All the Torques: How Summit Pro LS Truck Camshafts Help Truck Owners Maximize Performance

It’s no secret that yanking a Gen. 3 or Gen. 4 Vortec truck engine out of the junkyard is the cheapest way to make 400+ horsepower.

5.3L engines start in the $600-$1,000 range and go up to a little more than $2,000 for the 6.0L and 6.2L engines. These engines made 270-400 hp from the factory will run smooth as silk for over 300,000 miles (unless you have AFM).

Before we get into truck cams, here’s a bit of trivia: Engines like the LS1, LS6, LS3, LS7, LSA, and LS9 are what most people think “LS” engines are, but did you know there are 27 different variants of Gen. 3 and Gen. 4 truck engines that are members of the LS engine family?

There were seven Gen. 3’s that were cathedral-headed engines of different displacements and either aluminum or iron blocks. The 20 different Gen. 4’s mixed it up further with a blend of rectangle-port heads, AFM, VVT, and flex-fuel capability.

*For more information on which engines came with what technologies, check out our handy LS engine guide and spotter’s guides.

We’ve also talked about whether you want to maintain VVT. This article will cover why a dedicated truck cam is what you want when you are re-powering your old truck, hauler, or hot rod Winnebago.

First, these engines have heads, intakes, and a bottom-end good past 7,000 rpm. Engine rpm is power, but the key to truck cams is not losing your bottom-end torque in pursuit of a peak horsepower number. Why? Acceleration is maximum average horsepower through the rpm range. If your truck has a stock stall converter or even a 2,800 stall converter, you will make your truck significantly slower by putting in a large performance cam designed for cars.

Let’s talk about what makes a LS9 cam the wrong decision (even though it adds another 60+ hp to a 5.3L). It specs out at 211 intake and 233 exhaust duration. It has a very wide 122.5 lobe separation and is ground 1-degree retarded.

Lift is .562/.558. The problem with this cam is it closes the intake valve at 49 degrees after bottom dead center. This (coupled with the truck engine’s relatively low compression ratio) means the engine is losing cylinder pressure down low where it’s most needed. As much as much 40 ft.-lbs. worth at 2,500 rpm.

What did the factory do to maximize power down low? There are a couple of truck cams that stand out. The LQ9 cam was shared with the LS1 (2001-02 F-body version). It specs out at 196/208 116 LSA and .467/.479 lift. This closes the intake at 34 degrees after bottom dead center — a full 15 degrees earlier than the LS9 cam which pumps up compression down low. In a 5.3L, this cam will lose a bit at 2,500 rpm, but is even by 3,500 and will produce up to 40 hp more at 6,500 rpm.

The other cam that is technically a truck cam is the LS2 as used in the Hot Rod TrailBlazer SS. This cam specs out at 204/211 117 LSA with -4 advance and .524 lift. The closes the intake at 43 degrees after BDC. The result? It bleeds off compression — as much as 20 ft.-lbs. at 2,500 rpm, but makes up for it higher in the rpm range. As much as 70 hp at 6,000 rpm.

So how does an aftermarket truck cam improve upon these car cams?

First, is with more lift.

Lift is free power from idle on up. Secondly, the intake valve can be open much sooner. What does this do? Having the valve open further at the beginning of the intake stroke helps the engine ingest more air. More air is more compression. More torque and power are the result. The downside? The earlier you open the intake valve, the lopier the idle gets. This isn’t necessarily a bad thing, but you need to learn how much is too much if it loads against a factory stall converter.

More on Summit Pro LS Truck Cams

Let’s take a look at the Summit Pro LS truck swap cams. These are designed to be easy on the valvetrain. They are designed in stages 1 through 4 depending on the idle quality you’re looking for. They close the intake valve anywhere between 33 degrees after BDC with the SUM-8718 towing/efficiency cam to as late as 41 degrees in the biggest SUM-8714 stage 4 cam.

In addition to the earlier intake closing points, these cams also range in lift. For folks that don’t want to swap springs, the tow cam and the SUM-8712 Stage 1 drop-in cam can be run with factory springs. Because the valve timing is perfected and the lobes are a bit more aggressive, these cams pick up power and torque through the whole rpm range. These cams can also increase fuel efficiency. How is this? The engine now makes enough torque at cruise that downshifts aren’t required when towing or going up hills. Less rpm means less air and fuel ingested.

Next up are the mid-lift cams. Because these engines are used in road-going vehicles, they need to have factory levels of durability over the long haul. To that end, what’s better than a LS6 spring?! The LS6 made over 400 hp at over 6,000 rpm and did so for over 150,000 miles! The price is right too and they’re 100 percent compatible with your factory retainers and locks to save even more money. Summit designed their Stage 2, 3 and 4 cams around these springs.

Next up is the SUM-8720 .600 lift cam. This cam is unique in that it’s designed around a .600 lift TFS-16918-16 beehive spring. This spring also increases seat pressure to 130 lbs. of seat pressure and 318 lbs. of open pressure to increase the rpm range without being hard on the factory valvetrain. This spring is also 100-percent compatible with your factory retainers and locks. The specs on this cam are 218/227 112 + 2 .600/.600. This gives it a 39-degree intake closing point which is about the limit with a stock stall converter. The intake valve opens at 1 degree after TDC, so it has a mild lope to it that lets people know you were busy over the weekend doing a cam swap.

Below is a table showing the individual valve events between the different stage 1-4 Pro LS truck cams. You’ll see how the intake closing and opening points are done in specific increments to give you exactly the power and attitude you’re looking for out of your truck.

Although the Pro LS cams come with different cam/spring/and gasket kits, here’s a list of other components you may want to consider depending on the age of your engine.

• Trunnion kits (both bearing style and bushing style) have done a lot to increase durability. Summit Racing has LS1 and LS3 rockers that come assembled with their corresponding trunnion kits right out of the box. This saves the cost of a trunnion installation tool and it can save precious hours if you’re paying a shop to do the work.
• Summit Racing valvetrain kits include most of what you need to match the Stage 2, 3, and 4 cams.
• Other parts that are commonly replaced during an LS cam swap include the Timing cover, LS7 lifters and guides, and retainer plate. Timing chain dampers are a big plus to reduce chain whip and the chance of chain breakage. Although complete timing sets are available, many find the gears in good shape and just go with a LS2 chain.
• AFM lifters can fail periodically. When they do, performing a cam swap along with AFM and VVT delete kits is a smart move.

If you want to learn more about specific valve events and how they affect engine behavior, check out this article on considering individual timing events when selecting a camshaft.