I’ve got a rebuilt 350 long block and I’m looking at different cylinder heads. A couple of friends have told me that the Vortec head is a little better than the stock heads I was going to use. I’ve never heard of the Vortec heads—what are they and are they better than my stock heads? I’ve heard these are just stock iron heads. Thanks

J.T.

For a short period of time between 1996 and 2000, Chevrolet outfitted their small block Chevy truck engines with a redesigned cylinder head, calling this the Vortec engine series which has carried over to references to the cylinder heads. The Vortec was a completely new head that will bolt directly to any small block block, but this head offers several subtle yet important differences.

Close up of sawtooth vasting on a chevy vortec cylinder head
Stock Vortec head are easily identified by this saw tooth casting pattern on the end of the head. Summit Racing’s aftermarket Vortec head uses an engraved Summit logo. (Image/Jeff Smith)

Key Differences Between Stock & Vortec Heads

The biggest change is the new intake manifold bolt pattern that requires a specific Vortec configured intake manifold because this 8 bolt intake manifold pattern is completely different from the traditional 12 bolt (6 per side) small block version.

So if you are considering using a set of Vortec heads, keep in mind that these heads will require a new intake manifold along with Vortec-specific intake manifold gaskets.

The main reason the Vortec remains a very popular conversion for mild street small blocks is because this head offers the best intake and exhaust port flow of any production small block head. That includes the old “double hump” 461 heads from the 1960s that some older hot rodders claim were pretty good. In their day they were, but the Vortec is far superior in airflow, chamber design, and combustion efficiency.

Comparing Combustion Chamber Size

There are other important aspects of the Vortec head that should be noted. The first is the combustion chamber size is 64cc, as opposed to most late model production iron heads that measure around 76cc.

You mentioned that you are rebuilding a 350ci small block. Assuming you will be using stock replacement, flat top piston with the four valve reliefs, the 64cc chamber will drastically improve the static compression ratio compared to 76cc heads.

We used the online Summit Racing compression ratio calculator to estimate your static compression ratio. Assuming a 4.030 inch bore, a 3.48 inch stroke, a 64cc chamber, four-relief pistons (about 6cc), with the piston about 0.010 inch below the deck, and a 0.041 inch compressed thickness head gasket, the compression ratio would be exactly 10.0:1 which, when combined with a mild camshaft, would work very well.

Other Factors to Think About

There are other considerations worth mentioning. If you were to find a used set of production iron Vortec heads, be aware that these often suffer from cracks so it is worth it to have them Magnafluxed to check for cracks.

Another item worth consideration is the OE heads were limited to allow no more than 0.450 inch valve lift because the stock valve guides are very tall and more valve lift from a high performance camshaft will push the bottom of the valve spring retainer into the seal and cause damage. This can be rectified with simple machine work, but that also drives up the cost of the conversion. Keep in mind that even a good set of used heads will likely require new guides, springs, seals and certainly a valve job.

All of this could drive the price of a rebuilt set of heads well past $900 to $1,000.

Aftermarket Vortec Cylinder Heads

The good news is that several companies now make an aftermarket version of the Vortec head.

Summit Racing offers a brand new Vortec cylinder head complete with new 1.94/1.50 inch valves that are completely assembled with valvesprings that can accommodate up to 0.490 inch of valve lift. The springs are also compatible with either a flat tappet or mild hydraulic roller camshaft.

The combustion chamber on the Summit Racing Vortec head is slightly larger at 67cc, which will slightly lower the compression ratio to 9.7:1 compared to the above calculation.

This is not a major issue and would certainly work very well with current 91 octane pump gas.

Spark Plugs, Valve Covers & Valvetrain

Another point worth emphasis is that Vortec heads require a different spark plug compared to the traditional small block Chevy iron head spark plug. When GM redesigned the Vortec head, they moved the spark plug further into the combustion chamber.

This required a spark plug with a longer thread reach.

Spark plug held near a cylinder head
The spark plug on the right is the traditional small-block plug with a short 0.460 inch thread reach. The plug on the left is an Autolite 0.708 inch long thread reach plug that is required for the Vortec cylinder head. This this same long-reach plug is also used in the late model LS engines. (Image/Jeff Smith)

The older, traditional small block plugs use a thread reach of 0.460 inch while the Vortec heads require a longer reach at 0.708 inch. The AC Delco part number for this Vortec head is an R44LTS. The engine will run poorly and not respond to tuning if the incorrect, shorter reach plugs are used.

Another difference worth mentioning is that the Vortec head also uses what is called a center-bolt valve cover where the retaining bolts are placed in the center of the valve cover as opposed to the perimeter as on traditional small block heads. So Vortec heads will also demand different valve covers and gaskets.

Another difference is that the Vortec heads do not use a traditional pushrod guide plate. The original small block Chevy also did not use guide plates but relied on a hole drilled into the head that “guided” the pushrod. The Vortec head uses a different, guided rocker arm with limiters on the valve side of the rocker arm that locate the rocker arm over the valve tip.

Underside of a pair of rocker arms
The rocker on the left is a stamped steel, guided rocker needed with Vortec heads. Note the bumps or guides that straddle the valve tip which center the rocker on the valve. The rocker on the right is a traditional small block stamped steel rocker without the guides. (Image/Jeff Smith)

The production Vortec head used guided, stamped steel rockers that work well on mild performance engines but you can also upgrade to guided roller rockers if you choose. We’ve listed a Part Number for the Melling stamped steel rockers which are affordable and will work fine with a mild camshaft.

***

If you add up all the parts necessary for a Vortec conversion with new heads, the price could easily climb over four digits. But the advantage to running the Vortec heads is that a 355ci small block with a mild cam of around 215 to 218 degrees at 0.050 duration and lift of around 0.460 to 0.480 inch the engine should easily make 425 hp or more.

Chevy Vortec Cylinder Head Upgrade Parts List

  • Summit Racing Iron Vortec head, 67cc chamber – SUM-151124
  • Summit Racing Vortec dual plane aluminum intake – SUM-226019
  • Summit Racing Vortec dual plane aluminum intake – SUM-226062
  • Fel-Pro intake gasket – FEL-1255
  • Fel-Pro valve cover gaskets, center bolt style – FEL-VS50088R
  • Melling guided 1.5:1 stamped rocker arm (need 16) – MEL-MRK651
  • AC Delco spark plug for Vortec heads – ADO-R44LTS
  • Summit Racing replacement center-bolt valve cover – SUM-G3319B
  • ARP intake manifold bolts for Vortec heads – ARP-134-2002
Keywords
Ask Away!, cylinder heads, Vortec, vortec cylinder heads
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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.