Chevrolet/GMC Gen III V8 Performance Mods

[Shaun_300]

Here's a few performance modifications for the new LS series V8s. The first "LS" engine ever produced was in late 1997, the "LS1" featured in Corvettes, Camaros, and Trans-Ams. It was an all aluminum engine that was light produced a pile of horsepower. GM did the smart thing in 1999, with the new body style C/K trucks, came along different variations of the LS engine in displacements of 4.8L, 5.3L and 6.0L. All the "old school" 5.0L and 5.7L Vortec chevy's were pretty much gone from the factory line up of vehicles. The 4.3L stayed (5.7L 350 with the 2 back cylinders cut off) and it still exists as an option even in 2010 2wd Silverado/Sierra work trucks. They now come standard with the 4.8L V8, but you can order them with the V6.

ANYWAYS! Enough history lessons for today, lets get to some horsepower! If you don't like horsepower, get the heck out of this room! (J/K )

First we'll start with the basics and cheap mods...

Take off your air filter cover and throw the original restrictive air filter in the garbage and put in a K&N air filter. This will flow way more air through the intake to feed your engine. The more air it can get in the better. It will give you better horsepower and fuel economy. If you want to go to a fancy looking one, get a K&N Cold air intake kit that has the pipe and cone style open air filter. I suggest not getting the one with the filter you have to oil, I've seen these screw up MAF sensors (Mass air flow) which will do all kinds of crazy things while you're driving lol. When it comes to the cold air intakes, opt for the plastic pipe, plastic does not hold as much heat as the nice chrome ones do. The cooler the air, the better!

Intake is very important to how your engine performs, but on the flip side of it, it's no good if it can suck lots of air in and not get it out! As for exhaust, you can get catylatic converter back exhaust setups like I have on my truck. They flow better and also give it a nicer sound with the performance muffler on it. Or if you want to go all out, get rid of all the stock exhaust and get some long tube headers, high flow cats, and run true duals. This is obviously the most expensive route, but it will give you the best performance.

These two mods alone will give you around 20 horsepower, along with better fuel economy.

Next step if that's not enough for you, is call Allan down in San Antonio, Texas. He is the owner of Nelson Performance, which is a big performance company that have dealt with tuning for Chevy trucks for years. I've heard nothing but good things about this company. I actually have a custom tuned PCM (Powertrain Control Module, the brains of a truck's engine and transmission) for my truck. He can adjust shift points and pressures, rev limiters, top speed limiters, and will play with timing and fuel curves to optimize your power out of your engine. I've heard of people gaining close to 40 horsepower with just a tune alone from Nelson Performance. Check them out!

Now I'll get into the more advanced modifications. They may sound complicated, but if you have any mechanical skill at all, you can do them. If you ever want to do these let me know and I can guide you through it, give you torque specifications, and whatever.

Camshafts:

From the factory GM isn't very aggressive with their cam profiles. Low lift, low duration and wide LSA's. First I'll explain what all this means, a camshaft is what opens your valves. The cam turns by the timing chain which is turned by the crankshaft, both the crank and cam have sprockets which the chain is attached to. The cam sprocket is exactly twice the size of the crank sprocket which makes it turn half the speed the crank turns. If your engine is running at 4000RPM the cam is turning 2000RPM. The cam is in the block (on GM V8's). It turns, there is a lifter that rides on the cam, a pushrod on the lifter that goes up through the cylinder head, and a rocker arm bolts to the head. The pushrod is on one side of the rocker arm and the valve is on the other. When the cam rotates and pushes everything up, the valve opens. You'll see a cam spec for example the cam I'm putting in my LS6. 220°/224° .575/.575 112LSA The red numbers are duration, which means how long the valve stays open, in degrees. The first number is the intake valve, second number is the exhaust valve. The blue numbers are lift, which means the valve opens 0.575". In this case both the intake and exhaust valves open the same amount. The green number is LSA which is Lobe Separation Angle. This is kind of hard to explain, it is basically the angle which the lobes are apart. The higher the LSA, the smoother the engine idle. Most stock LSA's are 116-118, giving it the nice smooth idle. Once you get lower the idle starts to get choppier. 112 Is pretty choppy, but if you hear some dragsters that'll barely stay idling, the cam is probably 107-108LSA.

