Article 34 Engine Rebuild Part 1
Last month’s article addressed electrical wiring. For the next few articles, I am going to discuss the engine rebuilding process. As some of you may remember, last summer I tore into my engine with the hope of cleaning things up and doing the re-assembly myself using new bearings and rings. That was not to be, as I discovered significant damage to the rings, pistons, and combustion chambers. In my case, repair of the combustion chambers in the cylinder head would require aluminum welding and machining. In order to save my original head, I decided to turn to a specialist for my engine rebuilding work. So after some initial discussions with Dick Maury, the manager of the rebuild shop at Coventry West near Atlanta, the engine was put back together, strapped down to a shipping pallet, and sent by truck to Coventry West.
In preparation for this article, I pondered just what are the reasons for performing an engine rebuild on a Jaguar XK engine. These engines were known in the day to be very robust. Typically, the engine in the car you are restoring will not have extremely high mileage. So why spend time and money on a rebuild? The first reason that came to mind was cosmetics. As part of the engine rebuild, you will have a chance to bring the valve covers, cylinder head, block, oil pan, and front timing cover back to very nice condition, whether it be polishing the stainless steel valve covers to a high luster or painting the iron block the correct sheen of black.
The second reason may be to resolve problems with overheating, low compression, and/or low oil pressure. The rebuilt engine will have all of its coolant passages cleaned out. The compression of the cylinders will be restored via new rings, honing of the cylinder walls, and attention to the valve seating surfaces. Oil pressure will be restored both by cleaning gunk out of oil passages and by resetting the correct clearances at bearings. Also, a few oil leaks may be resolved! So mechanically, there are great benefits to the engine rebuild. Also, although the XK engine is very robust, a few weak links can be addressed, such as getting rid of
cotter pins used by the factory at the piston connecting rod caps. Also, having the engine rebuilt by knowledgeable personnel gives reassurance that the important vital parameters of engine are set correctly. This certainly includes valve timing along with other more subtle issues such as crankshaft end play. And if you wish, enhancements to performance and reliability can be made, such as having the rotating assembly dynamically balanced, using an aluminum flywheel, or adding a modern high torque starter motor. And of course, as in my case, dealing with physical mayhem such as broken or damaged components made a rebuild imperative.
So let’s look at the re-building process. As I said above, I chose Coventry West to rebuild my engine. Coventry rebuilds lots of Jaguar engines so they have seen about everything. My initial concern was the wretched condition of my combustion chambers. They looked like the surface of the moon! I was thinking I might have to source an XJ6 head, which is a possible substitute. But Dick Maury assured that my head could be repaired via aluminum welding and machining. After my initial discussions with Dick, I also came away with the impression that he was very knowledgeable and realistic about replacing the parts that really needed it,
without throwing out the baby with the bath water, so to speak. So we agreed on an overall plan. Certain decisions needed to be made early on. Nothing too earthshaking. I decided to polish up my valve covers myself prior to sending out the engine. I realized later that seeing the state of finish that I applied to the covers allowed Dick to bring the other related bits up to a comparable standard. I decided to go with 9:1 compression ratio on my pistons. The XK pistons can be sourced in 8:1 and 9:1 compression ratios. Dick does salvage some bits out of surplus XJ6 engines, such as the new camshafts with “quieting ramps” and the newer style connecting rods (at
least they were the new style in 1975!). I decided to have Dick’ staff rebuild my water pump. And I decided to have the rotating assembly dynamically balanced (more on that later).
From here, the story shifts to Dick’s shop in Lithonia, GA. By the way, if you choose Coventry for your work, have Dick line up the truck shipment. I found out the hard way that he commands a better shipping rate than I could. For budgeting purposes, I would plan on $250 for shipping by truck from locations in the southeastern US. Dick’s staff receive the engine and perform an initial inspection. Then the engine is dis-assembled and various internal parts are inspected, categorized as re-use, repair, or replace and placed into dedicated storage. When dis-assembly is complete, you are left with the two major components of the XK engine, the head and the block. The head is of course fabricated from aluminum and the block is steel. Both can be cleaned by dipping them in vats of the correct cleaning solutions. Once they are cleaned up, both the head and the block can be inspected for cracks. Dick pressure tests the heads under water at 60 psi to check for cracks and corrosion. In my case, I knew the heads needed work. Here are some before and after pictures which pretty much speak for themselves.
Fortunately, the block itself was not cracked or severely damaged. But there were several cylinder bores with deep gouges, too deep to remove with machining. Fortunately, the cylinder bores in an XK engine are lined with “sleeves”, which are a thin cylinder of very hard, durable metal that if necessary can be removed and replaced. Coventry had their shop replace two of my cylinder sleeves. After machining the top gasket face of the block and applying a new coat of paint, it looked great! Next month we will look at more of the engine rebuilding process.