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August 22, 1997
Holley SysteMax II Performance Package In Action
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It's been longer than we expected, but we've finally gotten the chance to test Holley's SysteMax performance package for 5.0 Mustangs.
A quick recap to bring you up to speed. Holley is almost ready to release a new performance package for 5.0 Mustangs, they call it SysteMax. The package is extremely complete and comes with a set of aluminum cylinder heads, upper and lower intake, cam, head-bolts, timing chain, pushrods and a few miscellaneous gaskets. Holley gave us this kit and asked us to install it on a car and let them know how it worked.
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First Impressions
As you would expect, everything from Holley is very high quality. And it's a very complete kit.
 The cylinder heads are nice pieces. They're nothing exotic or innovative, but they are quality pieces. The exhaust port has a very nice short turn radius. The deck is extremely thick and should hold up well to boost/nitrous. All the valve train hardware is top notch and the assembly is excellent. The chambers are 62.5cc. The heads come with a light CNC bowl job and intake port match. All-in-all a high quality head that has the potential to do well and make a fair amount of power on a street/strip car.
The Holley Exhaust Port
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Holley's Intake Port
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The flow numbers for the heads out of the box are as follows:
Holley Cylinder Head Flowbench Results
| Lift |
Intake CFM @ 28" |
Exhaust CFM @ 28" |
| .100 |
63.5 |
56.1 |
| .200 |
124.0 |
100.4 |
| .300 |
173.7 |
129.6 |
| .400 |
206.2 |
155.1 |
| .500 |
221.1 |
167.2 |
| .550 |
228.0 |
173.2 |
| .600 |
232.8 |
175.7 |
Flow Numbers are "As Cast" - No Porting or Clean up
 The real news is the intake. The ports are extremely generous and should easily outflow a ported GT-40. Holley started with the truck intake design and made some major improvements, especially the size of the runners. The upper looks very similar to the Vortech/Saleen intake but fixes some of their design flaws, and like the lower has very generous runners. We expect big things from this intake. Holley hasn't set pricing yet and we're not sure it'll be as economical as the Cobra intake, but it definitely has the potential to make more power than any of the other full runnered intakes on the market. |
Holley's lower intake (top) has significantly larger runners than a GT-40 (bottom). This additional runner volume is perfectly suited to forced induction engines and especially stroked 302's.
Hopefully we'll soon see a 351W version.
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The cam that comes with the kit is an inverted roller, an extremely nice design that is more expensive to machine than traditional hydraulic rollers but generally makes more power than one with similar lift and duration numbers. Most of this is achieved by the accelerated ramp speeds of an inverted roller. However, at first glance we felt the cam had too much duration for the average street car.
The cam specs are as follows:
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I Duration @.050
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E Duration @.050
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Intake Lift w/ 1.6
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Exhaust Lift w/ 1.6
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Lobe Sep
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221°
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223°
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.509
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.508
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107°
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The Test Car
The car we decided to install the SysteMax on was a very clean, low mileage, AOD, 88 LX coupe. The coupe is fully loaded including air conditioning and weighs in at 3450 with driver. So it was far from being a light-weight.
The car already had a few modifications done to it; Motorsport Shorty Headers, 2 1/4" off-road pipe with 3 chamber Flowmaster mufflers, a 4.30 gear (which believe it or not isn't too much for a stock AOD car) and a Performance Industries 2000 rpm Stallion converter.
The first thing we needed to do was establish a baseline ET before the installation of Holley's SysteMax package. Our baseline was established at Ubly dragway, about 2 hours North of Detroit. It was a typical humid Michigan Summer day with temps in the low to mid 80°'s. All runs would be made with a set of 26 x 10 Mickey Thompson ET Drag Slicks for optimal traction. For a mostly stock Speed Density car, it ran very well. It's best run was a 13.80 @ 96.31 and a 60 ft. time of 1.83. All other runs were very close, and we left the track with what we feel is a very consistent baseline.
The Installation
So it was back to the shop to install the SysteMax package on our willing recipient.
The installation went very smoothly for the most part with only a few hitches. As we said, the upper intake resembles the Saleen/Vortech intake, and the Saleen/Vortech intake is notoriously difficult to install. Holley's fixes some of the installation obstacles and was easier to install than the Saleen/Vortech, but it is still much more time consuming than installing the straight-forward GT-40 or Cobra intakes.
