Look what Mark did for this...
Look what Mark did for this intake plenum. By cleaning up rough edges and irregular passages, he witnessed tremendous gains in flow.
For our Budget 347, Mark port-matched the intake manifold and cylinder heads to achieve smooth airflow. This is one of the single greatest steps you can take when building a street driver small-block. Port matching and cleaning up the runners yields abundant airflow, as proven by our chart. Mark achieved a whopping 26.45 percent and 81.7 cfm on his best runner with port work. He also cleaned up the plenum, which improved flow.
Port matching doesn't take...
Port matching doesn't take much effort. All you have to do is get intake ports, runners, and gaskets on the same page. This reduces and even eliminates turbulence.
The Edelbrock Victor Jr. cylinder...
The Edelbrock Victor Jr. cylinder head for 351W-based engines can also be installed on the 289/302 engine by utilizing cylinder head bolt spacers with smaller head bolts. Trans Am Racing has taken this proven high-performance cylinder head and improved flow dramatically with port and bowl work. Gains as high as 28 percent intake and 34 percent exhaust have been achieved via Mark's efforts.
These larger 70cc high-swirl...
These larger 70cc high-swirl combustion chambers are important to consider when choosing cylinder heads. Mark took this into account when he was selecting pistons. Check out Mark's finish work in this chamber.
What Is Rocker-Arm Ratio?
With 1.7:1 Comp Cams Magnum...
With 1.7:1 Comp Cams Magnum roller rockers and the Parker manifold, we gained 7.3 hp and lost 1 lb-ft of torque. As expected, the additional valve lift increased horsepower but didn't do anything for torque.
There are two kinds of lift-lobe lift and valve lift. Lobe lift is maximum lift or rise at the cam lobe. For example, if lift is 0.450-inch lobe lift, the lobe itself gives us 0.450-inch (nearly 1/2-inch). Valve lift is what the cam lobe and rocker arm combined give us via the pushrod. If we're running a 0.450-inch lift cam with a 1.6:1 rocker arm, we're getting 0.720-inch or nearly 3/4-inch. Rocker ratio-1.6:1-takes 0.450-inch cam lobe lift and multiplies it 1.6 times. When stepping up to a 1.7:1 rocker ratio, we're taking cam lobe lift and multiplying it 1.7 times.
Edelbrock Performer RPM Air Gap intake manifold, 830-cfm Holley 4150, and 1.6:1 Trick Flow Specialties rocker arms
Switch to 1.7:1 Comp Cams Magnum rocker arms with Edelbrock Performer RPM Air Gap intake and 830-cfm Holley 4150
Mark tried different carburetor...
Mark tried different carburetor spacers to see what happens to horsepower and torque. With the Parker manifold, there wasn't much difference because the manifold has a natural bend toward velocity right out of the box with just the right amount of plenum for high rpm use.
Parker single-plane, long-runner intake manifold, 830-cfm Holley 4150, and 1.6:1 TFS rocker arms
Parker intake manifold w/1.7:1 Comp Cams Magnum rocker arms