree the power loss is not a problem for me either. My cherokee is on the road and runs great.

 

wow thanx for the info so what if I am going to use the entire engine including head throttle body and intake still will it be that difficult I was originally thinking about using the entire HO system hoping to just pull it and drop it in my 90 because my 91 I originally rolled it and took everything off lift etc.. but scored on this donor 90 xj but it had A blown motor......

 

If you wanted to do that you will need to transfer the pcm,wiring harness,and exhaust,the 91 does not exhaust vertical like the 90 does.
When doing this remember that the two are different and only the longblock is the same,even the head is a bit different.

 

wow more trouble than its worth I wanted remove replace and get back to the mountains looks like I need to sell the HO block and get A 90 block in there dont need extreme power just need to do some crawling...

 

there are a few things different your flywheel is gonna probably be different but your throttleblody from the newer motor can be made to work but its pretty difficult i just did this same thing also your fuel lines are gonna be a little different you will run into a few problems which with out the right tools stuff can become pretty unreasonable