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Datsun 510 Rally Beater: Part 1

Introduction

Dave Coleman
Jul 16, 2002 SHARE

Inspiration can take many forms. For many, it's the soft red glow of a perfect sunset or the view from atop a high peak. For us, inspiration usually involves metal and internal combustion, and this particular time, it also involves rocks. The event that inspired this project happened at the Ramada Express Hotel and Casino International Rally last year (SCC June, 2000). We were covering the rally, as we have since the event started in 1999, which meant frantically running up and down the stage roads before and after each stage, negotiating with the stage police, sweet talking radio operators, and generally doing whatever it takes to put ourselves in the dangerous positions that reward us with the best photography.

Somewhere in the Hualapai Indian Nation on the edge of the Grand Canyon, we were following the sweep vehicle down a turnaround stage in search of a good spot to shoot the cars on their return run. Following the sweep vehicle gives you a unique perspective on a rally. From any other viewing spot, you get to see the victors, or at least the survivors, but the sweep vehicle is the filter, dredging up the stragglers, the unlucky and the cursed. Each wrecked or disabled rally car is approached with a sense of sympathetic awe. The natural fascination with the gruesome interaction of rock and machine is quelled somewhat by the realization that literally months of preparation had just come to a decidedly untriumphant end.

One of these wrecks was different. Protruding from a high-speed right was a partially buried rock on the right side of the road, a gap of about 100 feet, and then a white, first-generation RX-7 parked remarkably far up the left bank in a field of jagged, basketball-sized rocks. The left front strut was folded into the back of the wheel well, the fender was crumpled, and every one of the stock aluminum wheels was not just bent, but broken, with several large, jagged pieces missing from each one. This was all typical rally damage, but the defining difference that made this moment inspirational was the reaction of the driver. He was grinning ear to ear. In fact, he was downright giddy. The damage to his car was as much an object of fascination as a cause for regret. The secret of his peace of mind? His car was a beater.

Victory had not been ripped from his hands; he never had a chance in the first place. He hadn't come here for victory, he had come to have fun and by that measure, his rally was a success. He crashed only two stages from the end of the second full day of rallying, so he got almost all the sideways-sliding, dirt-thrashing driving he had planned on and because first-generation RX-7s are both abundant and cheap, it would be easy for him to fix the car. In fact, he had it running the next day.

Until this time, we had always concentrated on the exotic, big-dollar rally cars. The Lancer EVOs, Impreza WRXs and Audi Quattros make for much more exciting photography than 20-year-old Corollas, GLCs and Fire Arrows. But suddenly, we realized that for the price of a set of brake rotors for a Lancer EVO VI, you could buy a fleet of Plymouth Fire Arrows. Suddenly, rallying doesn't have to be expensive. Suddenly, every neglected piece of yard art in front of every trailer park is a potential rally car. Suddenly, that eyesore in the driveway has a purpose. It was this dramatic change of perspective that inspired us to finally go rallying.

With no budget.

Pick Your Beater Wisely
The first step in building a rally beater is picking the beater. Start with the wrong car and you could end up spending a Lancer-sized fortune on modifications and replacement parts. The most fundamental requirement for a rally beater is durability. If a car can't survive 200,000 miles of neglect on the road, it won't survive 10 minutes on a rally stage--especially on the rough, rock-strewn roads for which West Coast rallies are known. The second requirement is abundance. Try finding a new left outer tie-rod end for a 1976 Lancia Scorpion in Pahrump, Nev. on a Saturday night. Good luck. Finally, the beater should have some sort of motorsports history, or should at least share fundamental driveline and suspension parts with something that does. This ensures that at some point, somebody figured out how to make your beater fast and somebody else made race parts to sell to the first person.

For our rally beater, we chose the venerable Datsun 510. In our case, the choice was easy. The 510 was sitting in the driveway and the neighborhood association rules stipulated that you couldn't leave non-functional cars sitting on your property. For two years, moving and re-parking the 510 in a different position had been a weekly routine to ensure that nosy neighbors didn't declare the car dead.

Besides the obvious benefit that it was already there, the 510 is exceptionally durable, having a long and illustrious competition history both on the track and in international rallies. Though more than 500,000 510s were sold in the United States, they are rather rare today, more than 27 years after the last one was made. The 510's saving grace, however, is the fact it was the foundation on which every Datsun for the next 10 years was built. In other words, there are plenty of non-510 parts cars out there ready to give themselves to our cause.

