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swapping out an 87 4.0 for a 91 HO


NAXJA Forum User
New Hampshire
Hey everyone!
just got web access back, planning on swapping a motor next week.
My 87 knocks, has lost alot of power and needs injector work.She just broke the 300,000 mark. I have a 91 in the driveway at 150k that was my last short lived trail rig. Driveline is tight but she's rotted right out and a little tweaked from airtime.
I have both rigs complete, both have AW4.
Going to do cam and bottom end bearings, rear main and mounts.
Anyone know where to find a good write up or thread?
My big questions are fuel/electronics and which cooling system to keep.
(HO system is better by far, but everything on the non-HO was replaced last year) Anyone done this recently?

Check out the search on this it's been gone over many times.

I used the HO controled by the Renix computer. Requires swapping all of the sensors across including the distributor (I would replace that since yours has 300K). You will have to adapt the old TPS to the new throtle body. Someone showed some pics of a pretty slick way to adapt a few weeks ago.

The only issue I had was the fuel lines. Some of the older ones had a quick connect at the base of the firewall and others did not. My donor motor had the pressure and return lines at the front and my old motor had the pressure at the back and the return in front. Since you have the whole rig it shouldn't be a problem to swap the lines from one to the other.

Be patient, it's a holiday weekend and everyone is out having fun but us. :D
Thanks! That's a good start.
Tried a quick search but couldn't find much.
Don't think I was asking the right questions.
Finding much more now.

The cows forgot to tell me it was a holiday weekend!!