Making a car run the best it can has different meanings for different people. Some feel that however a car runs just by assembling the parts is good enough. Then, there are the few that really make a science out of perfecting how a car runs. Not only is proper parts selection paramount, but every part is then scrutinized to make its small part of the complete package as best as it can be. Then, you have the guys that race their Mopars in the Pure Stock Drags.
This class of racing puts a unique twist on the 1320 because the rulebook requires cars to be very near stock—stock engine components like the block, heads, intake, and carburetor are a must. What's more, the cam must retain an original equipment grind and the valvetrain must be stock. It's so restrictive, that porting of the heads, or even port matching are not allowed. To make power, an engine must breathe, but these cars even have to run factory cast-iron exhaust manifolds, mufflers, and tailpipes—all in the factory location.
Normally, a slick or at least a larger tire can help you when you launch, but not for these guys. They have to run factory-sized tires. In this class, you can't just throw horsepower at the car to go fast. You've got to build the right power for the available traction, position it correctly in the power band, tweak the engine for the car's rear gear, harness it deftly, and ride that moving the line between traction and wheel spin. If you do it right, you'll be on your way to a hot e.t. If not, your opponent runs off and leaves you—and there's no way to recover lost time. Even though the Pure Stock racing rule book has survived with few changes over the years, the cars seem to get faster and faster each year thanks to more meticulous engine machining, chassis prep, and driving practice.
Recently, we spent some time at the Pure Stock Drags that are held at a remote track in the middle of northern Michigan's potato fields. We wanted to see just how the Mopar guys were running, and see if we could get a glimpse into what it takes to make these boe stock cruisers run like race cars.
|Top 10 Mopars At the 2012 Pure Stock Drags by e.t
|| Mike Leyes
|'69 Road Runner
|440 Six Barrel
|'64 Plymouth Sport Fury
|426 Max Wedge
|'67 Plymouth GTX
|'69 Road Runner
|440 Six Barrel
|440 Six Pack
|'70 Challenger R/T
|440 Six Pack
|'67 Dodge Coronet R/T
|'64 Plymouth Belvedere
|426 Max Wedge
|'68 Road Runner
Blue Bell, PA
1968 Plymouth Road Runner
Engine: 426 Hemi
11.54 at 125.31
Making the biggest headlines of the meet was Rick Mahoney's Dark Midnight Blue '68 Hemi Road Runner, an original Hemi/four-speed car. After a fresh build by Scott Tiemann's Supercar Specialties, it debuted this spring with a four-speed and Dana 60 rear, running a best of 11.73 at 125. But, at this event, and for consistency, the four-speed was temporarily exchanged for a TorqueFlite.
The Road Runner was an all-out effort, with a Ray Barton Hemi under the hood, built to blow away anything that's ever run at the Pure Stock Drags. It's a state-of-the-art powerhouse, having clocked a blazing 10.92 at 126.93 on a 1.71-second short time at Maryland International Raceway last October with Rick at the wheel.
At the Pure Stocks however, the Friday spin-fest netted a best e.t. of 11.82, making him the number six qualifier. That night, a couple of changes were made to boost traction and dial back the Hemi a little.
Ignition is standard Chrysler electronic, but they bring several distributors that have varying advance curves, and at this event, they swapped for the slowest curve. It still gets full advance, but not until 4,500 rpm.
They also added 175 pounds of weight to the trunk.
"Right off the trailer on Saturday, Rick ran 11.54," Scott told us.
In the afternoon shootouts, Rick drew Larry Kirkum's aluminum-headed, Tri-Carbed 427 Corvette. In Round One, he backed up the 11.54, running just a blink away from an 11.49 (11.49 and quicker must have a rollcage or be DQ'd for this year and next). But it was Round Two when it all came together.
"I could tell as soon as I stepped on the gas that this was our best run of the weekend," Scott said. "It hooked up perfectly and shifted clean. I slammed on brakes at about 1,000 feet...that would have been low 11.30 or high 11.20," Scott reports.
"What's amazing is that the car weighed 4,025 pounds—I had 175 pounds in trunk when it did that."
Calculate in that their best 60-footer was a modest 1.95, and you can see the Road Runner's blockbuster performance. That's quicker than much of the heavily modified F.A.S.T. racers.
Scott is adamant that the car is rules-compliant, and he's forthcoming about most of its details, but a few things are classified, at least for now.
