1969 Pontiac Lemans Cylinder - Sleeve Salvation

The cylinder needs to be taken to approximately 4.055 inch in diameter in order to accept the 0.090-inch sleeve, but it's impractical to remove that much material in a single pass. Willard sets the cutting tip so it removes a minimal amount in the boring bar's first pass and adjusts it so it removes additional material during subsequent passes until the desired total is reached.

He stops the boring bar just before reaching the bottom of the cylinder each time a cut is made. This creates a 0.125-inch step made up of the original wall that's intended to capture the sleeve from the below. Though the cylinder sleeve's outside diameter (OD) measures 4.055 inches, Willard stops 0.0025-inch short of that number while machining the block. The size variance creates an interference fit, which holds the sleeve in place.

Willard left the sleeve in the freezer for several hours before the procedure, to shrink it slightly.

Just before installation, he removes it and sprays a light coating of aluminum-colored paint onto the cylinder wall to act as a lubricant, while the sleeve is driven into the block with a hammer and an anvil. Some also use liquid thread-lock on the sleeve, but Willard feels it has a tendency to ball up from the friction heat that occurs during installation, and once dry, it can actually act as an insulator, compromising the cylinder's ability to transfer heat.

He drives the sleeve into the block until it's firmly seated against the lip at the bottom of the cylinder wall, which leaves excess material at the top.

The portion of the cylinder sleeve that remains above the block's deck surface, Willard removes and trims flush using a die-grinder and cut-off disc.

Next, he machines the cylinder sleeve's inside-diameter (ID) on the vertical boring mill to approximately the original 350-inch bore spec of 3.875 inches. He used the same procedure to install a second cylinder sleeve into this particular 350. Willard plans to overbore the remaining cylinders 0.030 inch to a total of 3.905 inches, and both cylinder sleeves will be machined using the same equipment and at the same time as the others.

If the 350's deck didn't otherwise require milling, a cylinder sleeve can be flush-finished using a flat file. Decking was required as part of this 350's rebuild, however, so final finishing wasn't an issue. Willard cut valve reliefs that match the others by hand using a grinder, however.

This picture proves that after decking, a properly installed cylinder sleeve is virtually invisible.

All eight cylinders of the 350ci block are then bored and honed using conventional equipment and traditional methods.

With two sleeves installed, this block is as good as new. At a cost of approximately $25 for each cylinder sleeve, $100 for each installation, and normal fees to bore and hone all eight cylinders to 3.905-inches, this number-matching 350 will provide its owner with countless miles of worry-free operation while maintaining maximum vehicle value.