A lot of people treat the Cummins cylinder head like a hard airflow wall. It isn’t. Yes, the head is a restriction, but it is not the only restriction, and it is not the point where airflow upgrades stop mattering. A stock 6.7L Cummins is already pumping 331 CFM at 2,800 RPM, and with more RPM and enough turbo, airflow goes much higher. On the flow bench, we ran a stock head through the Banks Monster-Ram Intake and Killer Grid Heater Upgrade and saw 750 CFM. That was the limit of the bench, not the limit of the head or the intake path. The takeaway is simple: the ‘head is the major restriction, so the intake elbow does nothing’ argument does not hold up. Open up the inlet path and the engine can use more air.
The video opens with Gale responding to viewer comments about the Banks Monster-Ram for the Cummins. Several commenters argue that the product cannot improve airflow because, in their view, the cylinder head is the engine's dominant restriction. One comment claims the Monster-Ram "does nothing" because "the head is the major restriction." Another insists that the stock intake horn already outflows the stock head, implying that replacing the horn or elbow cannot matter. A third comment states that a Cummins head will not even flow 250 CFM, while the stock horn supposedly exceeds that figure, so any added intake capacity would be meaningless.
Gale's objection is not simply that the comments are negative, but that they are technically wrong in a way that misleads other readers. The central misconception is the idea that if the head is restrictive, then upstream intake improvements cannot produce gains. That logic does not hold. In a real induction system, multiple components contribute to total restriction, and reducing pressure loss ahead of the head can still improve the engine's ability to move air. If the head were truly the sole meaningful bottleneck, then changes to the turbocharger or intake elbow would produce no measurable effect. In practice, they do.
To ground the discussion in actual airflow demand, Gale cites the stock Cummins engine's displacement and operating speed. At 2,800 RPM, which he identifies as the horsepower peak, the engine pumps 331 CFM. That figure alone already challenges the claim that the head cannot flow even 250 CFM. He then notes that performance users often run the engine faster, in the neighborhood of 3,400 RPM or more. As engine speed rises, airflow demand rises with it, so the notion that the stock system's airflow requirements remain modest is not realistic for tuned or higher-RPM operation.
The discussion then moves beyond naturally aspirated-style assumptions. Gale explains that with enough turbocharger, the engine can easily flow more than 1,000 CFM. That point is important because turbocharged diesel airflow is not limited to the simple low numbers being quoted in the comments. Boost increases air mass flow substantially, and any component in the intake path that reduces restriction can affect how efficiently that air reaches the cylinders. The commenters' CFM claims therefore fail both at the level of basic engine demand and at the level of boosted operating conditions.
To support the argument with measured data, Gale refers to flow-bench testing. He acknowledges that a flow bench is not a turbocharger, but says it still illustrates the airflow capability of the parts in question. In testing through a Banks Monster-Ram, the stock head flowed 750 CFM. That result directly contradicts the assertion that the head will not flow 250 CFM. It also shows that the airflow capability of the system is far higher than the commenters suggest.
Gale is careful to explain what the 750 CFM figure does and does not prove. He says that 750 CFM is not the limit of the Monster-Ram, and it is not the limit of the cylinder head either. It is the limit of the flow bench used in the test. In other words, the test reached the equipment ceiling before reaching the airflow ceiling of the intake or head. That distinction matters because it prevents viewers from misreading the number as a hard cap on component performance.
The recap does not deny that the cylinder head is restrictive. Gale explicitly says that the head is a restriction. His point is that it is not the restriction in the absolute sense claimed by the commenters. Engines rarely have only one meaningful choke point. The intake horn, elbow, turbocharger, ports, valves, and head all interact as part of the total airflow path. Improving one section can still reduce overall pressure loss and improve delivered airflow, even when another section remains imperfect.
The practical conclusion is straightforward. If the head alone determined airflow and nothing upstream mattered, then upgrading the turbocharger or replacing the intake elbow would have no effect on performance. But those changes do have an effect, which demonstrates that the stock intake path is not irrelevant. That is the core of Gale's rebuttal to the online claims about the Monster-Ram. The stock head may be part of the restriction picture, but it does not make intake improvements useless. Based on the airflow calculations and the flow-bench result of 750 CFM through the stock head with the Banks Monster-Ram, Gale closes by declaring the criticism disproven: myth busted.
