FLAG Motorsports Mach V Ported Gen V LT Cylinder Heads
More power. Less boost. More room to grow.
Boost tells you how much pressure is in the intake manifold, but it doesn’t tell you how much air made it through the engine.
That distinction became hard to ignore during our planning and execution of the 2026 LT4 Camshaft Shootout. One of my favorite parts of that event was the “build up” phase where we slowly went from our stock 684hp baseline to a 1,006hp screamer with some simple modifications. Cam, Boost, Heads, X-Port.
What I love about these heads (aside from the power) was the fact FLAG Motorsports had been silently developing them over the past 2-3 years making small but impactful improvements, refining their CNC porting design, valve job blending, and flow bench testing, in order to ensure their new Mach V Cylinder Heads were one of the highest flowing, and most powerful head porting service on the market.
Having one of the best set of ported cylinder heads for the Gen. V LT platform is great, but not being able to get them in the hands of those in need, is a logistical issue most of the competition has been struggling with for years. Which is why we LOVE that Flag offers these heads as a complete buy-out (you keep your heads) or as a core exchange program, where we ship you the new assembled heads, and you ship yours back for a core exchange credit. This is a key advantage for those who don’t have the 3-4 weeks to ship your heads in for the traditional porting service, and need parts NOW.
What did the heads gain on the engine dyno?
We performed same-day A/B tests at Westech on a stock-displacement 6.2L LT4 engine. The camshaft and other test variables stayed the same, and the same valve springs were transferred between the stock and Mach V heads.
Adding the MACH V heads to our LT4 with Stage.3 cam and stock blower picked up… +56 peak hp, +66 lb-ft at peak torque, and 240 RPM more peak-power carry.
Adding the MACH V heads to our LT4 with Stage.3 cam and KONG Ported blower picked up… +100 peak hp, +41 lb-ft at peak torque, and 600 RPM more peak-power carry.
Those peak figures do not tell the whole story. In the unported-blower test, we saw as much as 78 lb-ft more torque near 4,000 RPM. With the ported blower, the advantage grew to more than 85 lb-ft near 7,000 RPM.
The takeaway from our camshaft shootout is that a cylinder head is more than a finishing touch for a high-output LT4, and they are worth WAY more than the 25rwhp the internet will tell you about. As the cam and blower move more air, the factory heads can become a massive restriction. The Mach V heads gave our combinations a stronger path to make power and carry it higher in the RPM range.
What makes a Mach V head?
Each Mach V head receives:
Aggressive 5-axis CNC porting of the intake and exhaust runners
Precision deck surfacing for a perfect MLS head gasket seal
Ported and softened 62 cc combustion chambers
Performance valve job with bowl blending
Bolt holes for both an LT4 supercharger and an LT1 intake manifold, supporting boosted and naturally aspirated LT builds
Build the heads for the way you drive.
Mach V heads are available with different valve seats, valves, and spring hardware to meet your needs. The right combination depends on your camshaft, boost, RPM range, and whether the car spends its life on the street, drag strip, or road course.
VALVE SEATS: We have some cool options here to meet your needs from mild to wild.
OEM powdered-metal: If desired, we will ship your ported heads with factory OEM seats as the most cost effective option. Although GM did a good job on these heads from the factory, FLAG has seen alot of OEM seat failures ranging from chipped seats, or fall out, which is why we cannot be liable for failed powdered metal seats as it is a known factory defect.
Ductile Iron Seats: These seats are a stronger replacement option to ensure the seats in the heads can hold up better to high lift camshafts or camshafts with aggressive ramp rates. If you have a large or high lift camshaft we highly recommend these seats over the stock seats to prevent chipping.
AMPCO45 & CHE BX: These are the nicest possible seat materials on the market. We recommend these for road racing or any sustained high RPM applications, especially with titanium valves. The main advantage is the thermal conductivity of the seat is much higher, as the seat is the main path for heat to travel out of the valve. This helps keep your valves cooler, which increases longevity and reliability, as well as increasing the tuning window for timing by reducing detonation risk. AMPCO 45 is a nickel-aluminum bronze alloy, and it is used on the intake seats. CHE BX is a proprietary copper-bronze alloy valve seat material made by CHE Precision specifically for the exhaust side of high-performance and racing engines.
