Drag racing remains a popular form of motorsport in many countries. In addition to races at the top tiers of the sport, where competitors have in excess of 10,000 bhp (7500 kW) available, there are historic or retro classes that continue to run cars which ape those used a few decades ago. These classes encompass everything from hot rods to Top Fuel dragsters and Funny Cars.
The main differences between modern and retro classes is the power output and the look of the cars. There is a significant difference in performance between the same type of cars from four or five decades ago and their modern descendants.
In RET 90, November 2015 (1), we reported on how we had teamed up with AVL to use its torque sensor to reveal for the first time the actual power output of a contemporary Top Fuel V8. The result was a figure of 10,156 bhp for the Don Schumacher Racing ‘Army’ car as measured running on the Maple Grove Raceway in Pennsylvania in a test the day after the 2015 NHRA Keystone Nationals at that track.
Running on 85% nitromethane, this Nostalgia Nitro Funny Car engine is restricted in terms of performance by supercharger size and fuel flow rate – however, it still produces 2500-3000 bhp (Courtesy of Geoff Monise/Quarter Pound Nitro Funny Car)
Controlling power
It would, of course be possible to transplant a 10,000 bhp engine into a car resembling a 1970s Top Fuel or Funny Car, but that rather misses the point. The Nostalgia classes of drag racing aim to replicate the appearance and performance of the cars of years gone by, without specifying that original machinery must be used. When engines and their components have such a short lifespan at these extreme levels of output, mandating original components would very quickly lead to the death of this class of racing.
The limiting factors in terms of power output are fuel flow rates and airflow rates. The former is managed by mandating a maximum flow rate of the fuel pump, the latter is managed by placing restrictions on the size of the supercharger used.
Where the best modern Top Fuel cars can exceed 330 mph (530 kph) over the 1000 ft (304.8 m) course, the retro racers are more sedate and still run the longer quarter-mile (1320 ft) course. The times for nitro retro cars to 1000 ft are about a second slower than the best modern Top Fuel times.
We spoke to competitors in the UK (Andy Hadfield) and US (Geoff Monise) about their experience of running in retro classes, their engines and the demands and challenges of their race weekends. Although both compete with similar V8 engines, there is a difference in the scale of their budgets, staff and race weekend activity.
In the UK, retro drag racing is still very much at the enthusiast/hobby end of the scale, with competitors building their car and engine in their garage and financing it from their personal income. In the US, drag racing has been big business for decades. Don Garlits and his fellow racers were making six-figure sums from drag racing 50 years ago, and although retro drag racing doesn’t attract that same level of money, the US teams are generally better funded. Hadfield and Monise therefore have very different perspectives on competing over the quarter-mile.
Hadfield describes competing in drag racing very much in amateur terms, calling it a hobby. “Alcohol is a cheap fuel by most standards, so actually getting the car up the track isn’t horrendously expensive, but parts can cost a staggering amount. A good crankshaft can cost more than £4000 and a set of pistons is over £1000.”
Andy Hadfield’s alcohol-fuelled Altered-class car runs on methanol to produce 2000-2500 bhp. Despite appearances, Nostalgia drag classes have engines made from all-new components (Courtesy of Callum Pudge)
These costs may not seem high in comparison to some of those that some of us are used to, but we should consider that drag racing in the UK is largely a self-funded activity. The cost of putting a powertrain together to compete in the Altered class for example is pretty high, according to Hadfield. “A complete engine build will cost around £30,000-40,000, while a gearbox capable of holding the horsepower would cost £6000-10,000,” he says.
The costs involved mean that building new engines regularly is not an option for Hadfield, “My particular engine is around 11 years old but most of the parts that complete it are newer,” he says. “Because of the high compression ratio and boost levels from the high-helix supercharger, wear is a factor so regular inspection, checking and replacement is vital. All in all, it’s not a cheap hobby and there are no rewards other than beating your own personal best times and perhaps beating
Modern engines
Hadfield’s car runs in the Altered class and is what many people would tend to call a hot rod in terms of its looks. The engine is “based on the design of a big block Chevrolet” but Hadfield notes of his 600 cu in (9832 cc) alcohol-burning V8 that “there is not one part in the engine that is stock – everything is either aftermarket or custom”. He estimates that his engine produces around 2000 bhp and 2000 lb-ft (2712 Nm) of torque from his methanol-fuelled engine.
