The past four years have been great in the life of bowtie6. The car has performed flawlessly logging almost 15,000 miles. Several major improvements have been made:
Cam & Rockers
The stock cam has been replaced with a high-lift ratio. The specs on the cam explained the change would take effect in the 1200-1500rpm range and last until redline. This was to give a much smoother powerband. In additiont to the high lift cam, a set of roller rockers has been installed along with a set of matching performance valve springs.
I was able to find a set of lightly used heads for this engine. They were taken to a local machinist and he ported, polished and flowed the heads. A three angle valve job was also performed. The intake ports on the stock heads has a ‘sharkfin’ to help promote air flow. While this improves low-rpm flow, it restricts flow at higher rpm ranges. The fins were completely ground off and this made a huge difference. All intake ports were matched to the lower intake manifold and the exhaust ports matched to the custom headers. There is definitely truth in the statement that “horsepower is in the heads”.
The stock intake had been re-worked once by installing the throttle body from an LT1 V8. This basically replaced the single butterfly with two large butterflies on the intake. However, the rest of the intake was still very restrictive. So, the intake was re-worked yet again making it handle a large amount of air volume. To improve airflow as much as possible an airfoil for the throttle body was installed.
The cam and intake modifications made a great difference. Soon after that was all done, I took the car to a local dyno for measurements. The total figures produced 153hp at the rear wheels with 189ft/lb torque. Quite respectable numbers.
Then came the heads. Wow! What a difference. The upgrade bumped up power to 188hp at the rear wheels and 226ft/lb torque. At the dyno, the exhaust gas was analyzed with an O2 sensor and was found to be spot-on. On the first dyno session the ECM was not making things very efficient at higher RPM’s. With the new heads, larger injectors and an adjustable fuel pressure regulator we were able to get much more efficient results. This made the extra power at the wheels.
Unfortunately this is the end-of-the-line for the 3.4 litre V6. The ECM on this engine is OBD1 and not tunable. That is why we had to fiddle with the AFPR and run bigger injectors. The powerband on this engine is very smooth and redline can be achieved right quickly.