1971 Buick Skylark - Chassis Dyno Testing

'While you might consider buying testing time on a vehicle chassis dyno an expensive luxury, we hope you'll at least read this article to consider the possibilities. If anything, what we experienced in creating this story wasn't what we expected, but the safety, durability, and performance unleashed would have definitely been more painful to discover and resolve without time on the chassis rolls. To learn the most we could possibly learn, we partnered with the pros at Wheel to Wheel Powertrain (W2W), in Madison Heights, Michigan, as we ran a vehicle through its paces on the company's four-wheel-drive Mustang chassis dyno.

The Setup
So we dug up a pretty common vehicle for Car Craft: a barely streetable, cool-to-look-at-and-see-driving, somewhat-fast-at-the-dragstrip and seemingly ready to go faster with a little tuning street/strip machine. This '71 Buick Skylark GS Stage 1 killer is replete with a Dyer's 6-71 wheezer adding to the street cred of this 468ci all-Buford ride. Owner Mike Kunkle bought the car mostly complete about a decade ago and has been tuning on it ever since with the idea of getting into the 10-second club in the quarter-mile.

He has always felt the engine made enough power to go 10s but has never had the engine or vehicle on a dyno. Previous runs at the dragstrip have resulted in tire-smoking elapsed times in the 12s, with trap speeds in the 108-mph range, and after the dyno tune, the car went 11.55 at 114 mph.

The issues this car was faced with were not unusual on the street, making it a good starting point for going to the chassis dyno. The goal was to find out if there were any simple fixes/upgrades that would result in "found" power and improve the chances of a more impressive e.t. Some unexpected finds helped minimize the chances of burning the car to the ground and inadvertently breaking parts, so we'll add that in hindsight-and you should, too-when you test at the chassis dyno.

The Experience
If you haven't seen a chassis dyno in action, here's the deal. There is a lot of setup time, the actual testing is brief but exciting, and the resulting power numbers are usually numbing-but not in a good way. Invariably, enthusiasts think their vehicles make much more power at the wheels than they really do. In fact, as far as we're concerned, there should be a special private room in which to share the power numbers for the first time-as this is usually gut-wrenching.

The testing with this Buick wasn't unusual in any of those respects. W2W dyno operator Rich Gala drove the vehicle onto the chassis dyno and positioned it so the rear wheels were over one set of the dyno rollers (this is a four-wheel-drive dyno, so in this case, only one set of rollers was used). Large straps were used to lock the vehicle down onto these rollers, and powerful fans directed at the radiator and under the vehicle kept everything cool during the runs.

The modern chassis dyno cell, like this Wheel to Wheel Powertrain (W2W) four-wheel-drive Mustang dyno cell, is designed to provide repeatable testing for every type of vehicle up to big horsepower race cars.
The modern chassis dyno cell, like this Wheel to Wheel Powertrain (W2W) four-wheel-drive M
Since vehicles spew serious amounts of exhaust during the wide-open-throttle (WOT) testing, W2W uses an evacuation exhaust system that consists of large fans sucking air through these oversized metal hoses and out through the roof.
Since vehicles spew serious amounts of exhaust during the wide-open-throttle (WOT) testing

The process of mounting a vehicle onto a chassis dyno differs based on whether the dyno is installed in the floor or above ground (as the W2W dyno is). On an above-ground dyno, the vehicle is pulled onto a lift, as it being performed here, and raised up to the dyno floor.
The process of mounting a vehicle onto a chassis dyno differs based on whether the dyno is
The Buick was backed onto the dyno until the powered tires were on the rolls-the power-absorbing steel drums the tires ride on. This vehicle only has the rear wheels powered, so the front rolls were not used. A four-wheel-drive vehicle would have all its tires on rolls and is much more difficult to strap down, as it actually floats on the rolls during the testing.
The Buick was backed onto the dyno until the powered tires were on the rolls-the power-abs

The W2W dyno can record air/fuel ratio O2 sensor data during a run, but this vehicle did not have an O2 sensor bung in the headers. To assist in the tuning, Denny Dera from the W2W fab shop installed a bung in the passenger header. This would prove to be valuable later on.

The Findings
Check out the photos and sidebars to see how the testing went and what you can learn from our pain. Without a doubt, the chassis dyno testing discoveries were more than just horsepower-the car is much safer and consistent. Now, the car should be able to make some laps at the dragstrip with the focus being on getting the car to hook at the line and using all the power it is making.

Kunkle is planning a new engine to produce the 600 rear-wheel horsepower W2W says he'll need to run in the 10s. He's a believer in chassis dynos and looks forward to coming back to the dyno rolls with his new engine installed to debug it before heading out to the dragstrip.

Dyno Testing Results
The chassis dyno is a brutally honest piece of equipment, but it tells you much more than just power output. If a vehicle is unsafe or unreliable, the dyno will expose it. We ran into multiple issues that needed to be resolved, and the vehicle is better for having corrected them. They are listed along with the power improvements because of their value to the overall performance of the vehicle.

