Back in the last episode, we gained 50 rwhp by swapping to high-flow ported heads (Jose Motor Sports) and a hydraulic roller cam (Comp Cams). Our power gains were quite impressive considering there was roughly a 3 psi loss of boost. Apparently the 58mm Precision turbo we installed in Part 3 was a great upgrade for the stock cam and heads at the time, but could not support enough air volume for the latest higher-airflow combination. This proved it necessary for a move up to a larger turbo in order to restore boost and find out what the real gains would be at the same boost (20 psi). We called the tech line at Precision Turbo with the specs of our new combination and explained the boost loss. They recommended we use the new 6262B (62mm) unit that would restore boost and even give us the option to crank it up further. To maintain a stock-like underhood appearance, we ordered a stock intercooler with a fatter Duttweiler neck-end from G Body Parts. These two bolt-ons would bring back boost while moving more air rapidly to team up with the high-flow heads and roller cam from Part 6.
Precision Turbo recommended...
Precision Turbo recommended a step-up to their 62mm Dual Ceramic Ball-bearing Turbo (PTB300-6262B) from the previous 58mm unit, which worked well with the stock heads and cam. This new 62mm unit will provide the needed airflow volume and boost since switching to the well ported heads (Jose Motor Sports) and Comp Cams hydraulic roller cam (0.504/0.504-inch lift, 212/212 duration at 0.050.) in Part 6.
During the winter GN owner Tim Cairone found a local deal on an ‘87 3.8L short-block. He couldn't pass it up. It was a complete balanced assembly with forged JE pistons and H-beam Eagle rods. Downtime during the cold winter months was a perfect time at Tim's shop (Shore Wheels, Tuckerton, NJ) to swap out the short-blocks. Sure, the balanced, lighter/stronger, rotating/reciprocating parts will add a few horsepower to our test results, but will also be more durable for future dyno and track duties. Once the V-6 was running with the new 62mm Precision turbo and Duttweiler necked, stock intercooler, it was broken-in for roughly 300 miles with 18 psi boost.
Once again we visited our friends at Tune Time Performance for dyno testing and to tune for a safe AFR (air/fuel mixture ratio) before turning up the boost. Our buddy Matt Hauffe (Tune Time's owner and tuning expert) would be at the wheel of Tim's GN handling dyno duties. On the first pull we were pleased to find gains in power (19 hp, 24 lb-ft) at 18 psi boost (lowest boost from 62mm turbo) compared to the smaller 58mm turbo (17.5 psi, most boost from 58mm turbo). By following Precision's recommendations we benefited with the right size turbo to match the airflow volume needed for our combo. Follow along the captions and check the charts and graphs to see the big-time gains realized by sorting out a well matched combination. In our next episode we'll be back to track-test Tim's efficient street cruiser.
This pretty power adder features...
This pretty power adder features a 62mm billet compressor wheel, "E" compressor cover (housing) with a 3-inch inlet/2-inch outlet. The turbine housing is a Buick 3-bolt, .63 A/R with a 62mm turbine wheel.
G Body Parts offers a stock...
G Body Parts offers a stock intercooler upgraded with the wider Duttweiler neck welded-on. It will increase the flow of the compressed/boosted air coming out of the turbo.
In these comparison shots...
In these comparison shots there's a noticeable size difference in the necks. Stock is 2 inches while the Duttweiler neck is 2 1/2 inches.
Tim scored a local good-guy...
Tim scored a local good-guy deal on this forged component short-block. It consisted of JE forged 0.020-inch over pistons and Eagle H-beam rods.
The stock crank was machined,...
The stock crank was machined, polished, and balanced to the lighter and stronger reciprocating assembly.
These forged/balanced internals...
These forged/balanced internals will add durability to the little V-6 while enabling it to hold up better to high boost (over 21 psi) conditions, dyno and track beatings.