I have an '82 Scrambler with the 4.2 and Mopar MPFI upgrade. The head on my rebuilt 4.2 (from ProFormance rebuilders out of Springfield, Missouri - now out of business - couldn't happen to a more deserving company) had at least two problems: an external crack that sprayed coolant on the exhaust manifold and valve springs so weak that the valves floated whenever the engine hit about 2700 RPM. I also had an exhaust leak somewhere close to the engine block, either the exhaust manifold was cracked or the exhaust was leaking near the flange. So after some research, I went to Hesco and ordered their "Cylinder Head Conversion Kit #HES4240CHC" along with a Borla header for a 91-92 Wrangler (per recommendation from Benny).
The parts arrived all nicely packed:
- 4.0 head & 4.0 head gasket
- 2 spacers to be used to align the 4.0 head gasket (which has 1/2" bolt holes) with the old 7/16" 4.2 head bolts
- Borla header, gasket, and miscellaneous exhaust pieces
- 4.0 valve cover, bolts, grommets, & gasket
- Rocker spacers for lifter preload (probably remembering this term incorrectly) spacing adjustment if needed
As far as my previous experience, I've changed out long blocks, but never remove the head from an engine before. And I did this by myself. However, there were two pages that I found useful (which I will try not to re-hash too much):
Tim Weaver's article:
Prior to removing the head, I put cylinder #1 at TDC of the compression cycle to measure the lifter preload. The old value was about .032", whereas Benny recommended .050"-.060" on the new 4.0 head.
Removing the old head was pretty much painless, given that I'd been mucking around with the manifolds anyway trying to track down that aforementioned coolant leak. A few of the tappets came loose with the push rods, but they were easy enough to reinstall by hand. I used an engine hoist to lift the old head off of the block and lower the new head on the block.
Placing the new head on the block was kind of annoying, but probably necessarily so:
- The old head bolts are 7/16"
- The new head bolt holes are 1/2"+
- The spacer inside diameter is very close to 7/16"
- The spacer outside diameter is a bit smaller than the head bolt holes and fit precisely in the head gasket bolt holes
The goal is to have the spacer sit on the block, -not- on the gasket, i.e. the spacers should go through the bolt holes in the gasket to the block. The only way I could ensure this is if I put the spacers on the front two head bolts. Otherwise I couldn't see both spacers at the same time. This took a bit of jiggling and lifting up and setting down the head by hand (i.e. without the engine hoist), but things lined up without too much of a sweat. Note that the new head will - not- line up externally with the old block. Don't worry about any overhang as long as you've got the gasket aligned using the spacers.
My lifter pre-load was in the ~.070" range for cylinder #1, and using spacers I brought it down to about .047". Close enough. Benny recommended only checking #1, as they should all be the same.
Installing the rocker arms, push rods, and valve cover were uneventful, other than having to pick up a new fresh air intake elbow for the valve cover. I may have received this in 2002 when I put on the fuel injection kit, but I had been using my original one and had probably thrown it away. Also, on Benny's advice, I placed used some washers to lower the valve cover plate that sits below the metered valve. I used four stainless steel washers, as my 1/4" spacers from my old Clifford valve cover lowered it too much.
One of the above web sites said that the manifold cup washers for the
4.0 were larger than the 4.2 head. This is not true. I ordered new manifold cup washers for a '94 Wrangler from the local Jeep dealer, and the manifold cup washers that arrived were the same size as the old ones.Installing the Borla header and the intake manifold was about as painful as the stock unit. Lots of getting under the Jeep then getting out from under the Jeep. The only thing new is that I had to use a universal in order to get to one of the manifold bolts.
Then it was time for the power steering pump. Crud. The welded nut on the power steering bracket that attaches to the engine block was right up against the header's cylinder #1 exhaust pipe. The Tim Weaver article discusses one possible fix, but after some cutting and grinding, I determined that there was no amount of cutting and grinding that would let the old bracket work - there was a 1/16" space that the bracket could fit into, which meant the bracket had to be paper thin if I wanted a 1/16" space between the power steering pump bracket and the header.
After a day of pondering (i.e. swearing), I came up with a workable solution. First, I cut a small rectangular plate from the old bracket. At one end of the plate was a 3/8" hole for the adjustment bolt. I placed the plate on the back side of the power steering pump over the track used by the adjustment bolt. I then put the adjustment bolt through that plate so that the threads were on the radiator side rather than the engine block side. The head of the bolt rested against the aluminium adjustment bracket, preventing the bolt from turning. I now had a way to tighten and loosen the adjustment bracket to allow me to tilt the power steering pump, but I still needed a brace on the back side.
For the brace, I put one eye bolt in the non-adjustment bolt hole used by the bracket, i.e. the bolt hole on the back side of the power steering pump reservoir. I put a second eye bolt in the threaded hole in the engine block just forward of the engine mount. I then ran a
12" x 3/4" threaded rod between the two eye bolts, with nuts, lock washers, and washers on each side of each eye bolt (i.e. four washers, lock washers, and nuts total). With this, I was able to line up and stabilize the power steering pump. I also retained the functionality of the factory adjustment bracket.The output pipe of the Borla header was about 3" inboard from the existing exhaust. Additionally, the Borla header is a 2 1/8" pipe, while the Scrambler's exhaust pipe is 2". For now, I clamped on an 2
1/8" to 2" adapter and some $5 flexible exhaust pipe. Long term, I plan to use the flange included with the Borla header. Otherwise, things will get messy if and when I'll ever need to remove the header.Now for the moment of truth - the key turn. Then engine sputtered for a couple of seconds, and the garage quickly filled with smokey exhaust fumes. Then things starting running smoothly and the smoking stopped. Next was the test drive, which was a success, with no leaks, no floating valves at higher RPM, and more torque throughout all ranges.
After returning from the test drive, I noticed a ticking noise. Benny suspects that one of the lifter preloads are too low and I may need to adjust it. However, per Benny, this won't cause any engine damage, so I'll probably tackle this in a week or so.
I don't want to give the impression that things went as smoothly as they sound. There were a number of trial and error things, stupid things on my part, many trips to various stores, etc.... However, this is definitely a worthwhile upgrade. The fact that I can take the valve cover off now without mucking with RTV alone almost makes it worth it :)
Michael
P.S. Anyone in the Austin, Texas area interested in an moderately modified (for the Mopar MPFI) Clifford valve cover, a 4.2 head with a
1 1/2" external crack, and a 4.2 exhaust manifold that never quite fit properly? I can get you a real sweet deal :)