Increased power for your 1996 to 2000 350ci Chevy Vortec 5700 V-8 enginePosted in How To: Engine on July 12, 2016 0) (
GM LS V-8 engine swaps seem to be all the rage, and for good reason. They deliver a lot of power and efficiency with little effort. However, that doesn’t mean you should toss out your perfectly running cast-iron Vortec 5.7L like old bathwater. The ’96-’00 350ci Vortec 5700 engines enjoy lots of aftermarket support to help improve the 255 hp and 330 lb-ft of torque they’re rated for at the crank. An engine swap can be quite costly, so putting even a quarter of those funds into your Vortec 350 engine could get you where you want to be.
When it comes to making cheap and easy power with almost any V-8, it’s hard to beat a camshaft swap. So, that’s what we set about doing with our 65,000-mile ’96 5.7L Vortec engine. Once we finished the installation, which included a hydraulic roller Crane Cams camshaft and valvetrain bits, along with Taylor Cable throttle body and intake spacers, we sent the truck out to The Dyno Shop in Santee, California, to have the computer tuned. Some tweaking on the dyno resulted in a much better air/fuel ratio and almost 20 hp on top of the 45 hp we gained from the cam swap.
Unfortunately, we were unable to get a baseline on the dyno before the cam swap. However, you can generally figure on about a 20 percent loss of power through the drivetrain. For our application, 20 percent is a bit conservative given the Ford 9-inch rear, tight gearing, and bigger tires, but that’s what we’ll go with to be conservative. That 20 percent reduction would have put our stock 255hp 5.7L at around 200 hp at the rear wheels. The cam swap bumped us up to 245 hp, and with the computer tuning, we hit 268 hp. But what is more impressive is the incredibly flat torque curve that hovers around 280 lb-ft all the way up to 5,000 rpm, which makes this a great engine for towing, dirt abuse, and daily driving. Our engine is backed with a stock 4L60E four-speed automatic and 5.29 axle gears. Our truck rolls on 37-inch tires and weighs 5,400 pounds. We noticed an immediate improvement in on-road drivability. Overdrive used to be kind of sluggish. Now the transmission feels like an actual four-speed. The truck is more fun to drive and much quicker. Throttle response is noticeably crisper, and we don’t feel like we have to floor it as often to get where we are going.
Our engine started as a stock L31 with 65,000 miles on it. We had added a custom intake tube that runs to dual UMP filters because this truck sees extra-dusty conditions on a regular basis. It’s possible our gains may have been a little higher with a simple off-the-shelf cold-air intake tube with an oil-impregnated gauze filter, but none can touch the filtering protection of the UMPs.
We started by rotating the crank to top dead center and disassembling the engine. You can install a new camshaft with the engine still in the vehicle in most cases. You’ll need to remove the radiator, intake, part of the front accessory group, water pump, timing cover, valve covers, rockers, pushrods, lifters, and so on. Since we were already most of the way in there, we eventually decided to pull the engine and replace some leaking seals that had been bothering us.
With the all of the other components out of the way, you can remove the camshaft from the engine block. Be careful when pulling it out—you don’t want to nick or damage the cam bearing surfaces inside the block with the sharp edges of the camshaft lobes.
Our Crane Cams cam (PN08-500-8) has a duration of 206/212 at 0.050 and lift of 0.480/0.488 ground on a 112 lobe separation angle. It’s a great torque producer and pulls a lot of vacuum at idle to keep the computer system happy. We lubed each lobe of the new cam with assembly lube before carefully sliding it into its new home.
Our old timing chain and gears were in good shape. We lined up the timing marks and reinstalled the parts. If your chain or gears look at all worn, now is a good time to replace them.
A cam swap does not require the removal of the heads, but we had some leaks to fix. Since the heads were already off, we gasket-matched the intake and exhaust ports with a die grinder just to take care of any small misstep between the intake and head transition. Don’t go too deep if you don’t understand head port flow characteristics or you could actually reduce the intake charge velocity and hurt performance. Many aftermarket companies offer fully ported small-block Vortec heads if you’re working up a high-performance application.
We added a Taylor VMAX manifold spacer kit to our 5.7L. The spacer is said to increase air volume by up to 31 percent, which should help improve throttle response, torque, and horsepower. The beautifully machined, 1-inch-thick billet-aluminum spacer is O-ringed just like the stock intake manifold, making it easy to install.
We reinstalled our home-job ported heads and slapped Crane Cams OE replacement lifters (PN 850-16) into the block. The heads received Crane Cams beehive springs (PN 26918-16), which allows clearance of the stock valve guides while achieving a max lift of .500-inch. The springs and valves are clipped in place with Crane Cams steel spring retainers (PN 787-16). Crane Cams Magnum 1.52:1 roller rockers (PN 1417-16) free up some extra horsepower by virtue of their lower friction. We could have gone with 1.6:1 ratio rockers to eke a bit more lift (and power) out of our camshaft, but that would put our net lift at 0.505-inch, right at the ragged edge of the valvesprings’ bind limit without machining the valve spring seat and guide.
We had already welded an aluminum ring to the top of our throttle body to attach our air cleaner assembly. The narrower section of the stock throttle body was bored out on a lathe. The large diameter is unchanged, and we still have the stock butterfly. We added a Taylor throttle-body spacer, which is said to improve throttle response and increase torque and horsepower.
Even though hydraulic roller camshafts don’t require the extensive break-in procedures of a flat-tappet camshaft, we still took the precaution of filling our engine with Maxima Performance Break-In oil to make sure the cam wasn’t damaged during the first run. This oil has extra additives that reduce the wear on internal components.
The Dyno Shop found that our combination of parts caused our engine to run too lean. Reprogramming the computer, correcting the air/fuel ratio, and advancing the timing 2 degrees resulted in an increase of almost 20 hp at the wheels over the cam swap alone. We’re still using the stock injectors and fuel pressure regulator.
We estimate that we started with about 200 hp at the rear wheels and discovered the cam and tuning bumped us up just over 68 hp and creates a very flat torque curve, which hovers around 280 lb-ft all the way up to 5,000 rpm. This chart shows the before and after tuning of the computer by The Dyno Shop.