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http://www.hotrod.com/techarti...l.html#ixzz1fe5dL4ai75 minute Engine Rebuild - Power Play
There are a lot of things that can be done in 75 minutes or less. Oil changes, car washes, small tune-ups and even the occasional Top Fuel digger motor rebuild. Oh, you caught that last one, did you? That's right, a 75 minute thrash for a total engine rebuild!
From the February, 2009 issue of Hot Rod Magazine
By Jeff Huneycutt
Top Fuel drag racing is famous for vulgar displays of speed: 0-60 in half a second, a quarter-mile in less than 4.7 seconds, and top speeds in excess of 325 mph. It's an arena where brute force is worshiped, and the horsepower is so palpable it literally thumps you in the chest as the cars pass by. For most racing fans there is no better sight than watching two 8,000hp land missiles blast down the track with victory and defeat separated by only a few hundredths of a second.
But the race against the clock doesn't just take place on the track. A Top Fuel engine starts tearing itself apart as soon as the driver releases the clutch. Pistons, rods, bearings, the crank, you name it; when you are talking about the equivalent power of one-fourth of the starting field in a NASCAR Nextel Cup race in a single engine, every component's life span is severely compromised. Many parts are capable of surviving more than a single run, but no team is willing to press its luck by making even a second run without checking everything first. After every pass, a Top Fuel engine is completely torn down and rebuilt in an amount of time that most engine builders find is barely enough to gap rings. In an IHRA-sanctioned event, teams are allowed 90 minutes between rounds, but NHRA teams are given just 75 minutes to completely rebuild the engine, make whatever chassis adjustments they deem necessary, and get back on the line.
During a rebuild, all major components are removed and either inspected or automatically replaced to be rebuilt later. The only major pieces that remain in the block are the crank--although the main caps come off so they and the bearings can be inspected--and the camshaft. Everything else, from the blower to the oil pan and even the clutch, is removed by a crew that works largely with only a few air- or battery-powered tools at its disposal. The crew spends as much time inspecting parts as they come off or go on the car and looking for potential problems as they do actually turning wrenches. After all, any mistake during reassembly can lead to an engine failure, and an 8,000hp race motor never fails in a small way.
Besides simply getting the engine back together in time, there is the added pressure that comes from the fact that any mistake during reassembly can lead to dire results on the racetrack. A crewmember never focuses on the idea that a mistake on his part could be punching a ticket for his driver on the maim train, but protecting the driver is always a concern. "I have complete trust in my crew," says five-time IHRA Top Fuel champion Clay Millican. "But you have to have confidence in your crew because there is literally an 8,000hp bomb sitting behind your head, and as drivers, a lot of times we are lighting the fuse."
To the uninitiated, an engine rebuild in a Top Fuel pit appears to be pure mayhem, but there really is a science behind everything. Typically, a crew consists of seven to nine members, and each has a specific responsibility. For example, the Werner Enterprises/Kenny Koretsky Motorsports team that Millican drives for has a clutch specialist, two men working on the bottom end of the motor, two men on the cylinder heads and valvetrain, one whose responsibility is the blower, team manager/co-crewchief Lance Larson who helps with the blower and wherever else is necessary, and a helper or two to clean parts and do the leg work. Still, that's a lot of people crowded around (and under) an engine, and real estate can get noticeably scarce."You have to have patience while at the same time working at a quick pace," says cylinder-head specialist Justin Crosslin. "You can't worry about getting bumped into or hit with hot oil because it's going to happen. You just have to let it go and get back to work."
When the car arrives in the pits after a run, the crew simultaneously attacks the engine from the top, the bottom, and in the case of the clutch man, the back. The goal is to eventually meet in the middle. Ideally, by the time the gigantic cylinder heads are stripped off the block, the bottom-end guy has the rod caps off and is ready to push the piston and rod assemblies out the top of the block.
To save time, some major components are replaced as a chunk. The cylinder head, complete with headers, springs, valves and everything except the rocker-arm assembly, comes out in one piece and is replaced by an assembly that's been built ahead of time. This head will be rebuilt during the downtime between rounds and put back into service.
Reassembly takes about twice as long as teardown. Although many of the components can be reused, they won't be until after the crew has a chance to thoroughly inspect each piece. Each new round's assemblies, including complete cylinder heads, pistons and rods, and clutch packs, are already prepared and ready to go well in advance. The Werner/Koretsky team normally keeps eight sets of cylinder heads in rotation and has the ability to perform basic rebuild operations at the track.
At the track the team looks for specific signs that can indicate further damage. For example, the cam never leaves the block under normal conditions. When pulling the lifters, a good cylinder head man will quickly spin the roller for the exhaust lifter over his palm to make sure it rolls smoothly. Exhaust lifters will almost always go bad before the intakes because the exhaust valve has to open against so much pressure, and Miller says that if the lifter is bad, that almost certainly guarantees it has wiped that cam lobe on the last run. The main bearings also display predictable wear patterns. The engine's incredible power tries to push the crankshaft out the bottom of the block, so wear on the top half of the bearings is surprisingly little. Unless the bearing has spun or Miller notices the bottom bearing shell is blackened, he knows he has several passes before he must go to the trouble of getting the crank out of the way so he can check the upper bearing shells.
Normally the Werner/Koretsky team is tightening the final bolts on the engine at the one-hour mark. That leaves at least 15 minutes to fire up the motor and check for any signs of trouble before heading back to the track. Over the course of an NHRA weekend, that can mean eight passes in the familiar winner-keeps-racing format. That also means seven complete rebuilds over three days in conditions that are usually less than ideal. When your shop is an awning attached to the side of your race hauler, your parts washer is a can of brake cleaner and a roll of disposable shop towels, and your workspace is the patch of greasy asphalt underneath the engine, it can make eight successful passes down the track look like quite an achievement.
00:00 - Car brought into pits; crew begins pulling carbon-fiber side panels
00:30 - Tool organizer in place on top of driver's 'cage; plug wires and fuel lines begin coming off
01:00 - Ballistic covers off engine; clutch man has puke tank removed
03:05 - Valve covers off
05:00 - First wheel is off; oil pan is drained and removed
06:00 - Blower off
07:10 - First main cap comes off
08:00 - Shaft-mounted rocker-arm system off heads
08:15 - Cylinder heads off
08:45 - First rod cap is off
09:30 - First piston and rod assembly removed; cylinder-head men begin checking cylinder bores as pistons come out
10:00 - Bellhousing off
11:15 - Final piston/rod assembly comes out; Miller begins replacing lower bearing shells in the main caps
13:00 - Final clutch pieces come out
14:15 - Lifters out
17:00 - New clutch pack goes in
17:20 - First of new piston/rod assemblies go back in
19:05 - Last piston/rod installed; final main cap and bearing shell checked
26:20 - Last main cap bolt torque'd
29:00 - Bottom end buttoned up including pan
31:20 - Head gaskets in place
32:15 - First cylinder head in place
35:00 - Pushrods installed
35:30 - Rocker-arm assembly bolted down
42:00 - Engine oil poured through lifter valley
45:00 - Belt and pulley system installed
50:30 - Intake manifold in place and checked for flatness
54:30 - Blower placed on intake manifold
55:00 - Blower belt in place, begin lashing valves
60:00 - Valve covers on
62:00 - Spark plugs in and wires on
65:00 - Double-check motor before warm-up