MECHANICAL
(Engine)

The Big Bang theory
Here's what happens when a piston separates at freeway speed. From underneath, you can see the bent piston rod hooked on the oil feed pipe. The old-style, long-skirt pistons contain oil-drain "slots". It is my theory this led to stress cracks, which eventually caused complete separation. Piston chunks & wrist pin are visible in the oil screen. The crank was a writeoff, and the rod punched through both sides of the pressed-steel oil pan.

The rebuild
The engine is a true 3.4L 9:1 compression engine with C-Type head, of which only about 200 were produced. Because of rarity, I felt it was worth rebuilding correctly. OEM "wedge" pistons were unobtainable, so I had CP Pistons build an updated version of the originals. I'm also fitting an aluminum flywheel, later model vibration damper, sturdier connecting rods, and a gear-reduction starter.

A big shout out to Kurt at Engine Parts Service for his exemplary machine shop work and sage advice. Also, big thanks to Mike at CP Pistons for fabricating something "better than new", and for treating me with the same respect as if I were John Force (unlike some nearby JErk piston mfr).

Thanksgiving, 2007:
More engine progress - setting the correct ring gap:

December 22, 2007:
I test-fitted everything, measured with plastigage and there's nothing left but to build the short-block. Following Kurt's advice, I brought out the hose and detergent, scrubbed the bejeezus out of the block, then blew it dry. Armed with Johnson Pre-Lube and Valvoline 50W racing oil, I installed the crankshaft. After setting the correct end-float, it was onto the pistons. I aligned the ring gaps per CP Pistons instructions, and dropped into place. I was surprised how "proud" the pistons stood up at TDC, but that's the idea. With a 9:1 compression ratio, and hemispherical combustion chamber, it's like a Mopar 6-cyl "hemi". After I mount the head, I'll "CC" the chambers, so I can choose the appropriate head gasket thickness to avoid pre-ignition (details below).

View hand-cranking video

December 30, 2007:
Time to strip cams, power-wash the head, grind the valves, and set valve clearances in preparation for reuniting head with block. See valve spring compressor on Page 4 for more detail.

January 12, 2008:
I finally received my 100ml burette. This allowed me to precisely measure the displacement of one cylinder, and calculate compression ratio. This is important because in California, we only have 91-octane "premium" fuel. Anything over 9.5:1 compression ratio will cause pre-ignition. I can "tune" my compression ratio to around 9:1 by ordering a head gasket of a calculated thickness. Thanks to my friends on Jag-Lovers for providing the Excel spreadsheet and instructions.

January 17, 2008:
My calc's looked funny, mainly because I took one measurement wrong. I pulled out the burette and remeasured, and plugged in the new number:

This spreadsheet shows compression ratio is 9.84:1 with a standard .015" head gasket. This is too high.

This spreadsheet shows the results when I bump the head gasket thickness up to .050". It bumps the compression ratio down to a nice 9.23:1, which is exactly where I want it.

February 17, 2008:
I found 3 bent intake valves. I expected the #5 cylinder to be history because that's the piston that split in half. Puzzling why the other 2 were bent. Regardless, I brought the head into my favorite machine shop (Yo Kurt!) to have the valves and valve seats cut to the correct angle.

I'm retrofitting later 4.2L valve seals to the head. The intake valve guides are already renewed. Now I'm scouring the internet to find "cheap" 4.2L valve spring seats, retainers, and split collets. All have to be changed out to fit the valve seals.

I spent the morning at Jay's cleaning parts. I'm prepping for bolting the head on the block, so everything has to be surgically clean. So, into the parts washer, blow it dry, spray it with WD-40 (water-based washer solution), and pack it away in plastic bags to keep dust and dirt at bay.

Easter, 2008:

Got my head back from the machine shop. Cut the valves & seats, skimmed the head. Might need to weld & mill the water ports - it's open for discussion. Note the nice 3-angle cut Kurt put on the exhaust valve seats. I placed my new composite head gasket (still wrapped) on the head for your edification.

Here are a bunch of oil feed tubes. Since I have replaced the oil pump with a later 4.2L model, the intake port is 1/8" larger. However, I can't simply use the larger 4.2L tube since the 3.4L oil pan is different.

Here's the simple solution, suggested by some folks on the Jag-Lovers site: Use a resize bushing. For $5, you can solder a bigger bush on the end of the old, small pipe, and you're done. However, it bugs me not to take advantage of the increased volume potential.

So, off I go on another adventure. To mimic the 3.4L tube pickup point (albeit in a larger diameter), I need to chop about 6" off the 4.2L tube, and perform a bit of fabrication magic....

March 28, 2008:

OK, I tried, but wasn't up to the task. I found a "big bore" oil pipe from Guy Broad Jaguar. It arrived this week, and it's awesome. It's all stainless. I had to cut the flange a bit, and build some custom support brackets, but it's now in place, sturdy, and the pickup tube height is spot-on (8 3/4").

Compare the old 3/4" pipe with the new 7/8" pipe. This should deliver a 16% increase in the volume of oil to the pump.

With that done, I should be able to lock down the bottom end (finally). After fitting the timing chains, I can bolt on the oil pan, and turn the block right side up to begin work on the top end.

June 1, 2008:

Armed with my new valve springs, valve seals, and a variety of adjusting pads, it's time to build the head. Valves in, valve seals (intake), springs and collets next, "baseline" adjusting pads, tappets, cam bearings, and cams. I've measured the gaps, and am ready to remove the cam and swap out the pads with those of the correct thickness. See my "Tools" section on Page 5 for a finger-saving tool. Specs call for a tappet clearance of .006" intake and .009" exhaust. I may add .001" to both measurements figuring I'll lose that much when everything beds in.