Monise competes in NHRA-sanctioned retro competition in his nitro Funny Car. He says, “The engine is based off a 426 street Hemi produced by Chrysler.” Expressing the same point as Hadfield on the lack of commonality with the original engine design, Monise notes that “everything is custom made and the only part that is usable from a street Hemi is the distributor hold-down”.
Monise estimates that his engine produces around 2500-3000 bhp and 2500-3,000 lb-ft of torque on a mixture of nitromethane and alcohol. Estimating engine output is common in drag racing. Dynamometers to measure the huge outputs are uncommon, but the main reason is that the lifespan of an engine on full throttle is often in single figures of seconds. In any case, the competitors find little merit in accurately knowing the output of their engine in the same way as competitors in circuit racing.
This image shows the top part of the supercharger drive. The supercharger is ‘jacketed’ for safety reasons (Courtesy of Geoff Monise/Quarter Pound Nitro Funny Car)
It’s clear that these racing classes are ‘nostalgic’, ‘heritage’ or ‘retro’ in name and appearance only as far as the engine is concerned. There is no requirement to run any period components or original engines, and indeed very little to prevent unrestricted development within a minimal set of regulations that restrict performance to levels similar to those possible in the chosen era of competition. The NHRA rule book governing every aspect of Nostalgia Nitro Funny Car competition – from the driver's clothing, chassis, engine, bodywork, safety, material and so on – is contained in only 14 pages.
A common thread that runs through much historic racing is the use of engine components of modern design and materials produced using modern manufacturing methods. In the types of racing where there is nothing to restrict performance, we effectively have modern engines operating inside original castings and producing levels of performance far in excess of those typical of the period.
Monise says, “The ‘spirit of the 1970s’ limits us to the look of the car [that is, body style and year], but the engine components are all brand new and have the latest designs and materials.” However, there are regulations that restrict potential power output by limiting the amount of chemical energy going into the engine.
The modern competitor in nostalgia drag racing is able to benefit from the same modern techniques used in modern motorsport, for example being able to use billet blocks and cylinder heads that are much less likely to have manufacturing faults such as internal material defects than castings. The better material properties of modern, clean wrought materials also improves component reliability.
The greater used of accurately machined complex surfaces such as ports and chambers provides more consistency in terms of performance cylinder to cylinder and between engines: the favoured port and chamber shape can be quickly reproduced in every head. Although it removes some of the artisan skills from the past, it does help keep component costs low and improves the availability of parts (and the profitability of the suppliers).
Parts supply
Neither Hadfield nor Monise suffers any particular problems with getting parts for their engines. The number of large-capacity V8 competition engines operating in the US means there is a very healthy market for components for many of the popular engines used in drag competition, and this satisfies demand from other countries too.
Even in the UK, Hadfield rarely has to wait more than 2 weeks for parts, while Monise generally has excellent availability of all parts, noting that, for his Chrysler-based engine “everything is available from the manufacturers here in the US. It has come a long way in the past 10 years so not much is made ourselves.”
What has affected parts supply though, and has created supply problems in the wider automotive world, has been the coronavirus pandemic. Monise says, “Because these cars are nostalgic in appearance only, they are all brand new parts under the body. In normal circumstances, finding parts is relatively easy. However, owing to supply issues this year due to Covid and other issues, parts are taking much longer to be built or repaired. For example, we ordered new rods after our last race and we were told it would take at least 10-12 weeks, which led to us not being able to compete when we wanted to.”
Supercharger restrictions
Given that the engines comprise all new parts, I ask Monise what the rules are concerning the engines so that they remain true to period in terms of engine design and performance. “The main rule is that the head stud location must remain stock, as must bore spacing,” he replies. “The maximum displacement is 500 cu in, the cars must have a 6-71 style supercharger. The fuel pump can be a maximum of 21 gallons a minute [1.6 litres/second] and we are limited to one spark plug per cylinder.”
On top of that, there is a further restriction on maximum intake area as measured at the butterflies.
The capacity, stud location and bore spacing ensure that the retro aspect of design is complied with, while the supercharger and fuel pump restrictions effectively control performance by restricting air and fuel flow respectively. Modern Top Fuel engine regulations are much tighter, dictating bore size and a slightly smaller bore spacing than the Nostalgia rules. There is little doubt though that these engines could produce more power with increased air and fuel flow rates.
