Here's The engine we built...
Here's The engine we built in the last installment of our project. While in the process of building it, we went on a lightening rampage with the rolling chassis.
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.
Here Is the Comp Cams Special...
Here Is the Comp Cams Special at FNO Race Cars in Concord, North Carolina, ready for rollcage work. With the front removed, you can see the lack of 5-mph bumpers. This saved about 40 pounds right off the front. On a GT 5.0, the weight savings here is almost double.
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.
FNO's Back-half rollcage included...
FNO's Back-half rollcage included a cross-frame seatbelt anchor bar and diagonal plus rear shock tower struts and support for the rear suspension pickup points. All this also tied into the previously installed subframe connectors.
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.
We Used a 31/44-inch-square,...
We Used a 31/44-inch-square, thin-wall steel tube to make up the top and bottom rail plus the middle diagonal (top arrow) of our new dash. When this was tied into the floorpan with a 31/48-inch thin-wall tube (bottom arrow), the entire assembly became rock solid.
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.
With The top and bottom dash...
With The top and bottom dash tubes placed as seen here, remounting the stock instrument cluster became a breeze. The cluster sits on the square tubes resting on the ends of the panel screw bosses (red arrows). One fixing bolt on the top RH side and a bridge clamp (yellow arrows) plus a couple of stacks of washers gets the job done in a secure if not stylish manner.
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.
This Cobra Sportsman seat...
This Cobra Sportsman seat not only offered good comfort and retention around corners, but also only weighed in at 22 pounds. That's less than half a stock seat.
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.
Here's One of the BFGoodrich-shod...
Here's One of the BFGoodrich-shod wheels acquired for our racer. The tire choice here is the key factor. The BFG Comp T/A KD radials (from Tire Rack) work well on a 5.0 with less than an optimal road-race suspension.
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.