This is the TBSS that we’ve used on several engines during dyno testing. We’ve outfitted it here with custom brackets to mount a Holley fuel rail. The throttle body mount is a four-bolt so there are plenty of options including Holley’s affordable Sniper 92mm unit. (Image/Jeff Smith)

I’ve heard there is a really good factory LS intake manifold out there for cathedral port intakes but the friend who mentioned it didn’t know anything more than that. He said it was from a truck or an SUV but he wasn’t sure. Do you know what he’s talking about? I have a ’69 Chevelle that I’m about to put an iron 5.3L into. The engine is stock but I’m thinking of ways to make a little more power. Does this manifold exist? If so, where do I get it?


The intake that I think you are referring to is the GM Trailblazer SS intake. This was stock on the 6.0L Trailblazer SS model SUV. The SS models came with LS2 truck engines that were equipped with a different intake manifold than the car version, and it works very well.

Our buddy Richard Holdener has probably done more LS engine dyno comparative testing than anybody we know. He compared that Trailblazer intake to both the stock, cathedral port truck intake, and the LS6 Corvette intake. The truck intakes were designed to enhance low-speed power in the rpm range where trailer towing puts a heavy emphasis on torque. Conversely, the early LS Corvettes and Camaros used a much shorter intake that gave up a little torque to make more peak horsepower.

The Trailblazer SS (TBSS) intake is tall like the early truck manifolds but a little wider. The GM engineers did their homework on this intake as Holdener discovered. The TBSS will make more torque than the earlier truck intakes and yet will make more horsepower than the old LS6 intakes. The biggest issue with the TBSS is its height, which means it can be a tight fit with the hood closed.

I’ve never measured the clearance for an LS swap in a second generation Chevelle like yours but I do know that this manifold will clear the stock hood of the first generation ’64-’67 Chevelles. My guess is that the Trailblazer SS intake would also fit under your hood line. Of course, EFI means several other changes to your car. But first, let’s answer your question about where to get this intake.

The good news is that you can buy this as an AC Delco part straight out of the Summit Racing catalog for a good price considering it’s a brand new composite AC Delco part. This manifold is bare which means you will need fuel rails, injectors, a throttle body complete with sensors, and a MAP sensor. If you already have a stock truck intake on your 5.3L engine, then you can adapt the injectors and probably the MAP sensor too.

The factory fuel rail is unique to this intake and rather than buy a new one (which might be expensive and will still need to be adapted to the fuel delivery system), we converted our TBSS over to use LS1/LS6 aluminum fuel rails from Holley. The Sniper fuel rail kit is affordable but it does not include mounts for the TBSS intake. We made our own out of 0.120-inch sheet aluminum. The brackets end up in a Z-shape to bolt between the fuel rail and the manifold and are easy to make.

Be aware however that adapting fuel rail mounts can be hazardous from a fuel leak standpoint because if the mounts are not accurate, the injector can leak between the fuel rail and the injector o-rings in the fuel rail. Fuel leaks with a system designed to run at 43 to 58 psi is very dangerous. So if you are going to do this, be sure to test the system first and then keep an eye on the mounts for the first few hundred miles to make sure the mounts properly retain the fuel rail. Fuel leaks are nothing to trifle with and can very dangerous–so be careful.

The TBSS intake also will require a 4-bolt mounting throttle body. The early truck manifolds used a 3-bolt throttle body so it will not transfer–unless you want to purchase an adapter. We’ve listed one from ICT Billet in the parts list section. The least expensive 4-bolt throttle body we found is a Holley Sniper 92mm version. This throttle body will need a TPS sensor and an idle air control motor to make it completely functional.

With the throttle body and fuel rails installed using the stock truck fuel injectors, you will still need an EFI controller. A factory ECU is certainly an option, but if you plan on further modifications to the engine, drivability will suffer unless the system is tuned. Paying someone to tune it may cost as much as buying an aftermarket EFI system. FiTech sells a stand-alone harness that uses its self-learning ECU and software to control a Gen III or IV LS engine. However, the harness is intended to plug into EV1-style injectors that are not the same electrical connector as the factory injectors. If you are retaining the stock 5.3L injectors, you will need adapters to connect the FiTech harness to the GM injectors.

These stand-alone systems come with or without automatic transmission control. So if you are considering running a 4L60E behind your 5.3L motor, the unit with the transmission control will also plug into the transmission. The advantage here is that you will not need a separate controller for the transmission as the FiTech ECU will control both the engine and the transmission.

With a stock or mild camshaft (under 230 degrees at 0.050), the self-learning software will work very well and will establish good part-throttle and WOT tuning very quickly. This might be a great way to approach this engine package that will also be up and running very quickly.


Chevy Trailblazer Intake Manifold Upgrade Parts

PartPart Number
ACDelco Trailblazer SS Intake ManifoldADO-12580420
Holley Sniper 4-bolt Throttle Body, 92mmHLY-860004-1
Holley Sniper LS1 Billet Fuel Rail Kit HLY-850001
ICT Billet Throttle Body AdapterICB-551511
FiTech Standalone ECU and Harness, w/o Trans.FIF-70050
FiTech Standalone ECU and Harness, w/Trans.FIF-70051


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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.