Another obstacle we ran into involved the valve covers. Holley revised the valve cover rail, it appears to be lower than stock. This caused a clearance problem with the 1.7 Cobra rockers that were installed with the package. The only valve cover that we could get to fit properly are the 92 - Newer valve covers which have no internal ribbing. But for the most part, everything fit well and looked nice.
Knowing the cam is on the big side, we decided to install it 6° advanced to move the power band down a bit and increase low end torque.
We had to perform some additional modifications to the car to make the package work. Since this LX was a SD car we had to convert it to Mass Air. It got the usual Motorsport Conversion Kit and we used a Pro-M 77mm Mass Air Meter. The car was also treated to a 65mm throttle body and knowing that the car will soon have a Vortech Supercharger, 36 lb/hr injectors.
One note on the injectors. Some people may feel that they are overkill in the current combination. While we'll admit he could have gotten by with 24 or 30 lb/hr injectors, the car liked the larger injector. We even had to raise fuel pressure to 50 psi (over the factory 38 - 42 w/o vacuum) for the engine to make power in the upper rpm's. So in this case, the large injectors weren't hampering performance, they were helping.
Initial timing was set at 18°.
The Test Drive
Like any other installation we perform, the car is routinely treated to a test drive to ensure driveability and everything else is perfect. It was immediately evident that the car lost some low end torque. The 2000 rpm Stallion converter was suddenly inadequate. We knew the car would not be able to perform well with the converter being so tight so we installed a 2800 rpm Stallion. It felt better down low, but still kind of soft, we had hoped for more low end.
Back to the Track
We were confident that the car was running well, so the car's owner (who is an experienced drag racer) took the car back to Ubly Dragway to see how much of a difference the package made.
The weather was very close to when the car was baselined. Low to mid 80's and on the humid side. The car was again run with MT 26 x 10 ET Drags. A total of 8 passes were made with approximately a 1/2 hour cool down between each pass. Of all 8 passes the ET varied less than a tenth, the car was running very consistent, it's too bad Toni (the car's owner) wasn't bracket racing. The car's best pass of the day was 13.21 @ 106.68 with a 2.04 60 ft. time. Not quite the gain we had hoped for.
According to the weight vs. 1/4 mile mph method, our car made 245 hp before the SysteMax installation and 334 with the package. That's a gain of 89 hp. Not too bad, although we had hoped for a solid 100 hp gain, but the ET was still not showing that great an improvement.
We feel that with a few more degrees of timing there may be a tenth or even two left in the car. The owner didn't experiment and we weren't at the track to suggest it. But the major problem is that the cam is really too big for the average Mustang. To optimize the current combination we'd need a 3600 - 4000 rpm stall converter, and that's kind of excessive for a daily driven Mustang. And that's with the cam advanced 6°! If we had installed the cam straight up it would need even more stall speed. A smaller cam with less intake and exhaust duration would go a long way to increase the ET. With the SysteMax package installed, the car's 60 ft. time actually worsened, and traction wasn't the culprit, the car wasn't spinning any tire. The problem is the lack of low speed torque that Holley's cam is responsible for.
The Bottom Line
Overall, it's a nice package and Holley claims that it'll be very affordable - under $2000 for the whole kit. As we said the heads are nice, but they're nothing exotic and TFS Twisted Wedge heads certainly produce more power. The intake we like a lot. It has great potential for more serious 302's but the full extent of its capabilities won't be realized by the average car. But the cam is just too large for mild applications like this one. It reduces the package's overall potential by killing low speed torque, which is very important for a street car.
We'll update this story as soon as the car returns to the track with a little more timing and a looser converter, check back in two or three weeks.
UPDATE: We installed a Precision Industries converter that stalled to 3200 rpm and the results were encouraging. With no other changes, the car picked up almost a full 3 tenths, posting a new best ET of 12.92. The bad news is that it also lost almost 3 mph because of the looser converter. But we're heading in the right direction. With an even looser converter the car may be capable of 12.70's. But since this car will have a Vortech Supercharger in the Spring we're going to leave things just as they are. A looser converter would be fine for if the car would stay NA, but it'll be far too loose with the extra torque from the boost. All in all Holley's package provides an impressive gain and would be even better for the average street Mustang with a smaller cam.
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