Though perfect for our purposes, 510s are too rare to be considered a viable rally beater candidate unless you already have one. Far more abundant are the old '85 to '87 AE-86 chassis Toyota Corolla GT-S and the '79 to '85 Mazda RX-7. Both cars are durable, rear-wheel drive (it's actually debatable whether this is an advantage), fantastically abundant and have enough years of competition behind them to make critical parts like shocks and limited-slip differentials easy to come by.

Before embarking on your rally beater journey, it's always wise to attend a few local rallies and look for used rally cars for sale. Used beater rally cars have two advantages over the kind you build yourself. First, they are inevitably less expensive. No matter how much you cheap out, the nickel and dime parts will eat up your budget faster than you can say "metric bolts are too expensive." Every rally car must put at least one marriage on the rocks and must demand a second mortgage on at least one house. Most used rally cars already have this out of their systems. The second advantage to buying used is the fact that you have no emotional attachment to the car. After six months of careful preparation, you might be reluctant to fling your baby sideways at a tree, but you couldn't care less about that ugly piece of crap that somebody else built. Crappy rally beaters can be had for around $3,000 to $4,000, and exceptionally well-prepared, almost-new rally beaters often trade hands for as little as $6,000 to $7,000.

OK, you've heard the advice, but you're still going to build it yourself. That's how car people are. Consider it a self-financed payment plan. If you spend it piece-by-piece, that $7,000 you don't have won't hurt nearly as much, right? We knew better, but the 510 was begging and we had to give in. We have learned many valuable lessons in the process of converting our car from eyesore to rally eyesore, so without further delay, here is what we have learned.

The Engine
The first thing you are going to want to do is make a ton of horsepower. Don't bother. If your beater runs, just leave the engine stock. Doing so may allow you to run in some sort of stock or production class, depending on the regulations of your local sanctioning body (or the SCCA if you are planning on collecting national points). More importantly, this will save money to spend on more important things. If you aren't already an experienced dirt driver, and odds are you aren't, starting out with relatively little horsepower will allow you to concentrate on developing the skills necessary to drive sideways smoothly and consistently in the challenging conditions you are likely to encounter. Leave horsepower for later.

If you have to build a new engine just to make the car move, or if you simply plan to ignore our advice, concentrate on building a flexible, torquey engine rather than a maximum horsepower screamer. When you drive in the dirt, the majority of your steering is done with your foot. If you have a broad powerband, you will be able to modulate the throttle to control your attitude in a corner. If dropping below 4000 rpm means dropping out of the powerband, you could have a very difficult time controlling the car in slower corners.

Our beater ran, but had an embarrasingly under-powered, 30-year-old 1.6 liter and a senile, three-speed automatic. Don't even try to rally with an automatic transmission. Remember throttle control? The disconnect between your right foot and the drive wheels that an automatic creates will put you backwards off a cliff in no time.

Luckily, in our case, we had an engine sitting around. Remember that thing about every other Datsun being a donor car? Our engine has an L18 block, crank, and rods from a 610, an L20B cylinder head from a 200SX, pistons from a 280ZX, an intake manifold and dual Hitatchi SU carburetors from a Japanese-spec SSS 510, a Datsun Competition rally cam, a stock 510 flywheel, a clutch from a Datsun 2000 Roadster and a five-speed transmission from a 280ZX. The engine cost about $1,000 to build 10 years ago, the transmission cost $175 as a Japanese import and the carburetors cost $250 at a Datsun club swap meet. Since the engine had 10 years and a lot of mileage on the clock already, let's call it a $400 used engine, maybe $500 in a pinch. Since the car cost $500 in the first place, we have a $1,000 car so far.

Putting this Frankenstein engine in the car took literally hours of work. Two of those hours to take the old engine out, and about three more hours to put in the new one. Old Datsuns are remarkably simple cars. Since the 280ZX transmission is longer than the 510 automatic, we had to bolt the transmission crossmember in backwards. This only works if the crossmember came from a car with an automatic, so lucky us. We also had to cut a hole in the transmission tunnel to let the shifter poke through. Finally, the driveshaft had to be shortened, so we made some quick measurements and dropped the driveshaft off at a local driveline shop. One day and $88 later, the driveshaft was the right length, balanced and had fresh U joints.

Making the clutch work also required buying a brake and clutch pedal from the junkyard, a master cylinder and bending up a custom hydraulic line for the clutch circuit. This cost another $50 or so, but it all bolted in.

A custom-bent 2.25-inch exhaust pipe cost $120 at Ace Muffler, and we found a free muffler sitting in a junk pile at Jackson Racing. Not being picky saves a lot of money. Having the exhaust custom bent allowed us to conveniently place the flanges to allow the middle of the exhaust to be removed for servicing the rear suspension.

