As a refresher, we started out with a bone-stock '87 Buick GN, base-lined it, then progressively dyno and strip tested a host of proven bolt-ons. Each time we tried a new upgrade, we visited our friends at Tune Time Performance for dyno testing to see the power gains and to be sure of a safe air/fuel ratio-we didn't want to hurt our buddy Tim Cairone's Turbo Buick. By taking advantage of today's technology and 20-something years of R & D going into the TB motor, we were able to safely add over 100 rwhp, 200 lb-ft torque and lower e.t.'s by 2 seconds without changing any of the engine's internals. That was risky business and a lot of power to be gained from a motor with over 100,000 miles. This led us to freshen-up the bottom end of the original (numbers matching) 3.8-liter V-6 for the swap to the roller cam and ported heads.
Back in Part 4 we installed and tested PerformaBuilt Transmissions' rebuild of the GN's original 200-4R along with its 10-inch billet 2,800-stall converter. The PB transmission and billet 10-inch converter lowered the 60-foots from an average of 2.2 to 1.65. Quarter-mile e.t.'s dropped big time from mid 13s to low 12s. Feeling confident after testing PB's beefy trans/converter with
its two-year unconditional warranty, we were ready to shoot for the 11s.
In order to run 11s without lots of boost (over 20 psi), we knew we needed to ditch the outdated stock flat-tappet cam for a more recent technology hydraulic roller-tappet stick from Comp Cams. Teamed-up with the roller stick was a set of well-ported stock iron heads by Jose Motor Sports to increase airflow through the forced-air fed Buick V-6. We planned on a budget rebuild and reused the stock cast pistons and rods instead of using a lighter and stronger rotating assembly as not to skew our test results of the swap to the roller cam and ported heads.
For this episode we'll drop in the refreshed short-block with the roller valvetrain and ported stock heads. A last minute decision was made to install a new set of stainless steel, ceramic coated headers from G Body Parts. The stock units were rusty, cracked, welded, and beyond their years of service life, besides restricting airflow coming out of the motor. For now check out the power gains we made from the added airflow being able to move more rapidly through the Turbo Buick motor. We'll go for strip test results after the winter thaw melts the snow and ice from the track's surface.
The refreshed mill is returned...
The refreshed mill is returned to its original engine bay and held securely with new HR Parts N Stuff poly motor mounts we ordered from G Body Parts. These rugged units are designed for street/strip Turbo Buicks and are claimed to be stronger than solid mounts being able handle engines making upwards of 1,400 horsepower. Also noticeable is a new cam position sensor. It's a good idea to replace it as they are known to become faulty after years and miles of use.
From Part 5 you may remember...
From Part 5 you may remember the extensive port and polish handiwork that Jose Motor Sports performed. The Beehive valvesprings, titanium retainers, and Hi-Tech chromoly pushrods ensure valvetrain stability at high RPM. Additional help to move more air rapidly through the motor is Comp's hydraulic roller camshaft with 0.504/0.504-inch lift, 212/212 duration at 0.050. The stock wimpy cam (0.400/0.422-inch lift, 193/196 duration at 0.050) and valvetrain components couldn't complement the high flowing heads. On the valvetrain, only the sturdy stock rocker shaft assembly was reused. In the bottom end, the stock pistons, rods, and crank were cleaned-up and reused with new rings and bearings.
Another nice item from G Body...
Another nice item from G Body Parts are these Hye-Tech Perf. Stainless Steel ceramic coated headers. In these comparison shots it's obvious these beauties will easily outflow the stockers. They bolt right up to the stock type 3-bolt triangular flange turbo for easy fitment. It appears they'll improve exhaust velocity to the turbo for quicker spool-up. Not seen is the clamps and two-piece crossover pipe.
Seen here is the passenger...
Seen here is the passenger side header with the aforementioned 3-bolt flange bolted up to the Precision Turbo (58mm). Also noticeable is the stock location O2 bung with the O2 sensor installed right below the 3-bolt flange. For dyno testing we plugged into this bung for precise AFR (air/fuel ratio) mixture readings from the dyno's wide-band gauge. Tailpipe readings tend to be lean (0.3 to 0.5) after going through the turbo and exhaust system.
Here's the bad boy Buick V-6...
Here's the bad boy Buick V-6 after installation with all its accessories. Notice the stock intercooler, we plan to upgrade this unit later as it will certainly be a bottle-neck in our airflow, boost and power gains. Besides the new headers, under hood is all the same, just cleaner looking. During shake down street driving we noticed a smoother running motor without the V-6 stumble. At WOT, boost was only holding at 14 psi. With less backpressure and more air freely flowing through the motor, we lost roughly 5 psi of boost. This is a normal occurrence on a forced induction motor when high-flow heads, a better cam and/or headers replace manifolds. After a brief break-in period (about 100 miles) we figured we could safely raise the boost back to 19-20 psi while dyno testing.
We revisited our friends at...
We revisited our friends at Tune Time Performance to learn our gains and to be sure we had a safe air/fuel mixture before cranking up the boost. We were pleased to know that at only 14 psi we had the same horsepower (288 rwhp) as our last dyno test with 19.5 psi. Naturally, we had less torque with roughly 5 psi less boost. With the AFR at a safe 11.3 we would try to raise the boost a couple psi and see what happens.