Intake Manifold FAQ

1. Which is the best intake to run?

As with the choice of cylinder heads, there is not just one answer to this question. In order to correctly choose the best intake for your application, we need to understand your engine combination and rules. Thus, the best intake for a 355, flat tappet 2 barrel car that weighs 3,200 pounds and sees a maximum or 6000 rpm is not the best intake for a 406, 4 barrel and a roller cam running 7,400 rpm.

Also, many tracks have specific rules concerning the intakes. For these reasons we need to go over your combination to make the best recommendation. It only takes a 5 to 10 minute phone conversation for us to recommend the correct intake for your application.

Head Questionnaire: It asks all the right questions. Fill it out online here.

2. I run a 2 barrel carburetor. Should I run a 2 barrel or a 4 barrel intake?

When a 2 barrel carburetor and adapter is bolted to a 4 barrel Q-Jet intake, you have just about the same air flow as a 2 barrel intake. The Q-Jet intake will have a bit more internal volume than the 2 barrel manifold, which will soften the off the corner throttle response a bit. As a general rule the 2 barrel intake will be better for application that put a real premium on off-the-corner performance like a 3,200 pound car on a tight race track.

Dyno tests have found that a Q-Jet intake will produce 4 to 8 more horsepower above 5,500 rpm than a 2 barrel intake. The 2 barrel intake will produce about 5 more foot pounds of torque below 5,000 rpm. If you may someday be able to run a 4 barrel carburetor at a different track or at special end-of-the-year shows, the 4 barrel intake may be a wise choice.

3. Which is the best stock, untouched cast iron Small Block Chevy intake manifold to run?

Several years ago, we built a unique fixture with sliding doors to so we could flow test just the intake manifolds on our SuperFlow 600 bench without having to attach the intake manifold to a cylinder head. This fixture allowed us to flow test intakes very quickly and accurately. We flow tested at 28″ of water, with a radius flow guide on top of the plenum area. All of the 150, or so, stock intakes that we tested flowed between 160 & 165 cfm per runner, when the flow numbers for all 8 ports were averaged. With such a small variation in stock flow numbers we have concluded that “there is not much difference from one stock intake to another.”

If you are looking for a substantial improvement in airflow and thus horsepower, the cross-sectional area of the manifold must be significantly increased. For instance, when tested with the same flow testing procedure as the stock manifold, our Acid Ported intake flows 180 cfm, Stage 1 Ported intake flows 185 to 190 cfm and Full CNC Ported  intakes flow over 215 cfm.

 4. What is the best cast iron intake to run on Vortec or Vortec Bow Tie cast iron cylinder heads?

The best intake manifold for Vortec style heads is our Marine High-Rise intake. 2 and 4 barrel style intake manifolds are available. These intakes are not manufactured by Chevrolet.

Chevrolet makes a “Pancake” 4 barrel Q-Jet intake, part# 14097499. This intake was designed for a low rpm engine used on generators.  Running this intake on a race motor is like going to prom with your sister.  The performance of this intake will be 15 to 20 horsepower below a standard Q-Jet intake. For this reason, we do not recommend the “Pancake” intake.

To run a standard bolt pattern intake manifold on Vortec heads, the bolt pattern on the heads will have to be altered.

 We also check to make sure the intake “mechanically” fits properly. We may have to enlarge the intake manifold to cylinder head bolt hole or remove material from the end rails to make the intake fit properly. This way when you get the heads and intake they will fit properly.