Top Fuel Breakdown
Clay Millican gives us a tour of the inner workings that make today’s ultimate three-second hot rod
Words And Photos: Todd Silvey
Over time, there have been lots of news articles geared toward the general motorsports fan concerning the “costs per pass” of a Top Fueler or Nitro Funny Car. These articles estimate the range from $8,000 to $15,000 per pass, depending on how you factor in things like team, transport rig(s), and travel expenses.
Drag Racing Scene wanted to get a Top Fuel tour and dig a little deeper into today’s top nitro warriors and take an in-depth look at the components that make up the dragster. Our first-hand tour guide is Clay Millican, driver and all-around great guy with the Great Clips/Parts Plus/UNOH dragster.
As we began, Clay would basically touch a component on the car and give us his input on the details of each piece of hardware. He began by grabbing and explaining two of the most outward components to their fueler: the massive front and rear wings. The front wing in recent times has graduated from two canards on each side of the dragster’s front nose to a full-size wing that rivals the downforce of the rear wing at their 300 mph speeds.
“The rear wing is an insanely critical part of everything,” Clay says. “We run an Aerodine Composites Group carbon fiber rear wing, which is actually the main wing and two elements above it. The rear wing makes about 10,000 pounds of downforce at 300 mph. So, if the rear wing leaves the car, the car becomes an arrow, literally without any feathers, and it will no longer go straight.”
“The front wing is also an Aerodine Composites component and makes about 3,000 pounds of downforce at 300 mph,” Clay continues. “The wings have to be SFI re-certified, so they’re sent back to the manufacturer every year to be checked for any type of damage that may have occurred during the season. We really try to take a lot of loving care of the wings, as they are such an important part of the car going down the track.”
“As far as wing adjustment, we don’t move the main element that much, but we do adjust the two upper elements a good amount. You’ll see teams moving them in the staging lanes. When the air is really dense and good, we will lay them down because the air on its own is heavier, so it makes more downforce automatically. When it is really hot and nasty, we will raise them up to create more downforce.”
The spill plates (the side sills on each side of the wings) also involve a lot of science, but the teams aren’t able to make any changes to those on their own. “We do not alter them — the manufacturer has to alter those,” Clay says. “Any changes have to be made by the company, because all of that has to go through the SFI Foundation.”
There are multiple Top Fuel dragster chassis builders depending on the driver and what the crew chief decides will work best. “Brad Hadman is our chassis builder, and I believe he has more Top Fuel championships than any other builder out there,” Clay says. “They’re a pretty flexible car, and Brad is unbelievably easy to work with. Physically, teams will front-half their cars after about 75 runs. They come in and cut the front half of the car off right in front of where the driver sits and replace all of that tubing. The cars are so flexible, that you wear that tubing out.” There is also a current trend where many teams are designing and building their chassis “in-house” at their own racing headquarters.
“Every team has its own engine-driver location, how far is the driver from the rear end of the car, how high up or down is the front of the motor, and that is determined by the crew chief,” Clay says. “The chassis builder will make the cars accordingly. The chassis is set up solid for the most part, but for us, we have two diagonal bars that are adjustable. We don’t move them a whole lot; they are mainly for when you hit the throttle, that it actually lifts the front end of the car square.”
Brakes are a very important component on a Top Fuel dragster and need to be amazingly good. “They are four-piston calipers,” Clay says. “There are a couple of different brake manufacturers, but we use Lamb brakes. They are carbon fiber rotors, carbon fiber pads, and you’re looking at about $5,000. We replace the pads four times a year and the rotors twice a year.”
“The ideal situation, especially in a dragster, is you release the chute, cross the finish line, and step off the throttle,” Clay describes. “When you feel the chutes hit, it kind of settles the car down, then you grab a handful of brake. It’s not a panic stop, but you are definitely pulling on the brake pretty good, and then you’re off and on the brakes needed to make the turnoff at the end of the racetrack and keep the chassis settled. If you get the car bouncing, you have to let go of the brakes and let the car settle back down. It will definitely happen, but the brakes on these cars are pretty incredible. I’ve stopped the car many times without the parachute for different reasons, and I have also put the car in the sand trap from lack of brakes at times.”
