Wanted to recommend this swap to anyone running a 4.2L, what a difference.
The power from the engine is so much smoother its like a night and day difference. I wouldnt say there is more low end power but just more across the rpm range. Before I did the swap I read it is a 40hp increase, my but dyno says thats about right, with the greatest increase above 1500rpms.
What I used was a head and exhaust manifold from a 97 grand cherokee 2wd. The head has the 7120 casting number, which still has the temp sensor in rear of the head.
Some notes for reference:
make sure to get the pushrods and rockers from donor engine, the pushrods are shorter on the 4.0 head than the 4.2.
the late 4.2 valve cover is a direct fit on the 4.2 head, so if you have one keep it, so you don't have to change the breather/pcv routings.
when using the 97 2wd grand cherokee exhaust manifold, also get the downpipe, the o2 sensor bung is in there and its much easier to mate the downpipe to the existing exhaust rather than making a whole new one.
modifications-
Cylinder head. blocking coolant ports, use packing peanuts(corn starch based, dissolve in water), and epoxy/cold weld of choice. block the coolant ports on the intake side of head.
Some 4.2L blocks have a larger head mating surface, to where the coolant passages do not need to be blocked, i wasn't that lucky. It is a good idea to check before you block them off.
the powersteering bracket required clearancing at top of bracket where it bolts to intake manifold.
the intake manifold, the bosses for the dowel pin-remove 1/8" or so metal from bottom of boss, do not have to grind all the way through to hole.
also on the intake manifold, had to remove lower rear and lower front corner piece, about an 1/8" triangle of material to clear exhaust flange.
auto tranny shift linkage bracket. had to cut a large v out of the bracket to clear exhaust flange. after removing the material, put a brace on the topside of bracket to make up for material loss.
on the exhaust, removed old downpipe and cut converter square flange off with 2" pipe remaining, to mate to downpipe from 97 chero.
It is a long swap, took roughly 15hrs or so this weekend to complete, started early saturday and finished by noon on sunday.
Tuning, depending on fuel delivery system your running you made need to retune the carb or adjust settings on computer. I run a gm based tbi system, and no tuning was necessary, once the engine warmed up and entered closed loop, the o2 sensor kicked in and all was good.
The power from the engine is so much smoother its like a night and day difference. I wouldnt say there is more low end power but just more across the rpm range. Before I did the swap I read it is a 40hp increase, my but dyno says thats about right, with the greatest increase above 1500rpms.
What I used was a head and exhaust manifold from a 97 grand cherokee 2wd. The head has the 7120 casting number, which still has the temp sensor in rear of the head.
Some notes for reference:
make sure to get the pushrods and rockers from donor engine, the pushrods are shorter on the 4.0 head than the 4.2.
the late 4.2 valve cover is a direct fit on the 4.2 head, so if you have one keep it, so you don't have to change the breather/pcv routings.
when using the 97 2wd grand cherokee exhaust manifold, also get the downpipe, the o2 sensor bung is in there and its much easier to mate the downpipe to the existing exhaust rather than making a whole new one.
modifications-
Cylinder head. blocking coolant ports, use packing peanuts(corn starch based, dissolve in water), and epoxy/cold weld of choice. block the coolant ports on the intake side of head.
Some 4.2L blocks have a larger head mating surface, to where the coolant passages do not need to be blocked, i wasn't that lucky. It is a good idea to check before you block them off.
the powersteering bracket required clearancing at top of bracket where it bolts to intake manifold.
the intake manifold, the bosses for the dowel pin-remove 1/8" or so metal from bottom of boss, do not have to grind all the way through to hole.
also on the intake manifold, had to remove lower rear and lower front corner piece, about an 1/8" triangle of material to clear exhaust flange.
auto tranny shift linkage bracket. had to cut a large v out of the bracket to clear exhaust flange. after removing the material, put a brace on the topside of bracket to make up for material loss.
on the exhaust, removed old downpipe and cut converter square flange off with 2" pipe remaining, to mate to downpipe from 97 chero.
It is a long swap, took roughly 15hrs or so this weekend to complete, started early saturday and finished by noon on sunday.
Tuning, depending on fuel delivery system your running you made need to retune the carb or adjust settings on computer. I run a gm based tbi system, and no tuning was necessary, once the engine warmed up and entered closed loop, the o2 sensor kicked in and all was good.
Comment