| INTRODUCTION: In this article I am going to explain the basic
fundamentals of a not-so-hard shadetree mechanic head conversion on a
4.2L 258ci engine block. As I'm sure any Jeeper knows, these are the
engines that mainly came in the CJs and early YJs. After several months
of research, I came upon some discoveries about putting a 4.0L head on a
4.2L block. Apparently the block on a 4.2L and 4.0L are very similar
except the 4.2L has a longer stroke and a few design differences. After
I sent several e-mails trying to find out more information about this
conversion, I was informed that this conversion is possible and can
provide a 40HP gain. That's right, 40HP! I was a little surprised
myself. Not only does this conversion add more HP, but I have read that
people have experienced a substantial increase in gas mileage; approx.
17-18%. I began searching for a 4.0L head and found just
what I was looking for at Koller
Dodge (check their website for more
details). They provided a remanufactured head, completely rebuilt and
basically new. From here there are a couple of retro-fit modifications
needed to make this work right. Don't worry, they don't require any
difficult procedures or special tools. Below is a picture of my new 4.0L
head upon arrival via UPS. PARTS LIST:
- 4.0L Head Provided by Koller
Dodge
- 4.0L Head Gasket
- 4.0L Exhaust Manifold or Header
- Exhaust Manifold Gasket
- 4.0L Valve Cover
- 4.0L Valve Cover Gasket
- Tubes of QuikSteel Epoxy Putty
- Sand Paper (fine) REMOVAL OF OLD 4.2L HEAD:
This part was a dream come true. I have wanted to
remove the old head and intake system for as long as I've owned the
Jeep. I started by removing the air cleaner, valve cover, power steering
pump, radiator hoses, etc. NOTE: I didn't remove the Carter carb and
intake yet because I had other plans involved with the intake system.
(Check next months issue for more details) Anyway, after removing the
rocker-retaining bolts and removing all of the rocker arms and rods, I
then removed the head bolts. Now the old 4.2L head is ready for removal.
The pictures below show the head removal process. (Click on images for large view) INSPECTION AND CLEANING:After the 4.2L head, intake, and carb was removed,
I was really surprised to see how clean the cylinder walls and pistons
were. This engine currently has 98,000 miles on it and appears to be in
really good condition. I was afraid that I would discover some problems
upon removing the head like excessive carbon build-up or scratched
cylinder walls. I guess it makes sense since the engine never burned
oil. Well anyway, I cleaned whatever I could while the head was off. I
scraped off the entire surface before installing the new head. INSTALLATION: PART
1: The first step is to prepare the head for
installation. After you've obtained all the parts from the parts list,
you will need to perform the following task. In order for the 4.0L head
to work on the 4.2L block, I had to fill in a couple of water jackets in
the 4.0L head. They are the small triangular water jackets on the same
side as the intake. These must be filled because on the 4.2L block these
water jackets don't exist. I made a couple of calls and came to the
conclusion that the best way to fill these holes is to use a high
temp epoxy putty. I bought two tubes of QuikSteel. This is a 500 degree
max temp super strength epoxy putty found at most auto parts stores. Since the holes in the head expand inside it makes
it much easier if you use foam-packing peanuts to fill in the holes. I
used one packing peanut for each hole. This makes applying the epoxy
much easier. Don't worry, the foam peanut will dissolve. After filling
in the holes, make sure there aren't any burs or pieces of epoxy
sticking up above the head's surface. I used some fine sandpaper to
ensure the head would match perfectly to the head gasket. It's very
important that the head is completely smooth to ensure no head leaks,
compression loss, or blown head gaskets, etc. Below are some pictures of
the holes filled in. (Click on images for large view) BEFORE PLUGGING WATER JACKETS:
AFTER PLUGGING WATER JACKETS:
DIAGRAM 1.3 This diagram shows exactly which holes need to be
filled on the new 4.0L head in order for the conversion to work. NOTE:
It's very important that you plug only the holes that are shown in the
diagram. If you accidentally plug additional holes in the head it could
cause your engine to overheat or cause other problems. See diagram below
for details. INSTALLATION: PART
2:After the preparation of the head is complete,
you're ready for the installation of the new 4.0L head. I suggest having
a friend help place the new head on top of the 4.2L block. The head
alone weighs 77lbs and when you're trying to line up the head on the
block while also trying to align the head gasket all at the same time,
it would be very difficult as a one man job. I started by placing the
new head gasket on the 4.2L block, then with the help of my friend Nate,
we lowered the head down onto the block. It was surprising how well the
head lines up. It appeared to fit as perfect as the 4.2L head. (Click on images for large view) INSTALLATION: PART
3:After placing the head onto the 4.2L block, it's
time to mount it down. It's recommended that you use new head bolts
because of accuracy, but the old head bolts will still work. For my
application, I used the old head bolts. A new set of cylinder head bolts
are $17.00 from Mopar Performance (Part #: 4529204). I was unable to
find new head bolts in time for the installation. It's very important
that you torque the head bolts down in order and to the right torque
specifications. I created a little diagram below to view. A
similar diagram can be obtained in a Haynes or Chilton's repair manual.