The block is .030-inch over, with a Chrysler forged crankshaft, offset for .013-inch more stroke, which is less than the legal maximum of .015-inch. Displacement works out to be 433.34 cubic inches. It's built with Diamond pistons and aftermarket steel rods in the standard Hemi length.
"No one thing makes it great," says Scott, "but a lot of little things make it great."
For example, after observing the oil pressure gauge behaving badly during dyno runs, the oil's return path to the pan was changed. with help from a fellow racer, tubing now diverts the oil to the sides instead of it draining onto the spinning crankshaft. That prevents the oil from foaming, stabilizes oil pressure, and removes an obstacle from the crank's free rotation.
Scott and Dave also specified a cam with wider lobe centers, believing that Barton's Hemi may work better on the dyno, but a slightly more modest grind (.480/.475-inch intake/exhaust at valve) would be better suited to the OEM exhaust manifolds and closed exhaust that Pure Stock cars run. A smaller cam seems counter-intuitive, but a stocker is a different animal, and normal rules of race-engine building don't necessarily apply.
Rules cap the exhaust pipe size at 21⁄2 inches, but cross over pipes are allowed. The Road Runner uses mandrel-bent tubing, the same stuff that everybody runs, and the mufflers are Walker long ovals.
The recipe worked, as the engine dyno'd at over 700 horsepower at 6,900 rpm.
Besides the signature glow of a Scott Tiemann restoration, Mahoney's Road Runner has a unique sound as it screams down the track heading for the traps at a howling redline.
1970 Plymouth Baracuda
Engine: 426 Hemi
11.94 at 118.68
Bob Karakashian is a well-known Mopar racer and former IHRA record holder. Ask any Mopar guy, and they'll say that he deserves some kind of lifetime achievement award as a front-of-the-pack fixture. The Cuda has run a best of 11.59 at 121.25 at Milan, and at this meet, he qualified 9th using old reproduction Polyglas GTs.
Bob says that there's no real trick to making power with the Hemi.
"The Hemi makes the power by blueprinting," he maintains. And his 'Cuda engine is pretty conservative. The block is .060-inch over, the crankshaft is a standard factory-forged unit, and still uses a factory balancer. The connecting rods are stock-style forged Manley I-beams, and CP pistons with the stock ring package finish it off. There's nothing trick, just very careful attention to machining to ensure cylinder sealing and minimal friction.
One thing that Bob insists on is his proprietary "Mr. Six Pack" camshaft. "My camshafts look small on paper, but have a much faster rate of lift," explains Bob. "Mr. Six Pack camshafts are very close to stock lift, and are single pattern just like the factory. They use the fast ramp that Mopar used back then. They're not Chevy lobes like most cams use today."
The balance of the valvetrain is all stock—rockers, shafts, and a single valve spring that the factory had on the '70 Hemi. Like we said, no porting or even port matching is allowed.
Bob hasn't dyno'd this engine, but he did dyno one virtually identical, which made 565 hp at 6,700 rpm.
Bob's 'Cuda is a column-shifted automatic, and he rebuilt his own TorqueFlite which, like the engine, is essentially stock—no rollers, no aluminum, all factory parts.
"The torque converter is an 11-inch Turbo Action that's been in the car for about 20 years. Stall speed is about 1,800 rpm—I'd like it to be about 2,000 or even 2,100."
The axle is an 83⁄4 with digger 4.30:1 gears.
The 'Cuda makes good if not spectacular power, but driving it is a big part of its success. The Hemi can easily overpower the tires, even on a sprayed starting line, so Bob brings it out just above idle, then gets into it once the wheels are rolling, and 60-foots in the low 1.80s.
"With an E-Body, it's a little bigger challenge to get the car to launch because there's no [rear] overhang," says Bob, who is accomplished as both an E- and B-Body pilot. "When the second carburetor kicks in, it's really violent. The back of the car is so light, [and] that's part of the problem. Unlike other racing classes, the faster Pure Stock racers usually have to add weight to increase traction and go faster. With Bob aboard, his 'Cuda weighs 3,765 pounds.
If you can exercise throttle restraint in the early going and not give the race away in wheel spin, the Hemi will rally to win a lot of races.
"The 440 Six Pack has the torque off the line, but the Hemi has a top end charge that out powers it. The Six-Pack, up to 800 or 1,000 feet will run with a Hemi all day long, but [after that], the Hemi takes over like gangbuster."
Last year Bob ran 11.62 at 121 at the Pure Stocks. He was off over three tenths this year and thinks he knows why.