Valves: Choose factory GM valves for mild boosted applications or N/A. For higher HP boosted applications we always recommend Ferrea Super Alloy intake valves with Inconel exhaust valves due to the higher heat resistance and better material quality.
Springs: Flag offers a USA made dual spring kit for these cylinder heads, rated for .700” lift. The springs are 165lbs on the seat (closed pressure) and open pressure at .700” lift is 490lbs. Coil bind is .980. The kit has two retainer options, Chromoly and Titanium.
Chromoly retainers are recommended for lower RPM applications such as street cars.
Titanium retainers are recommended for higher RPM or racing applications due to weight.
Cores: Purchase outright for only $1,000 more, or send us back your used LT4 or LT1 heads in good condition and save $1,000.
More power throughout the pull. With our KONG-ported 1.7L blower combination, the Mach V heads delivered an average gain of 55.9 horsepower and 53.4 lb-ft across the shared 4,000–6,800 RPM test range. Peak engine horsepower climbed from 906.3 to 1,006.4 while peak boost dropped from 16.1 to 15.8 psi. That means the benefit extended well beyond a single peak number—you get a stronger power curve across the RPM range we tested.
Compression: The Mach V heads feature 62 cc combustion chambers, which when used with OEM head gasket thickness will raise a stock LT4’s compression ratio from 10.0:1 to approximately 10.45:1. That modest increase will improve torque, throttle response, and overall combustion efficiency, helping your engine make better use of each air-and-fuel charge. Builds running ethanol blends or suitable high-octane fuel are particularly well positioned to take advantage of the added compression. Final compression depends on your pistons, head gaskets, and deck height, and the calibration should account for your fuel, boost, and intended use.
The right heads for your next stage
Whether you are planning a head-and-cam package around a max-effort 1.7L blower build or leaning towards a bigger cube larger blower power plant, the Mach V heads will give your engine more airflow to work with, which will gain HP and drop boost at the same time. Our shootout showed why that matters, and the results speak for themselves.
Tell us your current cam, supercharger, pulley combination, fuel, and intended use. Griffin Motorsports can help you choose the seat, valve, and spring configuration that fits the complete build.
FLAG Motorsports Mach V Ported Gen V LT Cylinder Heads
More power. Less boost. More room to grow.
Boost tells you how much pressure is in the intake manifold, but it doesn’t tell you how much air made it through the engine.
That distinction became hard to ignore during our planning and execution of the 2026 LT4 Camshaft Shootout. One of my favorite parts of that event was the “build up” phase where we slowly went from our stock 684hp baseline to a 1,006hp screamer with some simple modifications. Cam, Boost, Heads, X-Port.
What I love about these heads (aside from the power) was the fact FLAG Motorsports had been silently developing them over the past 2-3 years making small but impactful improvements, refining their CNC porting design, valve job blending, and flow bench testing, in order to ensure their new Mach V Cylinder Heads were one of the highest flowing, and most powerful head porting service on the market.
Having one of the best set of ported cylinder heads for the Gen. V LT platform is great, but not being able to get them in the hands of those in need, is a logistical issue most of the competition has been struggling with for years. Which is why we LOVE that Flag offers these heads as a complete buy-out (you keep your heads) or as a core exchange program, where we ship you the new assembled heads, and you ship yours back for a core exchange credit. This is a key advantage for those who don’t have the 3-4 weeks to ship your heads in for the traditional porting service, and need parts NOW.
What did the heads gain on the engine dyno?
We performed same-day A/B tests at Westech on a stock-displacement 6.2L LT4 engine. The camshaft and other test variables stayed the same, and the same valve springs were transferred between the stock and Mach V heads.
Adding the MACH V heads to our LT4 with Stage.3 cam and stock blower picked up… +56 peak hp, +66 lb-ft at peak torque, and 240 RPM more peak-power carry.
Adding the MACH V heads to our LT4 with Stage.3 cam and KONG Ported blower picked up… +100 peak hp, +41 lb-ft at peak torque, and 600 RPM more peak-power carry.
Those peak figures do not tell the whole story. In the unported-blower test, we saw as much as 78 lb-ft more torque near 4,000 RPM. With the ported blower, the advantage grew to more than 85 lb-ft near 7,000 RPM.