Dialing in the engine was a rather arcane combination of seat-of-the-pants and dyno tuning. Get ready for a lesson in carburetor history. Fuel mixture on Hitatchi SU carbs is adjustable by means of a hand-cranked knob on the bottom of each carb. We simply leaned it out until it started to stumble at cruise, then richened it up a quarter turn. The engine still seemed happy at wide-open throttle, so we left it at that.

Ignition timing was a little more difficult. The engine seemed happiest with a huge amount of initial advance. About 30 to 35 degrees seemed right at idle (that's about 40-45 with the vacuum advance hooked up), but at high rpm, it would start to ping. The 280ZX pistons gave us 10.0:1 compression ratio and the open combustion chamber of the 200SX head has absolutely no quench area and consequently, relatively poor knock resistance. The mechanical advance was too much for the engine as it sat. If you remove about four phillips screws, the vacuum advance plate comes off, dual points and all, and the mechanical advance mechanism is in plain view. There are two weights, two springs and a plate with two slots in it. As centrifugal force causes the weights to move outward against the resistance of the springs, tabs on the weights slide in the slots, advancing the breaker point cam. Got it? So to reduce the total amount of mechanical advance, the natural solution is, of course, JB Weld(R). We smeared some of the metallic epoxy goo into the slots, let it harden, and filed the slots to what appeared to be an appropriately shortened length. After that, the car ran great.

After this fabulous display of shadetree engineering, we took the car to Jackson Racing's Dynojet, stuffed a wideband O2 sensor probe up the tailpipe, and started using science. Science told us we already had a relatively safe 13.0:1 air/fuel ratio at wide-open throttle and we were making a whopping 90 hp. After pushing the envelope with ignition timing, we were able to get that all the way to 95 hp and 103 lb-ft of torque. The important thing to note, however, is that torque peaks around 4000 rpm, and the powerband is nearly flat from 5500 to 7000 rpm. This engine is exceptionally flexible for a relic, and 103 lb-ft of torque is plenty to spin tires in the dirt.

There is actually a critical step in the middle of this tuning process where Project Rally Beater took the honors as the lowest-powered project car in SCC history. For a period of several months, the engine was installed in its current state of tune, but due to a sudden bout of laziness, it was still using the stock, 1.5-inch exhaust system. [Editor's note: This was the state of tune it was in when, for our "Rallycross Smackdown" story in August 2000, it beat both Project 323 GTX and Project Impreza at a local rallycross event. OK, yes, there was a little issue with the timecards, and yes, technically, the 510 was more than 30 seconds behind either of the other two cars, but that's just a matter of timing.]

Anyway, the point is that for that period of time, we were making 77 hp at the wheels, setting a new low we hope never to see again. Even with that 77 hp, however, the car still had enough power to handle properly in the dirt and worked well enough to allow us to concentrate on other parts of the car. If you can manage even 77 hp out of whatever beater you choose, move on and deal with another part of the car first.

Cooling System
Even with power output that would shame a lawnmower, the stock cooling system will probably be inadequate. There are two reasons for this. First, your car is a beater. The radiator is clogged from decades of neglect, and is critically undersized due to the cost cutting that made your beater affordable in the first place. This is true almost without exception, no matter what beater you have. The possible exception being a Volkswagen Rabbit, Golf or Jetta, which will only have the neglect part to deal with. Their radiators are so generously sized that they are often used to solve the cooling problems of less fortunate cars.

The second reason you will need cooling help is that you won't be going very fast, but your poor little 77-hp engine will be working its heart out. If you stick with the stock cooling system, your first rally will inevitably start with a twisty, 15-mile uphill stage at 6,000 feet of elevation when it's 100 degrees F. When we started beating on the 510, it already had been upgraded to a triple-core radiator with an electric fan and even that was hopelessly inadequate. When practicing on 15-mile, uphill roads in 100 degrees F, it would overheat after about three minutes of driving.

