1975 Chevy Laguna - The "X" Factor
We Go For The Full NASCAR Vibe With An X-Pipe, Flat Oval Tubing, And Side-Exit Exhaust From Dr. Gas.
From the November, 2009 issue of Popular Hot Rodding
By Johnny Hunkins
Photography by Johnny Hunkins
In Stock Car racing, every last fraction of a horsepower matters-and that's why you see an X-pipe from Dr. Gas on every single Cup car in NASCAR. Although the exact science of why they work isn't fully understood, we do know this much: When any given exhaust pulse arrives at the "X" juncture, the pulse expands along both available paths. In doing so, a negative pressure wave travels back to the exhaust port, which aides in exhaust scavenging. Balance pipes, sometimes called "H" pipes, function similarly, however, the effect is diminished due to the balance pipe's smaller diameter and the added bends the gas flow is subject to.
Before Lang could start on...
Before Lang could start on the Dr. Gas exhaust system, we needed a custom double-hump trans crossmember. Our old crossmember was a single-hump bar for a Turbo 350, and we now had a 700-R4 with duals. Here, Lang Paciulli, of LP Racing, has cut a 6-foot length of 1.25-inch diameter, 0.083-wall chromoly pipe, and is making some bends.
After thinking long and hard about the exhaust options for our '75 Chevy Laguna (Project Talladega), we decided that a no-holds-barred NASCAR-style exhaust was what we wanted. We liked the idea of maximizing our power just like the big-name racers, and the look would be a perfect fit for our NASCAR-themed project. Moreover, with a solid-roller 408ci small-block lurking underhood, we figured the sound alone would strike fear in the sport compact crowd, and it has so far turned out to be a great deterrent with no takers yet.
When we called Dr. Gas to sell them on the idea, we were pleasantly surprised to find out they had been following Project Talladega since the start. They were waiting for our call, and had a recommendation for our Laguna already picked out. Just to be clear, there is no "bolt-on" side-exit exhaust kit from Dr. Gas. You buy components that you will have to fabricate into a unique system. When you receive your shipment of Dr. Gas components, you will have the option of building the system yourself, or bringing it to a shop. In either case, the cosmetic result you get will depend on the work you put into building it.
Lang is sizing up the crossmember...
Lang is sizing up the crossmember so that it aligns with the existing frame bolt holes while providing necessary clearance for the dual exhaust. This is an iterative process where the crossmember was bent repeatedly to arrive at the ideal shape. As a chassis builder, this is one of Lang's sharpest skills.
Straight from Dr. Gas's "NASCAR" parts bin, we received a universal 3-inch X-pipe made from oval tubing (part No. U3O, $399.95). The Dr. Gas folks matched this to a pair of 3-inch Street Rod Boom Tube mufflers (part No. BTM3, $550.90). Looking more like flat, side-exit exhaust tips than mufflers, the Boom Tubes are essentially open, with spin traps welded inside them to mitigate some of the sound. They are loud, so be forewarned that you may run afoul of the local gendarmes if they don't fancy your automotive style. As fate would have it, we drove our finished Dr. Gas exhaust on the Riverside, California, freeway during a Harley rally, and suddenly found ourselves cruising in the midst of 15,000 wild hogs. We got a big thumbs-up from all for two reasons: our satin black paint fit right in with the biker vibe, and because we were still the loudest thing on the highway. The scene could easily have been an outtake from a Mad Max movie.
Building an exhaust system like this requires special fabrication skills, and for that we turned to LP Racing of Upland, California. The "LP" in LP Racing is Lang Paciulli, who specializes in race car fabrication and TIG welding in particular. Lots of shops do welding, but it's MIG for the most part. For those shops, welding is an unpleasant necessity, but Lang's interest in TIG welding borders on compulsive. If two metal objects need joining, chances are Lang will TIG weld them-with a smile on his face. As a result, it's no surprise that he's good at it. Lang's TIG skills are known throughout southern California, and like many others, we sought him out for our Dr. Gas project.
After cutting the crossmember...
After cutting the crossmember to the proper length, Lang cut a flat section where it would mate with the frame.
We're skipping a few steps...
We're skipping a few steps here, but the summary is that Lang is TIG welding a flat tab on the crossmember where it meets the frame. This tab has been shaped to fit the tube, and has a nut welded to the inside so that a bolt can be threaded into it from under the car. The placement of the tab and the nut has been precisely located with direct measurement from the Laguna's frame.
A chassis builder by trade,...
A chassis builder by trade, Lang has a multitude of generic brackets and gussets lying around his shop. He found one in particular that with only slight modification worked well as a trans mount. Here, Lang is checking the fit, then he'll tack weld it in place.