Anyone who would simply run the supercharger faster will be disappointed to learn that supercharger drive ratios are also limited. Modern Top Fuel engines run with a 14-71 supercharger. This designation refers to the superchargers used on GM Detroit Diesel two-stroke diesels that were produced in a huge range of cylinder counts and engine displacements. Each two-stroke cylinder has a displacement of 71 cu in. The 6-71 supercharger is sized for a six-cylinder engine, and the 14-71 is for a 14-cylinder engine.
There are further restrictions to the supercharger specification to outlaw more modern developments. The rotors can be helical, but must be of a Roots-type design. High-helix designs are outlawed, and the helix angles may not exceed those of the standard GM 71-series rotors. The Lysholm-type screw superchargers that are popular in modern drag racing because of their significantly lower friction are also outlawed.
When screw compressors were first introduced in drag racing in the late 1980s, a Roots-type Top Fuel supercharger consumed up to 850 bhp in friction, and the new screw-type used 320 bhp to give the same flow rate and boost (2), giving an instant and very significant boost to useful mechanical output power.
For the 6-71 supercharger used in Nostalgia Nitro Funny Car, there are specific rules governing the dimensions of the rotor length, case length and rotor cavity diameter, plus the drive ratio from the crank to the supercharger. This combination of regulations is very effective in limiting the mass flow rate of air and thus potential power.
The 14-71 supercharger has a nominal airflow capacity of 233% of the 6-71 unit, yet the power output of the modern engine is proportionally more than that. The answer lies in the fuel. Nitromethane (CH3NO2) carries two atoms of oxygen, so pumping more fuel in for a fixed airflow also increases the supply of oxygen to the cylinder.
Fuel and fuel flow
Modern Top Fuel engines use fuel pumps with a capacity of 110 gallons per minute or more. The engines can’t use this quantity of fuel, so they return some of the fuel to the tank.
As Monise explains, “The biggest difference is the amount of fuel they can burn during a run. With our 21 gallon pump we have no returns to the fuel tank, so everything that goes through the pump goes into the motor to be burned. Modern Top Fuel cars run so much fuel that they can return a fair amount back to the tank and control it at every tenth of a second on the track.”
Ignition systems also play a part here. As Monise notes, “Top Fuel runs two 44 A magnetos with two spark plugs per cylinder, while we run one 12 A magneto with one spark plug per cylinder.” Multiple combustion initiation sites increase both the likelihood of successful combustion and its efficiency. The ‘stronger’ spark produced by the higher currents in the modern ignition system is more likely to produce a successful initiation of combustion.
Even in a run lasting only a few seconds, this kind of damage can happen. Sometimes a weekend can see more than one engine wrecked (Courtesy of Geoff Monise/Quarter Pound Nitro Funny Car)
What will be obvious with such huge quantities of fuel, even in a race series producing 1970s levels of engine performance is that the types of fuel metering devices that we are accustomed to can’t be used. Such engines rely on high volumetric flow-rate mechanical injection to pass these volumes into the cylinder. The NHRA regulations allow for a maximum of 24 injector nozzles in Nostalgia Nitro Funny Car
Nitromethane is really unusual fuel. Because it carries enough oxygen of its own in the nitro group attached to the central carbon atom, it can be burned without any oxygen at all. In dragsters it is usually run in very rich mixtures, which has the helpful effects of providing cooling and discouraging damaging detonation/pre-ignition.
There are various products of combustion depending on the air-fuel mixture used. Rich running keeps the engine cool because of the high heat of vaporisation, and also results in part of the visual and aural spectacle of this type of racing. Rich nitromethane mixtures have carbon monoxide and hydrogen as combustion products, which means that further combustion of these products is possible when more oxygen is available. When these hot gases are mixed with atmospheric oxygen at the end of the exhausts, the carbon monoxide and hydrogen combust.
In previous conversations about drag racing engines, I was told by noted supercharger and drag racing expert the late Norm Drazy that the cylinder pressure in a Top Fuel engine can be as high as 200 bar when the exhaust valve opens with combustion still not being complete. Even experts are unclear on what the combustion process is for nitromethane, with several possible combustion reactions being possible, involving different amounts of oxygen from none at all to five oxygen molecules to one fuel molecule. The rich combustion process means only part of the fuel is fully combusted, with all the carbon combining with oxygen to form carbon dioxide and all the hydrogen combining with oxygen to form water in the cylinder.
There is an interesting question about nitromethane and alcohol engines producing this level of power. Alcohol fuels are much less expensive: there are modern alcohol-burning engines producing greater output, although they can either run a more efficient screw-type supercharger or use a larger-capacity engine with a Roots-type supercharger.