The rear end, besides the chassis, is one of the most dependable parts of the racecar. “We run a Chrisman rear end,” Clay says. “They have a 12-inch ring and pinion in them. They’re all the same gear ratio, being mandated at 3:20, though we would run a higher gear ratio if they would allow us. We will make 60-70 runs with essentially no maintenance, other than inspecting it after every weekend and replacing the oil in the rear end every weekend. The ring and pinion gears have to be replaced after 60-70 runs, and there’s not much else on the car that lasts that long, other than the chassis. So, if you put a fresh rear end in, about the time you need a ring and pinion, it’s front-half time. It’s pretty much direct drive with a reverser, and that’s it. It’s a solid spool with a nice big old tube going through there that’s splined on each end for an axle.”
There are a lot of different manufacturers for the clutch. “In the case of our car, we run a CNC Performance Engineering clutch,” Clay explains. “They build clutches for a lot of the guys. All of the components, including the pressure plate (what we call the donut) the stands that actually separate the pressure plate from the flywheel, and the flywheel itself, are critical to everything we do. There are 18 different levers in the clutch, and there are numerous different ways to run the clutch. Every crew chief has his own method and runs his own levers in the clutch. That is a very crew chief specific area that is such a huge part of the car.
“For us, that is our crew chief, David Grubnic’s baby,” Clay says. “I want to point out that when we smoke the tires, people watching will say the clutch was wrong. That’s not necessarily true. The clutch can only do what the motor tells it to do. The motor needs to do the same thing every time we step on the throttle. If we can make that motor achieve the same engine rpm every time we step on the throttle, then the clutch will do what it is told to do.”
The team needs to predict what the engine is going to do with the clutch tune-up. “It’s easier to maintain a certain level of engine rpm at the step of the throttle than to make clutch adjustments. You have to do something the same every time, so it’s easier to make the power level the same no matter the weather conditions. We can always add or remove blower overdrive, nitro percentage, ignition timing, so whatever their number is — and most teams are between 8,200 and 8,800 rpm at the step of the throttle, they can then adjust the clutch for what it is supposed to do. That doesn’t mean it will always do it every time.”
The typical lifespan of clutch components is short-lived in a Top Fuel dragster. “The clutch disc will make one run and then it has to be resurfaced as a result of the incredible heat it generates during each pass,” Clay explains. “It will typically make two runs and it’s life is over. The pressure plate lives for hundreds of runs, but it has to be maintained. The levers have to be changed, and the donut has replaceable facings that get changed every 20 runs or so. Those facings are actually put on a flywheel grinder every single run.”
Each clutch disc has its own characteristics, so there is very detailed record keeping that takes place. “Clutch discs are typically made in batches of 400 to 600 at a time,” Clay says. “The next batch they make could be just a touch different in material than the other batch. We keep track of what disc are in the car, what batch they are, we keep several batches in a clutch pack. We want a selection of different batches, so when we run out of one, we’ll introduce only one new batch to the mix at a time.”
The injector hat is another Aerodine Composites Group component on the car. “There is a lot of development work that goes on with these,” Clay says. “The way they look on the outside isn’t necessarily how they look on the inside, but a hat is a critical part of the car because it’s what directs the air into the top of the supercharger. It is a relatively trouble-free part, and we don’t have to do any maintenance work on it, other than making sure the blades are centered correctly in the openings. We also have to make sure the place where the barrel valve bolts on maintains its integrity so you know it’s not going to fall off the car.”
One of the biggest things being developed in nitro racing right now is the supercharger. “It is definitely the hot item on the car,” Clay says. “We run a Darren Myer Performance Engineering (DMPE) 18-71 Top Fuel supercharger, and it’s about $20,000 for each one. There is a lot of development going on just for the fact that if you can get it to produce more air in a slower over-drive, we’ll have a more efficient component.
NHRA limits what can be done to the supercharger rotors. “What is happening now is a lot of development in the cases, the openings, the inlets and outlets, and the type of strip we use to seal each rotor lobe to the blower case. Each rotor has two strips on them, and those strips get changed about every four runs. No matter how hard you try, you will find you have a supercharger where one is better than the other, no matter how identical they are. Every team has their favorite.”
