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Old 10-31-2012, 09:25 AM   #4
Devs93
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Heads: The Vortec heads are great heads, but there are not without their problems. The valve springs only support up to 0.450-0.470” lift camshafts depending on the sources you read. Since the Vortec engines use hydraulic roller cams, it would be silly not to upgrade the springs in order to take advantage of today’s high lift roller camshaft designs with lift in excess of 0.500”. Chevy High Performance has an article on upgrading your springs here: http://www.chevyhiperformance.com/te...ort/index.html. In this example, the valve seats are machined and larger springs are installed. Springs are also available that will increase your valve lift without machining the valve seats. Comp Cams Beehive 26915 or the Beehive 26918 springs can be used as direct replacements without machining the heads and will allow up to 0.550” lift. Contact Comp Cams or Crane Cams and ask them directly for which springs they’d recommend if you are unsure. Here’s another article on everything you wanted to know on Vortec heads: http://www.chevyhiperformance.com/ho...458/index.html. The ideal aftermarket head for the Vortec engine IMO is the Edelbrock Etec head. A serious performer for the money.

Camshaft: better than a TBI engine and it’s a roller camshaft, so it’s pretty good, right? Nope. If you want to make big power increases, you have to change the camshaft. This bottleneck is intertwined with the previous two bottlenecks. With more fuel and heads that support high lift, a 400+ hp engine is entirely possible. Again, the combination of parts selection is the key here. Installing a camshaft in a stock Vortec engine is not going to perform miracles, but will improve performance. Please read later in the thread on how to choose the right camshaft for your truck.


I want to add a supercharger to my engine. How do I do that and what are my choices?
First off, supercharger kits are mainly designed and calibrated for the stock engine. It will tolerate mild performance upgrades such as headers and low-restriction exhaust systems, but if you want to start changing cylinder heads and camshafts, you’re going to need to find someone to custom tune your engine or do it yourself. Be prepared to troubleshoot A LOT when adding a supercharger to your engine. It is not as easy as it seems, although the power gains (and particularly the torque gains) are outstanding and well worth the efforts. Depending on your power output, you may need to upgrade the transmission as well, so keep this in mind before investing in a supercharger kit.

TBI engines:
There are three quality manufacturers that I know of: Whipple Industries, Weiand, and ATI ProCharger. Each has their selling points. The Weiand emissions-legal kit is the least expensive at under $3000, but hood space is definitely an issue since the TB sits on top of the unit. There is also a super-cheap $1500 non-emissions kit available that uses a carb setup. Here is an article from someone who has done this to their 350 engine: http://www.thirdgen.org/weiand142install. Definitely needs a cowl induction hood and you may need to modify it to make room for the air filter. A shorter open element filter with K&N Xtreme filter lid may work, but since I don’t have one I wouldn’t know. It uses a 144 roots-style supercharger that adds between 25-30% additional hp/torque. The potential for more boost is possible, but it is limited by the enormous heat that is generated by the roots-style blower. The Whipple supercharger is popular because of its efficiency and low-RPM performance, adding 40-45% more power. Full boost is achieved at low RPMs making this an excellent choice for trucks that need to tow. The ATI ProCharger is the only centrifugal supercharger available from a major company. It is intercooled and therefore provides 8-9 pounds of boost (2-3 more than the Whipple supercharger). Power is improved by 65%, but it is mainly in the upper RPMS. Don’t count on this supercharger to improve your towing capacity significantly around town. On the highway, sure, but you won’t have the torque that the Whipple unit provided down low.

Vortec engines:
In addition to Whipple and ATI mentioned above, there is also Vortec Engineering and Powerdyne, both of which are centrifugal supercharger designs. These superchargers will add up to 50% more power.