The first round, you want to torque the head bolts down to 22lbs
of pressure. (I recommend using a quality torque wrench for better
accuracy). On the second round of tightening the head bolts, torque them
to 45 lbs of pressure. On the last round, tighten all the head bolts to
110 lbs of pressure except head bolt #11, you must torque this bolt to
100 lbs of pressure. NOTE: Before installing the Number 11 head bolt,
put some Loctite 592 sealant on the bolt. All these torque ratios aren't
custom or created for this installation; these are basic head bolt
tightening specs, and can be obtained in your Jeep repair manual as
well. Click on Diagram 1.1 for printable size. (Click on images for large view) Diagram 1.1 Torque Sequence INSTALLATION: PART
4:The next thing to do is install all the rods and
rockers. When doing so, you will want to set the engine at TDC (Top Dead
Center). This means the number one piston must be at the top of the
cylinder. To obtain this, you must move the harmonic damper until the
mark is directly pointed at the 0 position on the timing settings. After
the motor is verified to be at TDC, place the rods into position as you
took them out. After placing all the rods back into position, mount the
rockers back on as you took them off. When bolting the rockers down, it
is very important that you don't under or over tighten them. The
dealership recommended torque specs say to torque them to 19 lbs. Now that the head is in position and mounted, you
can place the valve cover on. Be sure to use a new cork valve cover
gasket. I'm not sure of the torque specs for the valve cover, but it's
specified in your Haynes repair manual. Check your Haynes or Chilton
repair manual for exact specs. Below are some pictures of my Jeep with
its new 4.0L head and valve cover mounted in position. (Click on images for large view) INSTALLATION: PART
5:Now that the 4.0L head is mounted and ready,
you're going to need a 4.0L header or exhaust manifold. For my
application, I had a friend that had a spare 4.0L header from an 88'
Jeep Cherokee lying around. Since my project is on a budget, I put
this header on for now. I highly recommend using a Borla header. Be
aware that the intake manifold and exhaust use a lot of the same
mounting bolts. There is no need to customize anything, except you'll
need to mount the intake manifold and exhaust at the same time. There is
also a specific torque sequence and lb. amount for these bolts as well.
I created another chart to specify these torque sequences. Torque the
intake/exhaust manifold to 23 ft/lbs. (Click on Diagram 1.2 for
printable size) Diagram 1.2 Torque Sequence INSTALLATION: PART
6:After completing the installation of the new head,
it's recommended that you use different spark plugs. For my Jeep, I
bought Bosch Platinum platinum +4 plugs. They're a little more expensive
than most and I'm not sure if they will even make a difference, but I
figured I would give them a try. Torque the spark plugs to 27 ft/lbs. INSTALLATION: PART
7:From here, put your carb back onto the intake
manifold including all the vacuum lines, fuel lines, etc as you took
them off. Hopefully you marked all the hoses and lines so that they can
easily be put back in their proper locations. If not, the vacuum
diagrams can be obtained in the Chilton or Haynes repair manual.
Everything should bolt right back into position except the rear power
steering pump mounting bracket. This needed a little modification, which
is pretty self-explanatory upon installation. 4.0L HEAD CONVERSION FINAL EVALUATION: The overall conclusion of my 4.0L head conversion
was definitely two thumbs up. The cost was fairly inexpensive compared
to the amount of power gained. Although I've done minor engine repairs
and modifications before, I have never done anything even remotely close
to this and, to my surprise, it was pretty easy. The overall
preparation, old head removal, and new head installation took about 5 -
6 hours. This may vary depending on the tools used. I can't say exactly
my overall results of the power since I'm currently adding additional
engine modifications. (See next months issue for more details). I can
say that from speaking with fellow Jeepers on the Internet that have
performed the same conversion the overall performance increase is
substantial and well worth the time. TO GET STARTED ON YOUR
4.0L HEAD CONVERSION, CONTACT KOLLER DODGE AND THEY CAN HOOK YOU UP WITH
A REMANUFACTURED HEAD AND NECESSARY PARTS TO CONVERT YOUR JEEP. SEE
INFORMATION BELOW FOR DETAILS. | 
Posted Nov 30 2007 10:29PM