Cylinder heads require a lot of work as well. “We run Alan Johnson Performance Engineering Stage 7 heads,” Clay notes. “These heads arrive CNC ported, so we don’t touch the ports on the heads. After every single run, we do a valve job and check the valve springs. We sometimes have to put valve guides into the heads. We closely check and replace the valves, because they’re typically not straight anymore after a single pass. Sometimes, we can use special tooling to straighten the valves, and sometimes, they are beyond repair. We typically get four or five runs out of a valves or valve spring. It’s just non-stop checking to be sure what still falls in our tolerances.”
The team is prepared with multiple sets of heads at the beginning of each event. “Our team will typically leave the shop with eight sets of heads ready to bolt on, one for every run we can make during a weekend,” Clay says. “Also after every time you run a head, you need to check the chamber volume (CC’s) in each head because when you do work on the valve seat, now you’ve sunk the valve down or replaced the valve. It’s crucial because you could drop a cylinder — nitro motors are very dependent on even compression between cylinders under a load. So, we CC-measure them every time, and that determines what thickness of head gaskets we put on. Head gaskets are changed every single run, and that is determined by weather. That goes back to trying to make that motor do the same thing every run. We want to maintain that same engine rpm back to the clutch, and that all goes to compression which is determined by head gasket thickness and chamber volume.”
Clay moves us to the engine block, a more durable part of the engine, but there is still maintenance to be done. “The short block is a TFX billet block and it does take a beating, but unless you damage the block by throwing the rods or other breakage, they’re pretty durable,” Clay says. “After about 20-30 runs, the centerlines need re-align bored in them. Blocks do take a beating, but the sleeves are replaceable, so unless you hurt it, you don’t have to do a lot to it.”
Crankshafts are another very expensive consumable of Top Fuel racing. “Crankshafts are about $4,300 and right now, an average crankshaft is living a six- to eight-run life,” Clay says. “These things make so much cylinder pressure that stress cracks form on even the toughest material. We keep up with the cracks as best we can during a weekend, and after a weekend, we pull the cranks out and magnaflux them. We keep a logbook with each short block and will know which crankshaft went into each short block. We try to maintain consistency because there are only a few things in the motor that remain consistent, including the crankshaft and the camshaft.”
Cam timing is also one of the most important aspects of the current nitro engine. “Because we change rods and pistons every lap, we change cylinder heads every lap. It goes back to consistency and making sure that every single engine cam timing is the same, no matter which short block we have in the car, is critical. We run a COMP Cam, and that’s all I’ve ever run in my entire career. We typically put 20-30 runs on a cam since they also are taking a huge beating. There is so much cylinder pressure, the lifters are trying to break these things in half. Some of the gigantic explosions that have been seen in recent years have been from camshaft failure, so we replace them. If they have made 25-30 runs in a Top Fuel dragster, they’ve done their duty.”
Lifters and pushrods are taken out after every single pass. “We put them in a sonic cleaner, then we closely check the rollers,” Clay says. “We check them for feel, size, and about every 20-30 runs, they get sent back to COMP for a rebuild. They are a very vital part of the whole thing; valvetrain problems in a nitro car are huge and ugly.”
We don’t keep a run count on pushrods, but they will tell you when it’s time to change them,” Clay explains. “They’ll let you know when they’ve gotten hot. We also check them for straightness every single run too. No questions about that one.”
Connecting rods will typically make about eight to 10 runs and are changed accordingly. Pistons are changed as needed. “We don’t keep a round count on pistons as they will tell you when it’s time for them to be changed. We check them after each run in many different ways. We look at the ring lands first, then look at how much dish is in the top of the piston. We know what it was before we made a run, so how much did it droop in the center after the run, and we have a small tolerance on that. If you can feel any scuff with your hand, that piston is done. Every rod and piston in the trailer have a journal kept on it.”
Every fuel pump is different, and a Top Fuel dragster uses a gigantic pump with two sets of gears in it. “The fuel pump is a huge part of the tune-up,” Clay stresses. “A typical fuel pump now is from 110 to 120 gallons per minute (GPM). We monitor them, so that when we freshen a pump up, we will put them on a flow bench and recheck them. But, the race car is the ultimate flow bench. It will tell you through all of the sensors we have in the Racepak data recorder that will tell us the flow rate when we first step on the throttle, how quickly does that fuel get in the engine, and how much the pumps are flowing during a pass. A fuel pump typically costs in the neighborhood of $8,000 each. Our team typically keeps a couple of them in the trailer at all times. A fun little tidbit: When we compete at Denver, we put a smaller pump on it since there is less air to mix with the fuel.”
