What does lsa stand for cam

Things like idle vacuum, fuel economy, and tuning all factor into picking the right cam. Tight LSA cams make excellent low-end torque and have a beautiful power curve. But nothing comes without a cost, and idle vacuum suffers as LSA shrinks. This causes the engine's street manners and tuning to become fickle. A cam with a tighter LSA will require a looser torque converter, may not be able to run vacuum-assisted brakes, and doesn't play nice with fuel injection.

That lopey idle that is universally loved, and part of the allure of a tight LSA cam, is actually misfire caused from a combination of exhaust dilution in the intake manifold and poor cylinder filling at idle.

It creates an unsteady manifold vacuum condition that, on a fuel-injected engine, confuses manifold air pressure MAP sensors, making it hard for them to regulate fueling. The intake air control valve IAC , which regulates idle speed, also has to work overtime and often attempts to "catch" the idle, but usually shoots high or low. These issues can often be worked through by an advanced tuner, but always present a challenge and compromise in tuning strategy.

The world of fuel injection is where wide LSA cams like the really shine. With minimal overlap and a steady manifold vacuum signal, they work great with fuel-injection systems and are the norm on modern pushrod engines, such as the LS and Gen III hemi. If you're an OEM automaker looking for a steady idle, good fuel economy, and passing tailpipe emissions, this is the cam of choice.

Wide LSA cams are also applicable in forced-induction applications where less exhaust overlap is required. If you look at any given cam catalog, you will find that the majority of street-oriented cams fall in this range. That is no accident. A cam in the LSA range provides the necessary idle lobe to appease gearhead ears with acceptable manifold vacuum to run vacuum-operated accessories. Around 70 percent of muscle-car performance cams fall into this range. Cylinder-head flow and LSA are directly related: as a rule of thumb, the better the head flows, the wider the LSA can be.

A wider LSA moves intake- and exhaust-valve events farther apart and creates less overlap, which hurts intake-wave tuning. When you don't have any overlap, you can't have any wave tuning. A tighter LSA is always going to have more overlap, which allows the exhaust and intake system—if they're tuned well—to work together.

This wave tuning is what helps performance engines achieve volumetric efficiencies of more than percent. To overcome this inherent problem in wide LSA camshafts, you simply need a higher-flowing intake port. This is why the LS series, and many other modern engines, can make great power on top and bottom with wide LSA camshafts and why a plethora of factory cylinder heads are flowing near or above cfm.

Pinning the tail on the perfect cam can certainly be a difficult task. Ultimately, it comes down to how you want the engine to run, the car's intended purpose, and what you are willing to tolerate. Armed with more information on camshaft theory, what will you build?

Known as "The Gladiator" around Westech Performance, this Dart SHP blockbased, ci, small-block Chevy has made thousands of dyno pulls testing all manner of heads, intakes, cams, and every other crazy thing us magazine folk have coerced Westech's Steve Brul to bolt to it.

That notion is completely false. As you can see in the graph, the LSA cam actually had the highest cranking compression of the batch: psi. Call Russ Yoder of Erson M. I assume your engine to be small-block Chevrolet, so cam grinders should have easy access to an appropriate cam core. I have a ci sbc with a solid roller cam that ran well but noisy and a little problematic.

In it broke a rocker and more recently a valve spring. I am ready to make a change in valve train and go hydraulic roller and EFI but want to make as much power as possible: hp crank on pump gas. Mostly street-driven, my car is a Camaro weighing 3,lbs with driver, transmitting through a Tremec TKX 5spd manual, 3. Lunati recommends lbs seat and lbs over for valve springs Approx.

Probably it will, but there is more to it. The duration numbers and what type of induction will also be factors. I have a Pontiac I am not a drag racer. However, I enjoy more mid- to upper-range power. I am running a FAST 2. What would be my narrowest lobe-separation angle to achieve 10in of vacuum? Having only 7. Often, street cars have vacuum hoses connected to numerous accessories, even the heater box.

Without knowing the cam duration at 0. Camshaft duration is the measurement of the time one valve begins to open until it finishes closing, and it is measured in degrees of crankshaft rotation, not camshaft rotation.

If it is degrees 0. But if you have a large camshaft with LSA, it might generate the little vacuum you describe. Compare two camshafts, one with degrees 0. If your fuel injection system is satisfactory and the engine functions well enough, it may not be in your interest to change the camshaft. But with insufficient vacuum, some EFI systems are inadequate. If it is port injection with the injectors located on each port down by the valve covers, the fuel distribution will be acceptable.

The most intractable problem occurs with throttle body injection systems, blowing raw fuel where the carburetor would be. That said, the Holley Sniper appears to be a completely other creature.

From our consensus, the reflections of half a dozen leading engine builders, it is superior to all others of this kind. One final point, most of the time enthusiasts are not at fully open throttle, unless during track racing or in a boat. Few of us exceed 3, or 3,rpm in street cars. Thus, it is almost irrelevant whether your engine generates or hp.

Generally, when you increase camshaft size, it harms power output in this range. I have a Chevrolet powered by a small block. The truck came with an Engine Pro camshaft MC It is a heavy lobe cam with an LSA of degrees, Lash is 0.

Will the Holley Sniper compensate for the cam or should I add something to boost the vacuum pressure? Theodore, Increasing numbers of engine builders will tell you that it might work but perhaps not. Entry-level EFIs please forgive if this an impertinent term can be troublesome with low vacuum at idle. Your present camshaft would likely perform better with a throttle body with port injectors situated down near the valve covers.

On the other hand, if you wished to retain your EFI you may be obliged to change your camshaft — to decrease its specs. My question is this, should I have selected a LSA instead? Have I chosen the right cam to facilitate a good-running engine?

Please help. Given your engine size, your selection of lobe separation angle is probably fine, and with what seems like Cup Car specifications, the engine will sound impressive. I may try a 2 degree advance.

What do you think? I have a roller cam that was ground based on the CS XSSm with a baseline rpm of to rpm. This is a dirt track racing engine and my roller is pulling 19in of vacuum at 1,rpm. The cam is with lobe separation angle and. On engines equipped with independent intake and exhaust cams, the LSA is adjustable. It is possible to advance and retard the timing events, but the distance between the centerline of the lobes will remain constant.

Now that we have a basic understanding of lobe separation angle, we can put together a test to illustrate just what happens when you make changes to it.

Before getting to the cam profiles, we had to make sure we had a reasonable test engine. The standard bore block was then stuffed with a forged steel 4.

To illustrate the differences offered by changes in the LSA, we had Crane cams grind us three cam profiles that shared the same lift and duration figures, but differed only in the LSA. The custom cams we selected all featured 0.

The first cam featured a wide degree LSA, while cam number two narrowed the angle to degrees. The final cam was tighter still, with a degree LSA. Equipped with the degree LSA cam, the hybrid stroker produced hp at 6, rpm and lb-ft of torque at 5, rpm. Another important measurement was the torque production at 4, rpm and this cam checked in with lb-ft of torque.

Next up was the degree cam, which actually lost out in peak power slightly to the degree cam, but offered considerably more torque. The degree cam produced peak numbers of hp at 6, rpm and lb-ft of torque while pumping out lb-ft of torque at 4, rpm.

The final, degree cam stepped power up even further, with peaks of hp at 6, rpm and lb-ft at 5, rpm. This cam also offered the highest torque output at 4, rpm with lb-ft.