Monise says, “Nitro is the fuel of choice because it makes more power than alcohol. We are allowed to run 100% nitro, but usually we run about 85%, mixed with alcohol”.
Why not 100% nitromethane? “The reason to run more or less nitro percentage is based on tune-up,” he says. “The more percentage of nitro we run makes the tune-up hotter, so it will tend to burn up pistons and such. We have found that about mid-85% has given us the best balance between hurting the engine and running very strong.
In this case, an engine strip between runs allows the one damaged piston to be changed (Courtesy of Geoff Monise/Quarter Pound Nitro Funny Car)
“Modern alcohol Funny Cars do run quicker, but they have a more efficient supercharger. They are also allowed modern ignition and fuel timers and they use a three-speed transmission while we run a two-speed.”
While the performance can be produced from an alcohol-fuelled engine, it would perhaps not produce the same spectacle and would no longer be true to the retro aspect of drag racing; a modern transmission and engine would be required. The original 1970s engines used nitromethane, so it is important to stay true to the original fuel, engine type, transmission and other aspects of the 1970s technology. The NHRA Nostalgia Funny Car rules specifically outlaw any fuels containing less than 65% nitromethane.
Working at the strip
The challenge of retro drag racing is not simply connected to the sourcing of suitable parts and producing a competitive power output. A degree of maintenance is required during a busy race weekend, and the level and regularity of ‘invasive’ engine work varies significantly.
In the UK, the amount of work on the engine is pretty limited for Hadfield, where his race time per day can be anything up to five runs; he has only to check the valve lash (clearance) after each run and change the oil and oil filter at the end of each day. After each meeting, there is some extra work, as he explains. “I remove the sump and check the big-end and main bearings, do a leak-down test to check for any cylinder leakage and reset the valve lash.”
On the other hand, Monise, competing in NHRA events, has much more to contend with. He says, “Races consist of three rounds of qualifying, with the top 16 cars qualifying. That makes it four rounds of racing eliminations.
“After each run, the motor is completely torn down to a bare block and crank. The rods and pistons are inspected and replaced as needed. Cylinder heads are checked and replaced as needed. They fill the car with oil and fuel and warm it up to check the timing and for any fuel/oil leaks before making another run. After warm-up, the valves are readjusted and final prep is done.
“When the car comes back to the pit after the run, the supercharger and manifold are removed as one unit by two crew members. While the top of the motor is being removed, there is another crew member under the motor who drains and removes the oil pan and begins checking the main bearings. He also removes the rod caps and pushes the rods and pistons up out of the motor once the two top-end crew members have removed the cylinder heads.
“The pistons, piston rings and bearings are all placed in a rack and carried into the trailer to be inspected and hopefully, based on wear, put back into the motor later in the weekend. We show up to the track with three complete rod and piston assemblies, which will get us through one day. There is also another crew member servicing the clutch during this time. A fifth crew member is using this time to clean and inspect the parts for wear and tear.”
A well-drilled team of mechanics and engineers can strip, inspect and rebuild a V8 at the drag strip between runs. Pistons and bearings are the most likely to need replacement (Courtesy of Geoff Monise/Quarter Pound Nitro Funny Car)
The whole procedure to strip, inspect and rebuild takes an incredibly short period of time, about an hour between runs, according to Monise. Doing this work so quickly in the open air at a racetrack necessarily involves concessions to cleanliness and not relying on the levels of precision and procedure associated with engine building in other racing formulae.
“The motors we are running were not built in a clean room, so they are not held to the tolerance specs that a 24-hour endurance or Formula One engine would be held to,” Monise says. “We can get away with a little more crudeness because we are inspecting during rebuilding after each run [which ends up being a total of 2 minutes between burn-out and run].
“We decide to change parts based on the wear and tear of the bearings, pistons and piston rings. If a piston is badly damaged, we can also replace a cylinder sleeve during this time. In extreme cases, if a bearing tries to spin and damages the crank, we will change short blocks between runs. We usually only have an extra short block, so this is to be avoided at all costs. We monitor the number of runs on rods and crank, and hopefully time them out.”
Monise uses his rods for a maximum of 20 runs, and his crank is used for a maximum of 60 runs.
There is clearly a lot of strip and rebuild work to do in the hour, which leaves very little time to inspect parts and decide whether any need to be replaced before their usual end of life. The fact that the team always carry spares shows that lifing components is not always an exact science.