“When I turn on the top bulb, I have my foot on the clutch and the car is sitting there in neutral,” Clay continues. “We have a predetermined fuel flow on the burnout, backing up, and staging where a gate valve that is cracked open and bypassing a large amount of fuel back to the tank. Once it is time to stage, you will hear a nitro engine change in tone — that is when I reach over and turn the fuel pump all the way open towards the injectors, by necking the return valve. Now, the engine is receiving all of the fuel from the pump into the engine, except for a small bit. A lot of extra fuel comes out of the headers, and the engine rpm drops. The car is wanting to go, but we’ve taken our foot off the clutch, so the motor is tugging a little bit. The pre-stage is on, and we proceed to bump forward using the hand brake to stage the car. The tree flashes, and then the fun begins.”
The ignition is two, 44-amp MSD magnetos that fire at one time and is one of the more long-lasting parts on the car. “We can adjust the timing going down the racetrack through an MSD box, which is NHRA approved and checked often due to a mandated built-in rev limiter, in an attempt to keep the cars from going too fast,” Clay comments. “Crew chiefs adjust the timing on every run, trying to give the most power without losing traction. The MSD mags are sent in once a year to be checked. Unlike early magneto designs, the capacitors utilized by the mags live a long time. We do change plug wires every other race, just because of the pure amperage put through them. The coils, the boxes, all that stuff, we change once or twice a year… just because.”
The controllers are probably the most held-to-the-chest item used on a Top Fuel Dragster. “We have basically the same as everybody, a timer box from Electromotion,” Clay says. “It’s not horribly expensive, but it can control items based off of time. For example, it can control the fuel system. The fuel regulator is hooked to this box, and we build a fuel curve on the computer screen, and it will then function the fuel system according to what this map looks like. The clutch is also controlled by these electronic timers.”
Wheels and Tires
Goodyear is the only manufacturer of the tires for the nitro classes, and typically they put six to eight runs on a set of tires. “That doesn’t necessarily mean six consecutive runs,” Clay points out. “We have tires stacked everywhere and those tires will all have a different circumference and roll-out. We change tires according to the conditions and are changing our gear ratio with that rollout.”
Wheels are one of the more durable items on the dragster. “We are only one of a couple of teams that are running the Delta One wheel by Weld Racing,” Clay says. “It is a single billet aluminum wheel with beadlocks, and there are not any other wheels out there like that. It is by far the strongest wheel on the market and that’s a safety advantage, as well as a performance advantage, because it’s lighter.”
Oil and Fuel
The oil used in the car is an SAE 70 nitro oil from Valvoline. “It is a nitro blend that Valvoline has worked on for years and years,” Clay says. “It’s absolutely trouble free. The biggest battle is fuel contamination. When we do a warm-up, we will change the oil afterward, just because of the fuel contamination. So much fuel is being pushed in those motors, the rings simply can’t keep it all out of the crankcase.”
Mixing the blend of nitromethane and methanol is usually the responsibility of the driver. With Clay, that is his responsibility as well. “It’s a time-consuming process, and it’s not hard, so I think the crew has us do it just to keep us busy,” Clay jokes. “It used to be harder than it is now. We have an electronic fuel checker to tell us what the percentage ratios are.
The maximum allowable nitromethane percentage according to NHRA rules is 90 percent nitro. The crew chief will make a decision before every run and tell me what percentage of nitro he wants. A drum of fuel comes to us at 100 percent nitro, and we have to cut it with the methanol.”
Transporters and Hospitality
Clay’s team has three rigs on the road for each race. One trailer hauls the race car, and inside of that same trailer is the maintenance tooling, spare parts, short blocks, and equipment for maintaining the superchargers, cylinder heads, and more,” Clay says. “The second trailer is more of a machine shop and kart hauling trailer where they maintain the rods, pistons, as well as the clutch parts.
The third trailer is the hospitality trailer. “That one is hugely important to our team. We entertain close to 5,000 customers a year, with our various sponsors. We feed them, we do everything we can to entertain them. That’s what pays for all of this operation to compete. NHRA’s access is what separates us from all other forms of motorsports. So, our team tries to make sure we do a really good job to entertain the people who are coming to see us. That’s very important to us.”