Muscle Mustangs & Fast FordsProject Vehicles
Budget Ford Mustang Build - Back-To-Basics Budget 5.0 Buildup Part 4 - Tech
Here's How To Make A 302 Run Like A 347-At Zero Cost.
Last Month we covered the build of the Edelbrock-headed, Comp Cams-equipped, $2,289 engine you see here. While the engine build took place, a considerable amount of grunt work was being carried out by three University of North Carolina at Charlotte (UNCC) students on the rolling chassis.
In case you've just picked up on our build series, let us make one thing clear. We originally decided to try and run low-10s for $7,000. As the project progressed to this point, we discussed many theories and have attacked many ways to go fast on the cheap. The whole point of this car, or any budget-minded Mustang, is to go as fast as possible for as little as possible. The worst enemy a race car has is weight, and that's largely what we're centering our efforts around this month.
Massive Mass Reduction
Assume, for the moment, a nominal rear-wheel horsepower figure of 320 and 320 lb-ft for our project car with its new engine. If this was in a typical stock weight car of 3,200 pounds, it would have a weight-to-power loading of 10 pounds per horsepower and 10 pounds per lb-ft. This means, in round terms, that every 10 pounds sucked out of the car is equivalent to an increase of 1 hp and 1 lb-ft at the rear wheels. Most importantly is that the weight reduction feels exactly like an increase in torque occurring throughout the entire rpm range. If you're having difficulty imagining what that feels like in terms of extra performance, think of it as having the same effect as an increase in cubes. For our Comp Cams special at its current weight and displacement, for every 10 pounds of weight reduction we gain about the same effect as an increase of 1 ci in engine displacement.
The question now is, how much weight can we remove without spending an additional dime? Let's start with the engine, as a sizable amount of weight was removed in the process of hopping it up. The Edelbrock heads were exactly 50 pounds lighter than the stock iron heads. The intake manifold saved a few more-in all, an estimated 75 pounds was shaved off the engine weight due to dispensation of unwanted smog gear and the like. So not only did we gain power by hopping-up the engine, but the bonus of weight saving was equivalent to another 7.5 hp and 7.5 lb-ft of torque. This weight savings came right off the front where a 5.0 is carrying far too much of its total weight for either an optimal dragstrip launch or its best road-course handling. Just for the record, our project car started off life with 56.9 percent of its total weight on the front wheels. That's bad enough, but consider our car did not come equipped with A/C. A car so equipped would have as much as 57.5 percent on the front wheels. Do you think this in any way is going to be conducive to performance? Not a chance.
With the original engine out, the guys tore into our 5.0 and gutted it. Everything that had nothing to do with safety, going, stopping, and cornering was dumped. Well, almost everything. At the front, the 5-mph crash bumpers were removed but left intact at the rear to help balance out the adverse front-to-rear weight situation. As you can see from the nearby pictures, the term "gutting" is hardly an exaggeration. Where we stopped short on this session was at the door internals. We were not yet in a position to buy materials for plastic windows, so the original crash-protection door bars (about 15 pounds apiece), door glass, and manual window winders were left in. We plan to tackle the doors as a separate project as we see an estimated 30 pounds a side coming out.
With the front-crash-protection stuff out and the entire interior trim/dash gone, we moved on to the next step. Although the car came with a rudimentary rollcage, it was, at best, only OK for a drag-race deal. We needed to do some serious upgrading here, especially for road-course use. As it happens, bending up and welding cages is something your author's shop is ill-equipped to do, but his friend Charlie Barham, the boss at FNO Race Cars in Concord, North Carolina, is at the other end of the spectrum. Charlie's company builds late-model stockers, maintains and repairs Busch cars, and installs Cup Car-style cages into road-race cars. Because he's set up to do the job in a quick and speedy fashion, the cost of getting a pro-style cage is far from the vast expense you might think it to be. Our plan was to do the cage in two stages.
First, the existing cage would be largely cut out and replaced by what would eventually be the middle and back half of a full NASCAR-style cage. At the speeds initially expected, this would be more than adequate for the dragstrip. The second phase of cage construction would happen before making any serious foray onto road courses. This would include tying in the front suspension to the rest of the rollcage. This would leave us with a stiff chassis, not the flexi-flyer that the 5.0 is stock.
As far as performance is concerned, Charlie's rear cage construction is more than just a safety device as it ties the shock towers and rear-suspension pickup points to the rest of the body shell in a positive manner. I've heard from several industry drag chassis experts that this move, on a nominally 11-second car, is worth close to a 11/410 reduction in the quarter. Cost for doing this work is $300, but yours may be more or less, depending on what's currently there and what material is used for the cage construction. Ours was done in 4340 so, with the removal of most of the existing mild-steel cage, our considerably more extensive cage added little or no additional overall weight to the car.
The interior gutting process included getting rid of everything related to the dash and shifter console. All that was retained was the actual instrument cluster. The plan was that down the road we would dump the stock instrument cluster in favor of a nice set of Auto Meter gauges that would include a big 8,000-rpm tach. For now, the stock 6,500-rpm tach would do just fine.