Even with very experienced and well-drilled staff working on the engine, not everything goes to plan. “At the March Meet in March 2022 for example, we were runner-up and had damaged three motors in the process,” Monise says. “That is not normal, but the weather was quite tricky that weekend.”
Summary
The challenges in historic drag racing are very similar to those faced back in the 1970s, as well as those faced by modern competitors. Despite the cars and engines looking dated in appearance, the engines consist of new parts and so, providing a popular motorsport engine is used, the availability of parts does not cause problems. In fact, the only significant parts supply problems have been caused by issues concerned with the coronavirus pandemic, which have affected industry and life in general.
The rule book governing these classes of racing is a slim document (3), and has only a few effective rules that govern performance based on the supply of fuel, supply of air and ignition. Although the performance of the Nostalgia classes is some way behind the cars currently competing at the top levels of the sport, competitors face broadly the same challenges in terms of maintenance over the duration of a race meeting as their modern colleagues.
In the Top Fuel classes of Nostalgia drag racing, engines are still fully stripped, relevant parts visually inspected and measured and the engines rebuilt between runs. The well-drilled team staff can strip, inspect and rebuild and engine in around an hour.
As with many classes of motorsport, costs are significant and the measure of success of a class at any level of motorsport is the number of competitive entries to meetings over the course of a season. In this respect, nostalgia drag racing is in good health on both sides of the Atlantic.
References
1. Butcher, L., “Top Fuel Engine Power”, RET 90, November 2015
2. Ward, W., Focus article on Turbochargers and Superchargers, RET 51, December 2010/January 2011
3. NHRA Nostalgia Funny Car Regulations (downloaded santapod.co.uk/forms/NostalgiaFunnyCarRulesV1.pdf)
GEOFF MONISE’S 496 CU IN NITRO CHRYSLER HEMI ENGINE
NHRA Nostalgia Funny Car
90º V8
4.187 x 4.5 in = 496 cu in (8.128 litres)
6-71 Roots-type supercharger
85% nitromethane/15% methanol fuel
Aluminium block and heads
Ductile iron liners
Five main bearings, plain
Steel crankshaft, four pins
Steel con rods
Aluminium pistons, three rings
Pushrod; gear-driven single camshaft
Two valves/cylinder, one plug
50º intake valve inclination, 55º exhaust
2.45 in intake valve, 1.925 in exhaust
Distributor ignition
Port fuel injection
6.4:1 compression ratio
Maximum rpm, 10,500
SOME KEY SUPPLIERS
Block: Brad Anderson Enterprises (BAE)
Head: Alan Johnson
Liners: Darton
Liner coating: Darton
Crankshaft: Velasco
Rods: CP-Carrillo
Rod bolts: ARP
Pistons: CP-Carrillo
Piston rings: Clevite
Piston pins: BAE
Main bearings: Clevite
Big-end bearings: Clevite
Thrust bearings: Clevite
Valves: Manley
Valve seats: BAE
Valve guides: BAE
Valve springs: PSI
Spring retainers: PSI
Cam drive components: Casale
Camshafts: Bullet
Cam followers: Jesel
Cylinder head seal: Hussey
Fuel injectors: Enderle
Engine management: MSD
Fuel pumps: Waterman
Data acquisition: Racepak
Sensors: Racepak
Oil pumps: System One
Oil filters: XRP
Exhaust: in-house
Fluid lines and adapters: XRP
Materials: TMS
Fuel: Dale Pulde
Oil: Lucas
ANDY HADFIELD’S 598 CU IN ALCOHOL BIG BLOCK CHEVROLET
Altered class Nostalgia drag race
90º V8
4.63 x 4.5 in = 598 cu in (9.8 litres)
Roots-type supercharger
100% methanol fuel
Cast iron block, aluminium heads
Linerless
Five main bearings, plain
Steel crankshaft, four pins
Steel con rods
Aluminium piston, three rings
Pushrod; single chain-driven camshaft
Two valves/cylinder, one plug
2.35 in intake valve, 1.85 in exhaust
Distributor ignition
Port fuel injection
Compression ratio, undisclosed
Maximum rpm, undisclosed
SOME KEY SUPPLIERS
Block: Dart
Head: AFR
Crankshaft: Manley
Rods: Oliver
Rod bolts: ARP
Pistons: JE
Main and big-end bearings: undisclosed
Valves: undisclosed
Valve springs: undisclosed
Camshafts: Comp Cams
Fuel injectors: Enderle
Engine data analysis: Castleford
Oil pump: undisclosed
Exhaust: undisclosed