Will roller rockers or higher ratio rockers improve power?
Yes and maybe. Roller rockers will reduce frictional parasitic losses on the valvetrain components to free up a few ponies. Higher ratio rockers have their applications: useful on stock cams to improve lift and therefore flow more air, maximize the airflow potential of aftermarket heads and camshafts. They also have their drawbacks: Stock TBI heads have low flow potential and using higher ratio rockers with an aftermarket camshaft may not improve power over the aftermarket camshaft alone since the maximum airflow of the heads have been reached; Vortec heads only allow valve lift up to 0.470” and installing higher ratio rockers may surpass the valve lift depending if you’re running the stock cam or not. With the stock cam, 1.6 ratio rockers are dangerously close to that upper limit, but still under. So how do I decide? Guess it depends on your engine combination and what your future upgrade plans are. Keep in mind that higher ratio rockers will increase the advertised duration of your cam. Comp Cams now has a new XFI series of camshafts designed to use their beehive springs and 1.6 ratio rockers. There are both hydraulic and hydraulic roller versions of the XFI cam. The advantage is that you precisely know the advertised duration of the camshaft with its higher lift potential.


How do I choose the right camshaft for my engine?
Oh man, probably the most common question on this forum and the one with the most answers. You can get really technical answers or very simple rule-of-thumb answers. The reason there are so many different answers (and camshafts for that matter) is because it highly depends on your engine and transmission combination and how you plan on using your truck (towing, racing, daily driver, etc.) Transmission? What does that have to do with it? Well first of all, you can choose slightly more duration with a standard transmission because you can essentially adjust the stall of the engine when starting out from a stop. Automatic transmissions don’t have that luxury and usually stall at about 1100-1300 RPM. If you choose a high duration cam with a narrow LSA (lobe separation angle) for a lopey powerful engine, you’ll gain hp up top, but lose torque down low. More importantly, installing a large duration cam in TBI engines with their torque-producing, low RPM cylinder heads is a major mismatch. The heads will not be able to support the power above 4000 RPM where the cam will be making its most power. The results = a dog of an engine down low and on the high end.

Here are my recommendations for cam choices based on the engine combo you have (all of which need custom chips or performance tuning to work properly and maintain fuel economy. This is required for ANY camshaft upgrade.)

TBI 5.7L with stock heads, stock or 2000 RPM stall torque converter: Duration at 0.050” lift 206/216 with LSA 112. The Crane cam 113904 is my top choice, but as long at you stick to intake duration under 206 degrees, you’ll have a safe computer-friendly cam with gobs of power 4500 RPM and lower. Good for towing and performance applications and good all-round choice. Power level maxes out at 280-300hp.

TBI 5.7L with after market heads, stock converter: Highest lift possible is the key here to take full advantage of your performance heads. My choice would be Comp’s 260 XFI hydraulic camshaft, 216/223, 0.499”/0.492” lift with 1.6 ratio rockers or the Comp Cams XE256H, 212/218, 0.479"/0.486" with 1.6 ratio rockers. Expected power levels will be around 320-345 hp. The Comp XE256H is a perfect cam swap for upgraded Vortec heads if you run 1.5 rockers (0.449"/0.456") that won't require any modifications to the valve springs.

TBI 5.7L with after market heads, 2500 RPM stall converter, 3.42 or higher rear end: Comp’s Xtreme Energy Computer Controlled XE262H with 1.6 rockers (218/224 at 0.050” lift, 0.510”/0.517”) or "XFI" 268 Hydraulic Flat Tappet Camshaft, 224/231, lift 0.520"/0.515" w/1.6 Rockers if you want to push it. You WILL need a higher stall converter with these cams. Dyno simulations of these combos produce 365+ hp at 5500 RPM. Yes, from a TBI. Tuning and proper fuel deliver is a must.

Vortec 5.7L engine without spring upgrade: Crane’s 109815, 204/214, 0.429”/0.452” lift.

Vortec 5.7L with spring upgrade: Comp cams Xtreme Energy Computer Controlled XR254HR (206/212, 0.480”/0.488”) or Comp cams Xtreme Energy Computer Controlled XR264HR (212/218, 0.488”/0.495” lift).

Vortec 5.7L with performance Vortec heads (i.e. Edelbrock 170 E-Tech heads with max valve lift of 0.575”) and fuel/induction system upgrades: Comp’s 260 or 268 XFI hydraulic roller series, 210/218 or 218/224 at 0.050” lift, 0.560”/0.555” or 0.570”/0.565” lift, LSA 113, 1.6 rockers. You could even go with 280 XFI cam with a 2500 stall torque converter. How does 400+ hp sound?
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