TEST STEP	RESULTS	DIFFERENCE
Performed baseline testing	320 hp	n/a
Checked throttle travel at WOT	320 hp	0 hp, but peace of mind
Checked timing	326 hp	+6 hp, set to 35 BTDC
Tuned carb setup	326 hp	0 hp, but smoother idle
Fixed vacuum/pressure leaks	350 hp	+25 hp, blown-out gasket
Fixed underhood oil leak	350 hp	0 hp, minimized fire hazard
Fixed leaking transmission pan	350 hp	0 hp, durability improvement
Fixed slipping blower-belt tensioner	350 hp	0 hp, improved reliability
Repaired blown transmission	370 hp	+20 hp, replaced torque converter
Increased boost with Dyer's pulleys	390 hp	+20 hp, 1.5 pounds of boost
Horsepower results from testing	390 hp	+70 hp

W2W chassis dyno operator Rich Gala is skilled at strapping vehicles to the dyno. The positioning of the tie-down straps and the tension on them is critical to keep the vehicle in place during the testing. Various recording connections are also hooked up at this point, like engine rpm, manifold vacuum/boost, O2 exhaust gas, and others that the dyno records along with power output for future reference in problem and power research.
W2W chassis dyno operator Rich Gala is skilled at strapping vehicles to the dyno. The posi
Since vehicles are designed to shed heat via the air rushing through the radiator and under the vehicle, a chassis dyno needs to have a dramatic amount of air pushed through the radiator and under the vehicle. The W2W dyno uses a series of these high-volume and high-pressure squirrel fans and has a large fan pulling air throughout the entire dyno cell.
Since vehicles are designed to shed heat via the air rushing through the radiator and unde

As Gala put it, "I always make a baseline run without looking at anything as long as the timing is safe, then immediately check that the throttle blades are opening 100 percent. I've had some great finds. On a recent 450hp vehicle test, we gained 30 hp by getting the throttle fully open. I usually find single-digit horsepower with this one check." In this case, Kunkle had addressed the issue the previous year, and the throttle blades were opening 100 percent.
As Gala put it, "I always make a baseline run without looking at anything as long as the t

OK, so this is the brutal part. Just about every enthusiast believes his vehicle makes more power than it really does. Before going to the dyno, prepare yourself for the reality and try to focus on just making solid improvements in power, reliability, and durability.
OK, so this is the brutal part. Just about every enthusiast believes his vehicle makes mor
With the vehicle strapped down, Gala "drives" it on the dyno to get everything up to temperature and then makes a few baseline runs to generate initial horsepower and torque results.
With the vehicle strapped down, Gala "drives" it on the dyno to get everything up to tempe
Gala used a timing light to determine both the initial and final ignition timing. The Buick had 32 degrees of timing advance in it, which seemed conservative. So a few runs were made with 3 degrees more timing advance in them, which resulted in what appeared to be a 6hp gain.
Gala used a timing light to determine both the initial and final ignition timing. The Buic

They found a blown-out intake gasket was so gone (see gasket closeup), it's hard to believe the engine ran at all. Kunkle also found a wide spray of fuel and oil on the firewall. A new gasket was installed and the blower case was torqued down onto the one-off intake manifold.
They found a blown-out intake gasket was so gone (see gasket closeup), it's hard to believ
The W2W team (now including General Manager Kurt Urban) thought there was a problem with the carburetors because the engine was cycling on idle speed. But on further investigation, a serious vacuum leak was discovered between the blower and intake manifold. The vehicle was removed from the chassis dyno to be tested again another day.
The W2W team (now including General Manager Kurt Urban) thought there was a problem with t

During one of the later power runs, when the engine was making good power and Gala was legging it up the rpm band, the engine bay gave off a large flash of fire and a plume of smoke. Gala immediately shut down the car and looked under the hood. After some time inspecting the vehicle, he discovered the dipstick tube was not installed securely, which dumped hot oil out of the engine oil pan onto the headers at high rpm. Ace W2W machinist Bill Blair whittled up a stainless tube that press-fit into the block and held the dipstick at the proper height. Problem solved with a minimum of damage and fright.
During one of the later power runs, when the engine was making good power and Gala was leg
As the testing progressed, the W2W team kept noticing the boost for the engine was only in the 9-psi range at peak rpm. They felt the engine should be seeing at least 10 psi or more, so they ordered a set of slightly overdriven pulleys from Dyer's Blowers in Summit, Illinois. The crank pulley needed to be redrilled to fit this application, but otherwise, the pulleys bolted on and netted a little boost in overall power. The final analysis was that the 6-71 blower either needed to be spun much harder or an 8-71 blower needed to be called in to service the big-block Buick to more horsepower. But that will be a project for another day. We learned a lot, the car is much more consistent, and it made a little more horsepower along the way.
As the testing progressed, the W2W team kept noticing the boost for the engine was only in
After each major discovery, which included the intake-gasket leak, blown transmission, and leaking dipstick, the vehicle was removed from the chassis dyno, repaired, and brought back. Was this frustrating? Are you kidding? Yes, it sucked, but it was more educational than going to the dragstrip-and everyone is confident the car would've burned to the ground without this dyno day.
After each major discovery, which included the intake-gasket leak, blown transmission, and