Engine Failure Analysis - So It Broke, Now What?

Engine builder Ken Troutman had originally hoped to be able to resleeve the damaged block and save it. But after it was torn down he discovered that all eight cylinders had already been sleeved. Since he doesn’t know the history of this block, or even what brand or thickness of sleeves had already been used, the decision was made to simply replace the block.

Never assume that any component in a broken engine has escaped damage. For example, at KT Engines the teardown of this Windsor included the oil pump where they found damage to the gerotor pump. This pump will probably still function, but the scratches on the lobes will degrade efficiency so it will be replaced.

The crank journals didn’t have any damage, so after a quick polish it was ready to go. Even though the rods and pistons were replaced with components that were practically the same, it’s still imperative to rebalance the rotating assembly.

Troutman had a replacement flat tappet camshaft ground to the same specs, but again, you can never be too careful so take the time to degree in the camshaft again.

A new block and bearings means you will need to check the bearing clearances as well as the crankshaft endplay again.

Finally, we’re ready to start putting things back together again.

If you race a class that doesn’t allow any work to the cylinder heads, then the damaged heads would be junk. But KT Engines was able to touch up the combustion chambers to get rid of the sharp edges that would otherwise lead to detonation. You can still see some signs of the previous damage—in order to keep the head legal, KT Engines limited the amount of repair work to the minimum.

Back on the dyno, the Windsor had good oil pressure and duplicated the horsepower production from the previous rebuild. It’s ready to race.

Here’s a Chevrolet Limited Late Model that also came through the shop. The broken connecting rod is obvious, and we suspect the cause is a broken rod bolt. A spun bearing can also sometimes be a cause but we doubt that here because there is still some bearing to be found. Usually, a spun bearing burns the bearing away to nothing and then heats the rod until it breaks.

When the rod broke, the piston contacted the head pretty severely. Notice the imprint of the edge of the combustion chamber on the bottom portion of the face of the piston. Not only is this piston junk, but we’ll need to inspect the cylinder head closely for stress cracks.

Unfortunately, although only one cylinder is damaged this block is a lost cause and can’t be sleeved. The broken rod has chewed up too much of the bottom of the cylinder bore and the cam tunnel. If you tried to sleeve the block there is little chance the new sleeve would be able to seal against water pressure at the bottom of the cylinder.

The broken rod also managed to chew up the windage tray in the oil pan. The pan itself doesn’t show any signs of damage, so hopefully a new windage tray will be all that’s needed here.