"I had different fuel with a pinch more octane and I think it actually slowed the car down."
1970 Plymouth Duster 340
13.37 at 102.75
Tom Cannon is a Mopar guy from way back. He runs an orange '70 T/A Challenger and a red and white '71 Super Bee in the F.A.S.T. races. For Tom, the Pure Stock Drags, competitive as they may be, is a chance to kick back and relax.
When we told him that he had the quickest Mopar small-block at the Pure Stock Drags, he was surprised. "I don't know what to tell you," he said humbly.
The numbers-matching block was removed and set aside, and a replacement '71 block was blueprinted along NHRA guidelines and installed with the '70 heads, intake, and carburetor. The '71 block is identical to the '70, but there are differences elsewhere.
"The 1970 engine has the Carter AVS carb, and the '71 has the ThermoQuad," Tom points out. "The difference is that the AVS is 625 cfm and the Thermoquad is 800." That's a sizeable difference in ratings, but it may not translate into more power because of changes elsewhere.
"The '71 340 has a different passenger-side exhaust manifold," Tom explains. "It has a smaller, more restrictive 17⁄8-inch outlet. The 1968-1970 manifolds had a 21⁄4-inch outlet." So the bigger carburetor and smaller exhaust manifold probably offset each other. Swapping the carburetors for testing is on Tom's to-do list, but he hasn't done it yet.
Tom says that the rest of the engine is very near stock. "I run the factory Prestolite dual-point distributor. I've never tried anything else." He sets it up on a vintage Sun distributor dyno, with Accel high-performance points (they have a stiffer return spring to prevent bounce), and 35 degrees of advance that are all in by 1,200 rpm. Unlike the high-powered Hemis and 440s, that reduce timing to preserve traction by slightly curbing engine output off the line, the 340 is not riding the ragged edge of traction, so he brings in full advance very early.
The air filter is a run-of-the-mill paper unit, and the Carter AVS has the stock jetting, which Tom says delivers the optimum air/fuel ratio, or very near it.
340 Dusters also have an issue where the driver's side exhaust pipe snakes through the engine compartment. The pipe has to be crimped for clearance at the starter, Torque shaft, Pitman arm, and torsion bar.
"It's squeezed down to 17⁄8 inches for around 3 inches," says Tom, who adds that there's just no way around it, even with a custom pipe, which he runs.
The balance of his exhaust is 21⁄2-inch duals, with no balance tube, and a pair of Walker Dynomax Super Turbo mufflers.
If you're expecting to find hidden tricks under the hood, they're just not there. "E.T. is all about the starting line," says Tom, and to that end, he runs a four-speed with 4.30:1 gears in the Sure Grip differential. Driving technique is also simple. "I just hold 1,500 rpm, ease the clutch out, and when it's fully engaged, I mash the gas."
That simple, basic launch gets the Duster off the line with low 1.90 short times. From there, Tom makes the 1-2 shift easy, a little harder for 2-3, and leaves his foot on the floor for 3-4.
The 3.91 gears put it across the line at the top of 3rd gear, while the 4.30s go through the traps at the top of 4th. The suspension is stock, and while the high-powered cars launch better on over-inflated rear tires, Tom's experiments with tire pressure proved one thing. "I've tried from 23 to 42 psi, and the Duster just doesn't care."
Tom makes his runs with half a tank of 110-octane racing fuel in the tank. The high-powered cars on the edge of traction like to run a full tank, and even add weight to the trunk as the improved traction more than offsets the penalty of weight.
All time low ET for the Duster is 13.20. That's over a tenth quicker than its very consistent 13.30s, thanks Tom suspects, to a water burnout there, which was not available at the Pure Stock Drags. Its lower elevation (320 feet at Cecil County vs. 919 feet for the Mid-Michigan Motorplex) may have also been a factor.
It sounds like the biggest difference between the big-cube B- and E-Bodies is that while they have to take steps up to and including reducing engine output for their limited traction, with the small-block, you can pretty much let 'er rip.
"It could go faster," Tom says. "There's a smidge of compression left on the table. It's got a little less than 11.5:1 and rules allow up to 12.0:1. Also, if it had an automatic, it would probably go in the 12s. Looking at the race results, there are cars in the 12s or close running my trap speed."
"Stepping out of those 11-second cars into the low-13s Duster is like watching paint dry," Tom quips. Yeah, maybe a quick dry.