You can change your camshaft to one with a better profile to suit your driving habits, they have street cams, towing cams, fuel economy cams, some good all around cams. If you're wondering what the idle will sound like, just punch in "silverado 112lsa" or 114lsa or whatever into youtube and there's lots of videos of idles and revs. You can pick whatever suits your taste! To change your camshaft you need to take all the front accessories off the engine (alternator, waterpump, crank pulley etc), remove the intake manifold, unbolt the exhaust manifolds and take the cylinder heads off (on LS engines). Only reason to take the heads off is so you can take the lifters out. They're not like the older ones where you can get them out with just taking the intake off. Then you need to remove the front timing cover, undo the cam sprocket, the chain will come off when you take the cam sprocket off. Then there's a plate with 4 bolts that holds the cam in. Then you can pull the cam out. It is a bit tricky if you haven't done this before, you need to be really careful not to damage the bearings. the cam comes out in sections, once all the journals come out, you have to pass all the journals through the next bearing, etc until it's out. Lube up the new cam really good, put it in carefully. These engines are simple to time, basically line the dot on the cam gear up with the crank gear. The dot on the cam will be down, crank will be up. Put it all back together. When you start it, you need to hold the revs at 2500RPM for 15 minutes to break the cam in.

We'll start with that, my fingers are sore.

Any questions or if you have mods that you're wondering about and want more info on, let me know.

[texastrophies]

I will admit I didn't read through all of that, mostly because I don't have anything it applies to. But I do have an "LS" engine. Mine has a "7" behind it and is a few years older than what is mentioned and quite a bit bigger.

Keep this up, as I was typing this I glanced down and read a little more of your post, I like it.

[Shaun_300]

I will admit I didn't read through all of that, mostly because I don't have anything it applies to. But I do have an "LS" engine. Mine has a "7" behind it and is a few years older than what is mentioned and quite a bit bigger.

Keep this up, as I was typing this I glanced down and read a little more of your post, I like it.

LS7 is a 7.0L found in the newer (06+) Corvette Z06's. 505hp 525lb ft of torque. I know there was an old LS6 that was either a 396 or 454. What was the LS7?

[texastrophies]

Both the old LS6 & LS7 are 454's. The 7 is a HP version of the LS6. Late 60's/early 70's vintage.

[redkneck]

Good info Shaun!!! Thanks.

[Strut10]

IIRC, the old LS-7 was never installed in any production vehicles. It was a GM crate motor available at dealers. It was 15 HP stronger than the LS-6 that was in the Chevelles and 'Vettes.

Now........ do you know what an LS-34 was?? Had a very heavily modded one in my old Impala.

[Shaun_300]

Is that the 409?

[Strut10]

Is that the 409?

Nope.

[Shaun_300]

Not too sure, that's before my time. Could be a 427, 396, 327......

[Strut10]

It was a 10.25:1 2-bolt 396 with the forged steel crank and oval ports.

Now my brother runs an LS-1 in his old Impala. I won't expect anyone (without cheating and Googling it or something) to know what that is.

[Shaun_300]

Nope, it's not like me to be a cheater. I know the sizes of most of the engines back then, but don't know what year they were in what car etc,

[texastrophies]

Isn't that the HP 350 that were in the late 60's vette's.

[Shaun_300]

I believe they only had the 327 and 396's in the 60's Corvettes, then in the later 60's the 427 came out as an option.

[Strut10]

Isn't that the HP 350 that were in the late 60's vette's.

Nope.

335 HP 427.

10.25:1 2-bolt, oval port and cast crank. Only used in 1969 Impalas and Caprices.

[Ethan Givan]

Ok quick question. I have never put a performance cam in a motor, only stock. If you put a very aggressive cam in a motor do you have to change anything with the timing or valves? Seems to me that since the valves are opening farther and at different intervals than the stock cam that it could cause some issues.

[Shaun_300]

Ethan, depending on the lift specs on your cam, usually you'll have to replace the valve springs to accommodate for the higher lift in the cam. If you go really crazy, you may also have to change the length of your pushrods. With my cam, my pushrods were good, but the springs were not. I got high lift springs from Lunati.