The basis of the new dash would be a couple of lengths of 31/44-inch, thin-wall steel tubing strategically placed so as to support the stock instrument cluster. As you can see in the nearby pics, the top tube is bent to a large radius to match the lower edge of the windshield. This and the fact that we spaced out the lower support bar from the door pillar by about 3 inches will allow us to install a simple but smart looking dash panel later in the game. This will cover all our wiring and serve as a mounting surface for the new instruments when the time comes.
Going this tubular route not only was simple to do, but it also allowed an easy install of the original instrument cluster.
At about 45 pounds, the stock seats are heavy but also entirely inadequate when it comes to holding the driver in place during high-g's cornering. Decent race seats need not be that expensive, but we're trying to be real cheap here. A friend who is rebuilding his 5.0 into a big-inch blown car swapped out his Cobra Sportsman seats for one of those super-trick $1,000 Butler seats and offered us his "as new" seat for 75 bills-we took it. Not only was the price right, but the seat was also a functional fit for four out of the five of us likely to drive.
Here's the simple plan for the wheel/tire department: one set of wheels/tires for road racing and one set for the dragstrip. Most of you following this build are going to do one or the other although there is nothing stopping a road-race car from making a foray onto the dragstrip. The price for racing a pure road racer on the strip is a lackluster launch. On the other hand, your drag car will need a lot of work to make it safe even on a road course. Our plan is that we set up the car for road racing from here. When we go to the strip, the road-race wheels and tires will be replaced with drag-race items. The front (and heavy) antisway bar will be removed and the car raised about 2 inches for better weight transfer.
The wheels we had were far from what we wanted. We managed to pick up a set of used wheels and tires from Atlantic Racing in Charlotte for $150. The Goodyear Eagles and the wheels had 90 percent of the tread still in place so were sold leaving us with a set of wheels for only $75. A pair of these would be used for the drag-race setup. But more on the drag wheels in a later issue.
For now, the focus is on wheels and tires to get us around a road course. Here, luck was favorable once again. A set of four-lug alloy wheels and the required spacers to install them (they were originally intended for FWD applications) that your author sold over a year ago to a prospective racer never got used. That racer lucked out by landing a five-lug deal complete with brakes, and so on, so the wheels became available again. Your author bought them back at quite a bit less than he had sold them for because the spacers that went with them were nowhere to be found. What the heck, how much can a set of spacers cost? To our near horror, we found that spacers that push out deeply backspaced wheels and convert the four-lug 5.0s 411/44-inch PCD to 411/42 are far from available and also far from cheap.
Fortunately, we were able to uncover a near secret and closely guarded source in California that makes custom spacers for the wheel and tire shops. This company (check out the Web site at www.trailsport4x4.com) made up some billet (not cast) adapter/wheel spacers at an almost unbelievable cost of $160 for all four. Although the cost varies for custom-made stuff, be aware that the price of these was almost half of some of the other companies we checked out. Now we were in a position to use the wheels and BFG tires.
The main items on our agenda are the battery and a master cut-off switch. What was done here comes under safety and performance. First, the battery location was moved from the front to the back to help weight balance. Secondly, a dry cell-style of battery was chosen.
In this instance, we used two of Performance Distributors' Dyna-Batt units. The reason for two batteries was because of the electric water pump and no alternator. These batteries are about half the weight of a regular battery and provide high initial cranking voltage, which is great for starting.
A Dyna-Batt from Performance Distributors costs $119-and that's on-sale. We realize this is a little more expensive than a regular battery, but as such we have added $240 into the cost breakdown. If you are following this build, you will need only one battery, and the price difference to ensure that no acid will fly around the interior of your car in the event of a crash is well worth the difference between a Dyna-Batt and a $50 battery. If you are interested in drag racing only, then instead of making up a battery-retention system as we did, use a Mr. Gasket battery box kit. This comes with the box, all the cable you will need, and most everything else.
Suspension mods for a 5.0 come under two distinct headings: those that seek to stabilize pickup/pivot points on the suspension so they don't move and those that are intended to improve the geometry. Before you can do too much to the geometry, it's necessary to make sure the pivot points stay where they should be. Rubber is good at isolating road noise, but its inherent flexibility is not so good at keeping the geometry consistent.
We will address the excessive compliance of the stock rubber bushings. The simplest and most effective way is to use Energy Suspension's urethane bushings. These work well on the track while still being more than civilized for the road. Remember the supporting project car that owner Jason Peck is doing alongside our project? We had him install a set of Energy Suspension bushings just to get a second opinion. Jason told us, "It's almost like going from night to day." Your author is glad he felt that way because that's about what his response was when he first installed some of these a few years back. These days, the results are likely to be better because the cars being so equipped are having older, and consequently softer, bushings replaced by the Energy bushings.
Installing these bushes is straightforward enough but can be somewhat time-consuming unless you have all the right tools in hand. It can be done in the driveway over a weekend, but you'll need some tall jackstands, and an air-impact wrench will certainly make life easier. A special tool is needed and can be rented for a fully refundable $100 deposit from the good guys at AutoZone.