For a TIG job like ours, Lang charges about $350, which doesn't include the parts or the labor to construct our custom double-hump transmission crossmember. Lang and Dr. Gas both say that TIG welding isn't a necessity for this operation, but it's Lang's specialty, and at that price, we decided to go with the flow. It took about six hours to build our Laguna's exhaust system with the parts provided by Dr. Gas. When the labor charges are added to the cost of the Dr. Gas components, our one-of-a-kind side-exit system cost around $1,330. If you need to extract the maximum power potential from your engine, and you like the visual and audio shock value of a side-exit race system, that price isn't out of line. (If it were a piece of high-end sculpture, you'd pay five times the price for it.) Next month, we'll be installing a brand-new, bolt-in steering box from CPP that has transformed Project Talladega's handling, so stay tuned.
Lang TIG welds the transmission...
Lang TIG welds the transmission brace to the crossmember. While most shops prefer to MIG weld because it's easier, Lang prefers TIG because the welds are stronger (if done correctly) and they have a nicer cosmetic appearance. Since Lang does a lot of chassis work that must be certified by sanctioning bodies, he's got a good handle on his weld quality.
With our new double-hump crossmember...
With our new double-hump crossmember fabricated, spray bombed, and installed, Lang can start on the Dr. Gas exhaust system. Note the ample clearance for the dual exhaust. It definitely helped that our Hooker headers were already installed.
Here are the raw materials...
Here are the raw materials we got from Dr. Gas. We used 3-inch aluminized mild-steel oval tubing, which does not have the same cross-sectional area as 3-inch round tubing, but Dr. Gas deemed it to be plenty for our 560hp, 408ci small-block. Note that the photo includes two 60-degree oval tubing bends, which were not needed. Should your project call for them (part No. OB3360) they are $57.95 each.
The first step is to hold...
The first step is to hold the cross-pipe at the centerline of the car with a pole jack. With the collector flanges loosely bolted on, cut the 60-degree transition tubes to fit. You'll need to do this in stages and sneak up on the length. The transition tubes go from 3-inch round, and transition gradually to oval, and can be slipped inside the collector flanges to help hold them in place.
As the various tubes are cut...
As the various tubes are cut to size and adjusted, you'll need to make temporary tack welds to hold them in place. These may occasionally have to be broken and reset as your geometry becomes more clear. Here, Lang uses a MIG welder to tack one of the transition pipes to the X-pipe. Again, this is an iterative process that will need to be fine-tuned.
An electric chopsaw makes...
An electric chopsaw makes easy work of cutting exhaust pipe, and yields clean, straight cuts that make for easier welding. If you don't have one, you can use a cut-off wheel or Sawzall, but you'll need to hold your work steady in a vice while cutting. Here, Lang is making a slight adjustment to the length and angle of the transition tube so that it enters the X pipe at the proper angle.
Once the length of the pipe...
Once the length of the pipe and the angle of the cut are established, and you make the final cut, it's important to properly dress the area of the butt weld. Lang likes to start with a die grinder to remove the cutting flash, then he follows that up with a Scotch-Brite pad. This burnishes the edge, removing smaller burrs, but it also helps clean the weld area of contaminants like rust and machine oil. A third step is to clean the area with acetone before welding to remove any remaining chemicals.
We've got the transition tubes...
We've got the transition tubes and the cross-pipe at the proper length and angles, and everything's been tack welded in place. Now it's time to establish the cross-pipe parallel to the floor as close as we can get it. This needs to be done before we move on to the Boom Tube mufflers. At this stage, Lang is tack welding the transition tubes to the collector flanges with some robust MIG tack welds.
The exhaust exits the cross-pipe...
The exhaust exits the cross-pipe and into the Boom Tube mufflers through a pair of oval expansion tubes. These expansion tubes don't match up perfectly with the Boom Tube mufflers or the cross-pipe, and need to be shaped with a ballpeen hammer at the corners. (They are oval in shape, and basically need to be made more "square.") This will reduce the mount of area that needs to be filled with weld media.
It's sheer folly to describe...
It's sheer folly to describe the art of TIG welding in one photo caption, but suffice it to say that it can be learned surprisingly quickly. Lang says a month or two of practicing can yield pro results if you're willing to put in the practice. Lang likens it to a combination of gas welding (you use a hand-held filler rod, not a machine-fed filler), and arc welding (where the Tungsten electrode acts very much like the stick with arc welding). The operation shown here is the collector weld, for which Lang is using 45 thousandths mild steel ER70S2 filler rod.
Note the multi-colored heat-affected...