The takeaway from our camshaft shootout is that a cylinder head is more than a finishing touch for a high-output LT4, and they are worth WAY more than the 25rwhp the internet will tell you about. As the cam and blower move more air, the factory heads can become a massive restriction. The Mach V heads gave our combinations a stronger path to make power and carry it higher in the RPM range.
What makes a Mach V head?
Each Mach V head receives:
Aggressive 5-axis CNC porting of the intake and exhaust runners
Precision deck surfacing for a perfect MLS head gasket seal
Ported and softened 62 cc combustion chambers
Performance valve job with bowl blending
Bolt holes for both an LT4 supercharger and an LT1 intake manifold, supporting boosted and naturally aspirated LT builds
Build the heads for the way you drive.
Mach V heads are available with different valve seats, valves, and spring hardware to meet your needs. The right combination depends on your camshaft, boost, RPM range, and whether the car spends its life on the street, drag strip, or road course.
VALVE SEATS: We have some cool options here to meet your needs from mild to wild.
OEM powdered-metal: If desired, we will ship your ported heads with factory OEM seats as the most cost effective option. Although GM did a good job on these heads from the factory, FLAG has seen alot of OEM seat failures ranging from chipped seats, or fall out, which is why we cannot be liable for failed powdered metal seats as it is a known factory defect.
Ductile Iron Seats: These seats are a stronger replacement option to ensure the seats in the heads can hold up better to high lift camshafts or camshafts with aggressive ramp rates. If you have a large or high lift camshaft we highly recommend these seats over the stock seats to prevent chipping.
AMPCO45 & CHE BX: These are the nicest possible seat materials on the market. We recommend these for road racing or any sustained high RPM applications, especially with titanium valves. The main advantage is the thermal conductivity of the seat is much higher, as the seat is the main path for heat to travel out of the valve. This helps keep your valves cooler, which increases longevity and reliability, as well as increasing the tuning window for timing by reducing detonation risk. AMPCO 45 is a nickel-aluminum bronze alloy, and it is used on the intake seats. CHE BX is a proprietary copper-bronze alloy valve seat material made by CHE Precision specifically for the exhaust side of high-performance and racing engines.
Valves: Choose factory GM valves for mild boosted applications or N/A. For higher HP boosted applications we always recommend Ferrea Super Alloy intake valves with Inconel exhaust valves due to the higher heat resistance and better material quality.
Springs: Flag offers a USA made dual spring kit for these cylinder heads, rated for .700” lift. The springs are 165lbs on the seat (closed pressure) and open pressure at .700” lift is 490lbs. Coil bind is .980. The kit has two retainer options, Chromoly and Titanium.
Chromoly retainers are recommended for lower RPM applications such as street cars.
Titanium retainers are recommended for higher RPM or racing applications due to weight.
Cores: Purchase outright for only $1,000 more, or send us back your used LT4 or LT1 heads in good condition and save $1,000.
More power throughout the pull. With our KONG-ported 1.7L blower combination, the Mach V heads delivered an average gain of 55.9 horsepower and 53.4 lb-ft across the shared 4,000–6,800 RPM test range. Peak engine horsepower climbed from 906.3 to 1,006.4 while peak boost dropped from 16.1 to 15.8 psi. That means the benefit extended well beyond a single peak number—you get a stronger power curve across the RPM range we tested.
Compression: The Mach V heads feature 62 cc combustion chambers, which when used with OEM head gasket thickness will raise a stock LT4’s compression ratio from 10.0:1 to approximately 10.45:1. That modest increase will improve torque, throttle response, and overall combustion efficiency, helping your engine make better use of each air-and-fuel charge. Builds running ethanol blends or suitable high-octane fuel are particularly well positioned to take advantage of the added compression. Final compression depends on your pistons, head gaskets, and deck height, and the calibration should account for your fuel, boost, and intended use.
The right heads for your next stage
Whether you are planning a head-and-cam package around a max-effort 1.7L blower build or leaning towards a bigger cube larger blower power plant, the Mach V heads will give your engine more airflow to work with, which will gain HP and drop boost at the same time. Our shootout showed why that matters, and the results speak for themselves.
Tell us your current cam, supercharger, pulley combination, fuel, and intended use. Griffin Motorsports can help you choose the seat, valve, and spring configuration that fits the complete build.
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