GM Vortec Heads
We got our Vortec Heads from a shop in Abernathy, Texas. They are manufactured by GM and are standard equipment on 1996 and newer trucks. They feature 1.94/1.50 stainless steel valves and 64cc cumbustion chambers, which yeild approximately 10:1 compression with a stock height engine deck and flat top pistons. The heart shape of the combustion chambers cause an excellent fast burning swirl pattern of the air/fuel mixture. They flow well for performance up to 6500 RPM. These heads are an awesome choice for anybody who is building a small block Chevy who want's great street/strip performance without breaking the bank. Using these heads requires some signifigant planning however, as they are different from the types of heads that most of us are fimiliar with. They are not all out race heads, but they can be "tuned up" significantly with a little bit of forethought.
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A Vortec head
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Ports of a Vortec intake compared with traditional ports
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The combustion chambers of the Vortecs
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Screw in studs and guide plates
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A Vortec valve cover
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Torquing down the heads
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Improving Flow
By removing an exhaust valve from these heads, you can find a small ridge just under the valve seat which covers about 180 degrees of the port. By smoothing these ridges with a die grinder, you can increase the flow of these heads to about 85%. We pulled our heads apart and Tom ground the metal, taking careful precaustions to aviod any debris entering the valve guides. To ensure cleanliness, he bought and used a set of barrell brushes.
CAUTION: It is extremely easy to screw up a valve seat with a die grinder while grinding the ridge out of the exhaust port. Please be extremely careful!
Valve Springs
The springs in these heads are good up to about .450 lift, however if you are planning on using these heads on a high performance engine, you should probably get aftermarket springs. We got a set from comp cams that will work fine with our .480 lift cam.
Rocker Arms
Tom and I decided that roller tip rockers would be the way to go with our engine, as we were advised that they provide a significant performance increase for the money. We did not realize at the time that the Vortec heads use self aligning rocker arms. These are rocker arms with small ridges on the pushrod end which keep the pushrods straight. There are no pushrod guides built into Vortec heads. What's worse, at the time we built the engine, nobody was making self-aligning roller tip rockers. You could only get the O.E. style stamped rockers or full roller rockers in self-aligning styles. Because the advantages of full roller rockers are negligable below 6500 RPM, we decided the added expense was unnecessary. We instead had the original push in studs removed, and had the heads machined for screw in studs with guide plates. Guide plates for the pushrods eliminate the need for self-aligning rockers.
Valve Covers
The vavle covers for Vortecs are a different style than previous small block Chevy heads. They accept four bolts right on top instead of the traditional two on each side. They are rediculously priced in the major catalogues and retailers, so we hunted around 'till we found a pair at a junkyard. They we all chewed up on the underside where braces had apparenly once been mounted. We found that the missing metal brackets were designed to keep you from tightening the covers down too tight. Instead of worrying about this technicality, we were just really careful while tightening the bolts. Finding the screws for the valve covers was a whole different ordeal which involved a covert search and rescue mission at the local Chevy dealership.
Tom recently found a new pair of valve covers for us at only half the price of the first. Better yet, the bracing is still intact.
Intake Manifolds
The Vortec heads have a revised intake port design. Instead of being an ovaled-rectangle, they are tapered towards the top. They do not line up with non-Vortec intake manifolds, and neither do the bolts which hold the intake on. The easiest way to go is to buy a manifold such as the Edelbrock Performer Vortec or Performer RPM Vortec, which fit perfectly. Although we've heard that you can drill the heads out for standard manifolds, this method seems rather unhealthy because of the misaligned intake ports.
See the engine page for more information and pictures related to vortec heads.