The solution, obviously, is to find something much bigger. There are different routes you can take, including swapping in a radiator from the aforementioned Volkswagens. However, in addition to making sure the radiator will fit in the front of your car, you should also make sure the hose outlets are at least somewhere close to the right location. Even if you can't stick with the stock hoses, you at least want to avoid having hoses running back and forth across the front of the engine compartment. These long hoses are a potential point of failure that should be safeguarded against, if at all possible. Rabbit radiators are a common swap into 510s like ours, but one hose has to cross over, so we decided to look for something else. After determining the biggest rectangle we could fit in front of the engine, we went to Fluidyne's Ontario, Calf. headquarters and started looking at what it had. Its closest production radiator was one for a Mustang, but the hose outlets were not ideal. Then we stumbled across an extra Ford Focus radiator that had been made for Ben Ma's 800-plus-hp Focus drag car. Dimensionally, it was identical to a stock Focus radiator, but its cooling capacity was dramatically improved. It fit perfectly.

It is possible a stock Focus radiator will cool a 77 or even a 95-hp rally car sufficiently, but the only way to be sure is to try and possibly fail. The cooling system is one of the few places where splurging on our beater seemed worth while. An insufficient cooling system will end your rally and could destroy your engine, costing far more than a good cooling system would have cost in the first place.

To mount the radiator, we set it in the engine compartment and noticed it sat over a flat area. Supporting the weight of the radiator was as easy as buying a set of doorknob stoppers and screwing them to the car below the radiator. With the weight supported, all that was necessary was to keep the radiator from tipping forward or backward. This was accomplished by cutting open some rectangular aluminum tubing and lining it with 1/8-inch thick foam padding. These foam-lined C-brackets were then bolted to the core supports. The electric fan was mounted to two crossbars that connected the C-brackets behind the radiator. Since it is worth almost as much as the car itself, we felt it was imperative that the radiator be protected against damage by mounting it as gingerly as possible.

While the hose outlets were close to the right locations, they were still far from perfect. The stock hoses missed by several inches both on the top and bottom. To span the gap, we used four 90-degree elbow hoses from Thermal Flex. By splicing together two 90-degree hoses, you can connect just about any two points, but if that doesn't work, they also have other bends available. We originally spliced them together with plastic hose savers from the local auto parts stores. These were essentially very short pieces of plastic pipe with barbed ends. Despite the fact they were designed to work in a cooling system, they quickly softened from the heat and shriveled up under the pressure of the hose clamps. We used stainless-steel tubing to replace them.

The Fluidyne Focus radiator also doesn't have a radiator cap, so we had to relocate the cap to the engine. This is not at all an unusual problem when swapping radiators. If there is no other option, you can put the radiator cap in the middle of the upper radiator hose, but we were able to use a thermostat cover from a Datsun Roadster that had the cap on the engine and had the same thermostat as our engine. Wherever you put the cap, try to have it at the highest point in the cooling system so air doesn't get trapped in the top of the system. There is some trapped air space in the top of the radiator, but Fluidyne addressed that issue by adding a pipe plug to the top of one of the end tanks to bleed the air from the system.

The see-what-fits-and-use-90-degree-hoses method will work for any beater, but if your beater is a first-generation RX-7, you should also put some effort into the oil cooler. Some RX-7s had large, front-mounted oil coolers, while others used a small heat exchanger under the oil filter. The front-mounted oil cooler works best, and can be retrofitted to the heat exchanger cars. The oil cooler must be protected from rocks and must be able to get clean airflow. The oil lines to the cooler are also frequent sources of leaks and the factory lines are expensive. If you take the old lines to a hydraulic supply shop, they can re-use the ends and replace the flexible hose section for far less money. This will also allow you to relocate the oil cooler for better protection from rocks.

It was more work to install the radiator than it had been to install the engine, but the work was well worth it. On the same roads that previously overheated the car in three minutes, the car can go 40 minutes at full throttle and never get hotter than 190 degrees. On the road in mild weather, you can actually see the thermostat open and close if you watch the temperature gauge closely.

Next
Now, we have an overwhelming 95 hp, a driveshaft twisting 103 lb-ft of torque, a cooling system that can handle our abuse and a long way to go. Next time, we'll cover building a suspension that can handle rocks, dirt, jumps and all that mess, getting the safety equipment right and keeping the electrical system from melting down.

How Cheap Can You Rally?
Car: $500
Engine: $500
Exhaust: $120
Clutch Mechanism: $50
Driveshaft: $88
Radiator: $435
Hoses and brackets: $125
Total So Far: $1818
Find More About Rallying
California Rally Series
www.californiarallyseries.com

SCCA
www.scca.org

International Rally Sport Group
www.rallyusa.com

Ben's Rally Page
www.bensrallypage.com
Sources
Fluidyne
4850 E. Airport Dr
Ontario, CA 91761
(800) FLUIDYNE
www.fluidyne.com

Thermal Flex
(714) 690-3840
www.thermalflex.com
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By Dave Coleman
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