Note the multi-colored heat-affected zone that characterizes a TIG weld, as well as the very controlled weld path. This is the mark of an experienced welder when you see this kind of precision. To finish the weld, Lang likes to use a silicon bronze filler on the outside of his exhaust welds to act as a stiffener. This imparts a "gold" sheen at the joint.
With the position of the cross-pipe...
With the position of the cross-pipe firmly established, it's time to locate the Boom Tube mufflers. The best approach is to complete one side, then mimic that placement and angle on the other side. Note that you are really working with two pieces here, the flat expansion tube that transitions between the cross-pipe and the muffler, and the Boom Tube muffler itself.
|WHERE THE MONEY WENT |
|Description: ||Source: ||Part No.: ||Cost: |
|Universal oval 3-inch cross-pipe system ||Dr. Gas ||U3O ||$399.95 |
|Boom tube mufflers (pair) ||Dr. Gas ||BTM3 ||$550.90 (pr.) |
|Universal hangars ||Dr. Gas ||339816 (need 2) ||$10.95 (ea.) |
|Mr. Gasket 3-inch header gasket ||Auto Zone ||5971 ||$8.71 |
|Total: ||$981.46 |
|PROJECT TALLADEGA THE COST SO FAR |
|Description: ||PHR Issue: ||Cost:</td> |
|'75 Chevy Laguna ||Oct. 2008 ||$5,000.00 |
|Phoenix 700-R4 trans, flexplate & converter ||Feb. 2009 ||$2,800.00 |
|Sherwin Williams paint, materials & labor ||March 2009 ||$3,979.73 |
|Makeover (tires, wheels, graphics, seats, etc.) ||April 2009 ||$2,989.95 |
|408ci solid-roller small-block ||May 2009 ||$7,685.00 |
|Global West rear suspension ||June 2009 ||$1,699.36 |
|Global West front suspension ||July 2009 ||$2,569.83 |
|Global West front brake upgrade ||Sept. 2009 ||$1,118.45 |
|Engine and trans installation ||Oct. 2009 ||$3,430.36 |
|Dr. Gas side-exit NASCAR exhaust ||Nov. 2009 ||$981.46 |
|Total: ||$32,254.14 |
The Dr. Gas Boom Tube mufflers...
The Dr. Gas Boom Tube mufflers come squared off, and you'll need to make a decision where you want to cut them, and at what angle. Here it helps to have one or two extra pairs of eyes to check the appearance from a distance. The two major factors we considered were achieving the right angle (parallel to the body), and keeping the end close enough to the car to look cool while not allowing fumes to get inside the cabin.
Now the fun part! Cutting...
Now the fun part! Cutting the Boom Tube muffler to your chosen length and angle. Have your work secured solidly, wear eyewear, and take your time. Cut it crooked and you'll have to live with the looks for a long time-or start over. At the edge of the photo, you can see one of the spin traps that are welded in the interior of the muffler. These are the only thing attenuating the noise of this otherwise open exhaust system.
This shot of the oval expansion...
This shot of the oval expansion tube (after being welded to the muffler) shows a couple of things. The angle of the transition may not always be straight out of the cross-pipe, and here it's being trimmed on one side with the cut-off wheel. You can also see how all that work hammering the oval transition into a more square shape has paid off with a stronger, better-looking TIG weld.
Coming in the home stretch,...
Coming in the home stretch, the Boom Tubes and expansion transition pipes have been welded to each other. Also, the Boom Tube and transition on the driver side has been duplicated (length and angle) to match the passenger side, which was done first. At this point, Lang is making some MIG tack welds to establish the final position. This will allow you to do a walk around to check the height, length, and angle of everything. Some tweaking can still be done at this point, and tack welds can be broken if things aren't perfect.
At this same stage, we searched...
At this same stage, we searched for, and found, some convenient pre-existing holes in the frame where we could mount the exhaust hangers. This should be done only after you have established the position and angle of the Boom Tubes.
Once we were happy with where...
Once we were happy with where everything lined up and the tack welds were completed, we removed the mocked-up exhaust, and Lang completed the remaining TIG welds on the bench. By now, the entire system was becoming pretty unwieldy. On the positive side, it's now a solid unit, that can be easily removed and reinstalled should the need arise.
The finished exhaust system...
The finished exhaust system before being installed on Project Talladega. It looked like a work of art that would be suitable for hanging on the wall. Shortly after this, we tagged the whole system with a can of high-temp aluminum exhaust paint we had lying around, then bolted it to the car for good.
ON THE WEB Want to know more...
ON THE WEB
Want to know more about TIG welding? We have a lot more information about TIG from Lang Paciulli of LP Racing than could fit here, so we've placed that on the web as an exclusive. If you think you want to get your hands dirty with a job like this, log on to www.popularhotrodding.com, keyword search "TIG Welding."