Here, SLP's ace Tony Kalpach is seen removing one of the two motor mount brackets for acce
As with most header installations, the spark plugs and oil dipstick tube are a few of the
SLP's stainless steel ceramic-coated (inside and outside) 1-5/8-inch front header offers l
Here, you can see the size difference in the flange area where the exhaust enters the head
After baselining our GT once again, we moved to the installation room to install the SLP headers. It took roughly 611/42 hours for SLP's Tony Kalpach and myself to hang them. Unfortunately, our GP came equipped with the California air pump package, requiring the air tube and flange to be welded to the rear header (thanks, Ken Estelle). Our 3800 happened to be only the second application in many installations that SLP has seen with the smog pump. As most 3800s don't have the smog pump, hard-core gearheads with decent hand tools, a floor jack, and jackstands should be able to bolt-up SLP's headers in about a day's time.
Once strapped down to the dyno with the new headers, front pipe, and high-flow cat in place, the SLP guys informed us this was the first nonsupercharged V-6 to test their tubes. Director of Engineering Brian Reese mentioned they have seen as much as a 29hp increase on blown applications. After spinning the rollers, we were pleased to learn we picked up 20 hp on our natural six. SLP's headers clearly kicked butt! No doubt, the previous intake and exhaust mods from Part I contributed to the header's performance.
In search of a few more horses, we attended to the cooling system. The 3800 retards the timing a few degrees when the coolant rises over 195 degrees. On all our previous dyno pulls, the coolant temp was between 201 and 212 degrees. We backed off the dyno and headed back to the installation room to drain the coolant to install the SLP 180-degree thermostat (PN 100180, $17.95). The radiator was filled with straight distilled water and a bottle of Redline WaterWetter (it was August and over 90 degrees outside). Next, SLP's fan-control switch (PN 63013, $69.95) was installed. The switch features three positions-manual low, high speed, and stock.
We positioned the fan switch on manual low for the GP's return to the rollers. On back-to-back dyno pulls, the coolant temp ranged from 180 to 190 degrees. As you can see, the coolant change, the 180-degree thermostat, and the fan switch lowered the temperature an average of 21 degrees. SLP's SuperFlow dyno computer showed us the knock retard sensor didn't retard the timing, and we were rewarded with 2 extra horsepower for our efforts.
With the newfound power, we were anticipating gas mileage gains. Happily, after many mileage checks, we noted another mile to the gallon. The added mileage was recorded on the same 180-mile round trip (70 mph, A/C on with three passengers). Here's the breakdown of the recorded highway mileage statistics-stock, 25.4; Part I, 28.2; and Part II, 29.1 mpg. Around town also showed increased mileage, stock was 17-19 mpg; now we're seeing 20-22 mpg.
- After all that dyno testing, we wanted to see how quickly the thrifty six could go down the quarter-mile. But getting the car from my busy wife is tough-the GP is our only car.
We have witnessed many bone-stock 3800 GP GT's running mid to low 16s-we're expecting to go a second faster. Tune in next time as we take the Pontiac from my wife and go strip test it!
Test Notes: Air inlet temp at the airbox in the dyno room averaged 108 degrees F for all tests Baseline conditions: 86 degrees, 52 percent humidity, 29.91 barometer Part I after-mods conditions: 90 degrees, 49 percent humidity, 29.85 barometer Coolant temp was 201-212 degrees F during baseline and Part I after mods testing Part II after-mods conditions: 91 degrees, 58 percent humidity, 29.81 barometer Coolant temp was 180-190 degrees F during Part II after-mods testing