In racing, the real moment of truth comes when the car rides the dyno or goes to the track. Such was the case with our Comp Cams Special. Tests were done at Custom Performance late one night. Essentially, we made one run and found the mixture to be really lean. We aborted the run at 4,000 rpm as the average mixture ratio recorded was a thread-bare 17:1 instead of the 13:1 we were looking for. That was the bad news. The good news was that in spite of this way too lean condition, the engine still cranked out over 330 lb-ft of torque as seen at the rear wheels.
That's about 10 percent above what is typically seen by a warmed-over and optimally calibrated engine (which ours essentially is) with bolt-on heads and a moderate street-cam upgrade. The prospects of our engine producing good results when the mixture is fixed and the timing optimized are, at this point, looking extremely good.
Now about this time some of you knowledge-able guys are going to be asking what happened to the 5.0's famous ability to correct the mixture and thus compensate for engine mods. Well, that ability is still there, but obviously there's a problem with the hot-wire sensor in the mass airflow unit. Whatever it may be, this is causing it to read less air than is really passing through.
This could actually play into our hands and save us a bunch of cash. Here's the deal: The stock injectors deliver 19 pounds of fuel an hour at a shade under 40 psi. At a brake-specific fuel consumption of 0.45 lbs/hr/hp, the most power the injectors will allow the engine to deliver before being maxed out at 100 percent duty cycle is 338 hp. That's assuming everything is right on the money. In reality, it's likely to be a little less than that-but no matter, this capacity puts the injector right on or just over what's needed for fuel flow for our engine as it's expected to peak at about 320 flywheel horsepower. What we can do is up the pressure supplied to the injectors. Normally this would be only a fine-tuning measure but because of a fault in the system, we can use more pressure to not only fix the mixture ratio but also-at this stage at least-up the injector capacity to stave off the need to spend relatively big bucks on bigger injectors. A little math here shows that to get the mixture to 13:1 will call for the fuel pressure to be increased to about 64 psi. This will make the injectors good for 386 hp. With the pressure number in mind, the next move was to check Accel's catalog for an adjustable pressure regulator. When that arrives, we'll get back on the dyno and check out the results.
On the Scales-the Final Verdict
As can be seen from the nearby photo, our car is beginning to look a little more like a decent (at this time) road racer. We still have brake upgrades and shocks to do, but that's for an upcoming issue. Right now the question here is, how much have we lightened it? We had anticipated eliminating some 280-300 pounds from the car, but our efforts here came as a pleasant surprise to us all. The weight, less driver, dropped from 3,127 pounds to 2,692 pounds, for a savings of 435 pounds. In round terms that's a reduction of 14 percent. That means our 302 will appear 14 percent torquier, and that equates to about what you could expect from installing a 347-inch motor in place of the 302 and leaving the weight as is.
Dropping all that weight cost us nothing more than about six cans of spray paint to cover the marks made while scraping off the sound-deadening goop that Ford lathers onto everything under the carpet and upholstery. As good as that is for more go, it has even bigger implications on stopping. Taking out that weight means more brake for the weight involved. The big 13-inch disks normally used cost more than our budget at present allows. But taking out the 435 pounds means the brakes will now react as if the size has been increased from 11 inches to 12.4 inches, and that is one big step in the right direction.
If we could get the weight of the car down another 160 pounds, the brakes would have the same swept area per pound of car as 13-inch ones on a stock-weight car and would brake about as well-if the calipers were up to the job, that is. As it happens they are not, but we'll address that in the next installment by showing how to get close to 50 percent more clamping force out of some retrofit low-cost calipers. Couple this to some good brake pads, sensibly priced slotted rotors, and budget high-temp brake fluid, and we'll have a brake upgrade that, though still not as good as 13 inchers, will, for a fraction of the cost, be pretty awesome.
OK, back to the weight issue. Take a look at Fig. 1 showing the before and after weight distribution with a 200-pound driver in place. Although a stack of weight came off the front of the car, so much came out of the interior that the weight bias front to rear favored the rear by only 0.6 percent more than when we started. This is in spite of the fact that we moved the battery back to the trunk and left in the rear crash-absorbing bumper. The truth of the matter is that though we sucked a lot of weight out of this car, there's still much that can be done in this direction. A glass hood and door lightening could amount to another 75 pounds removed. A tubular K-member and tubular front A-arms would take close to another 100 pounds off the front. Plastic windows and a glass rear deck can account for about another 100 pounds. As far as lightening goes, we're not done yet, but from here on, it's likely to cost money.
Regarding the power-to-weight ratio, if our car hits 300 at the wheels it will run like a stock weight car having 342 rwhp. To us, that's the same as a gift of 42 free horsepower. In terms of performance, the weight reduction alone will be worth 0.4 and 5 mph in the quarter with a stock engine. With the 100 or so extra horsepower our engine makes, we should be looking at a fast ride. Given the tires, we should be able to run in the bottom of the 12s in the quarter with trap speeds in the region of 112 mph-and we still have the Zex nitrous kit in hand.
OK, now for the cost to date: As you see the car in the nearby photo, we spent $6,579.