As soon as the staff at KT...
As soon as the staff at KT Engines pulled the head on this Windsor Late Model Stock-level race engine, it was clear that there was some major damage that needed to be fixed. The key with a grenaded engine like this is to find all the damaged components and either repair or replace them. If one slips through the cracks, it can quickly destroy your freshly rebuilt engine and leave you right back where you started—but a lot poorer.
In racing, just as in life, eventually bad things are going to happen. It's a lesson most of us learn as kids when that great toy we got for Christmas broke on the 26th.
That's the lesson we learned as kids; the lesson we learn as adults is that sometimes things go wrong and there's nothing you can do about it, but sometimes you can. The fancy word for it is "failure analysis," but it really just comes down to figuring out what went wrong so you can fix it next time. Yes, we like to keep things simple.
With that in mind, we've got a couple of examples of how engine builders attack engine failures to diagnose the problem, or problems, and make sure they don't keep cropping up to bleed your racing budget dry. When repairing or rebuilding a failed race engine, it's also critical to make sure you've identified all the damaged components and either replace or repaire them so that they don't in turn cause a failure of their own.
Here’s a look at the combustion...
Here’s a look at the combustion chamber for that cylinder. From all the damage around the exhaust port it’s obvious that the exhaust valve broke, and steel from the valve was pushed up by the piston and smashed into the cylinder head. The intake valve was still in place, and that partially protected the seat around the intake valve.
While working on other projects with KT Engine Development, two broken race engines came in, one right after the other. The first was a Ford Windsor which the owner had bought used on the cheap and brought in for a rebuild—also on the cheap. "When you are trying to rebuild an engine that you don't know the history on, it's difficult," explains owner Ken Troutman. "You have to do a lot of detective work to try to determine how well the engine builder put it together the first time and how long the parts have been in the engine. It seems like everybody who is selling a used race engine will tell you that it has just been rebuilt, but the reality is that's rarely the case.
"When we rebuilt this Windsor," Troutman continues, "we wanted to replace everything we had a question about, but the customer was on a very limited budget. One of the things we specifically questioned was the valves, but the customer said he didn't have the money. Unfortunately, a valve failed pretty early on and now he's got to spend a lot more money to get the motor back together and running.
"I understand that it can be difficult to spend money to replace parts that look like they should be fine, but the upfront cost of doing things right the first time is almost always a lot cheaper than the cost of repairing your mistakes later."
The second broken engine was a motor that came in from a new customer. This engine had never been touched by KT Engines, and the customer was coming to the shop because of previous engine failures at another shop. This one turned out to be a broken connecting rod, but the real cause is just a bit more involved. Let's take a closer look at both.
Here’s a look at the intake...
Here’s a look at the intake and exhaust valves. The ultra-aggressive camshafts used in modern racing engines are quite hard on valves, especially in classes that require relatively heavy stock-sized stainless steel valves. They aren’t very expensive, at least compared to a lot of the other stuff in the engine, so it’s a good idea to cycle them out relatively regularly.
Any time you have engine trouble,...
Any time you have engine trouble, take a close look at the contents of the oil pan to see what’s made its way to the sump. It’s also a good idea to pull the windage tray to make sure you get it absolutely clean before putting it back on the motor.
Here’s what we pulled out...
Here’s what we pulled out of the oil pan. Luckily, it looks like mostly valve and piston material. There isn’t much that looks like bearing material, so the crankshaft may still be OK.
One of the benefits of running...
One of the benefits of running forged aluminum racing pistons is that they are malleable. Stock cast or hypereutectic pistons can handle large amounts of horsepower under perfect conditions, but they are also quite brittle. In an event like this, a hypereutectic piston would have exploded into a million pieces and there would have been a lot more shrapnel floating through the oil galleries. This looks bad, but it could be worse. Notice the almost perfectly round slug we pulled out of the oil pan that the exposed exhaust valve stem punched through the top of the piston.
Some debris from the piston...
Some debris from the piston got wedged between the cylinder wall and the side of the connecting rod. This rod is ruined, but the rest are salvageable. Most quality rod manufacturers will sell you a single connecting rod, so this isn’t a lost cause.
Along the way, the seized...
Along the way, the seized valves also put enough pressure on the lifters to kill the cam lobes. The faces of the flat tappet lifters are obviously ground away.
Engine builder Ken Troutman...
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...
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...
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...
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...
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...
Finally, we’re ready to start putting things back together again.
If you race a class that doesn’t...
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...
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...
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...
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...
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...
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.