Chevrolet Performance Parts

     GM SBC 350 CI Vortec L31 Heads and compatible parts for the Vortec Heads.
     This production Vortec iron cylinder head was first used on the 1996 pickup truck RPO L31 with fuel injection. America’s favorite high performance cast iron small block cylinder head offers big power and bigger value.
     Keys - gmhead, gmheadpart

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CYLINDER HEAD NAVIGATION

GM Cylinder Head Index	GM 4 & 6 Cylinder Heads	GM Small-Block Heads	GM Big-Block Heads
GM Cylinder Head Parts	GMPP SB Reference Chart	GMPP BB Reference Chart	GM L31 350 Vortec Head
GM Fast Burn 350 Heads	GM 350 Swirl Port Head

GMPP CAST IRON VORTEC HEAD ASSEMBLY

P/N 12558060 L31 350 Vortec Cylinder Heads (See options below.)

Small block Vortec heads, the head with huge performance gains that everyone is talking about.
This production Vortec iron cylinder head was first used on the 1996 pickup truck RPO L31 with fuel injection. The intake and exhaust port are very similar to Corvette 350 LT1 heads. America’s favorite high performance cast iron small block cylinder head offers big power and bigger value. The Vortec cylinder head's fast burn combustion chamber and high velocity ports combine to produce big horsepower out of the box. The Vortec head can be mildly ported for additional performance and can be milled up to .040” for increased compression ratio. This head includes 1.94” intake valves and 1.50” exhaust valves, springs and retainers, and pressed-in 3/8” studs. This head with compatible valves flows more air than bow tie head P/N 10134392, but the casting may not be as durable. It is a 20 to 40 horsepower bolt on increase over earlier cast iron small block heads. The water passages are the same as the original 1955 small block design. The eight-holt intake bolt pattern is totally different than the early model V8 12-bolt design. The Vortec head REQUIRES a Vortec style intake manifold due to its improved manifold mounting flange and gasket design and raised intake ports. It is not recommended that the heads be modified to accept early design intake manifolds (They will never match up right.). Use new manifold P/N 12366573, 12496820, 12496821, 12496822, or any others that we have listed below for correct matching to the Vortec head. Vortec heads fit all small block engines produced 1955 to present, excluding LT1/LT4 reverse coolant flow engines and current LS1 style “GEN 3” engines. Technical Note: The valves seats in these heads can be machined to 2.02” intake and 1.60” exhaust. The rocker arm studs can be pinned or drilled and tapped 3/8”. These heads require the use of self-aligning rocker arms. (Casting P/N 10239906 or 12558062) (65 ft./lbs. head bolt torque) Please Note: The casting number myth debunked: The myth is that there is a difference in the head performance produced by these two castings. This myth was started by some Magazines that didn't do their homework before publishing their articles. This is the truth the whole truth and nothing but the truth. So sayith the Grand Wizard GM and his Apprentice Wizard Chevrolet. 10239906 casting has one large single hump. 12558062 casting has 3 small humps. If either of these two castings have not been altered by GM and the part number changed from 12558060 or altered by someone else (previous owner, etc.), the heads produced by either casting will be identical except for the external cosmetic difference. Both castings are used to make the 12558060 Vortec heads which are the true unaltered Vortec heads. Heads from both castings come out of their cast IDENTICAL except for the minor cosmetic external differences!!!!!!!!

VORTEC CYLINDER HEAD TECHNICAL INFORMATION

Part Number: 12558060
Description: L31 with valves
Material: Cast Iron
Head Bolt Torque: 65 ft./lbs.
Valvespring Seat: 1.300” O.D., 0.850” I.D.
Valve-guide Seals: Viton rubber positive seals, total 0.450” retainer-to-seal clearance

Combustion Chamber Volume: 64 cc
Spark Plugs: Straight
Heat Risers: No
Valvesprings: Single wire with damper 1.235” O.D., 0.875” I.D. 75-pound seat pressure @ 1.700” installed height Coil-bind @ 1.150”
Intake Bolt Pattern: Four bolts per side
Rocker Arm Style: Self-Aligning

Intake Runner Volume: 170 cc
Valve Diameter: I: 1.94”, E: 1.50”
Casting Numbers: 10239906 and 12558062
Max. Valve Lift: 0.420” which allows 0.030” retainer-to-seal
Rocker Stud: Press-in, 3/8” diameter
Spark-plug Style: 14 mm, ¾ reach, tapered seat

Notes: LT1 Design Port with valves and springs.

Click here for a comparison chart of intake and exhaust flows.

Click here for a slightly bigger picture of a Vortec head.

VORTEC HEAD OPTIONS

Special Intake Manifolds For The Vortec Heads
P/N	Option
2116	Edelbrock Performer
21161	Edelbrock Performer, Polished 2116
5426	Edelbrock C-26 Dual-Quad (Page)
7116	Edelbrock Performer RPM
71161	Edelbrock Performer RPM, Polished 71161
2913	Edelbrock Super Victor, Single-Plane
2912	Edelbrock Victor JR. Sportsman 2V Vortec
7516	Edelbrock Performer RPM Air-Gap Vortec (Page)
75161	Edelbrock Performer RPM Air-Gap Vortec, Polished 7516
12496820	GM EGR Style, For Dual Pattern Style Carb’s
12366573	GM RPM Style, Square Pattern Carb.
12496821	GM TBI With EGR (Page)
12496822	GM Eliminator Vortec Design (Same as Edelbrock P/N 2913)
------	Holley MPI Commander 950, MPFI Fuel Injection Kits. Click on Page link for P/N’s and description.(Page)
3507	Edelbrock Performer RPM Pro-Flo® EFI NEW!.
Note: You can view a page with pictures and descriptions of the Edelbrock Intakes mentioned above.
Special Rocker Arms For The Vortec Heads
12495490	GM Rocker Arms, 1.5 Ratio, Stamped Steel, Self-Aligning Style
12370838	GM Aluminum Roller Rocker, 1.5 Ratio, Self-Aligning
12370839	GM Aluminum Roller Rocker, 1.6 Ratio, Self-Aligning
1417-16	Comp Cams Magnum Roller Rocker, 1.52, Roller Tip, Self-Aligning
1418-16	Comp Cams Magnum Roller Rocker, 1.6, Roller Tip, Self-Aligning
1317-16	Comp Cams Pro Magnum Roller Rocker, 1.52 Ratio, Self-Aligning
1318-16	Comp Cams Pro Magnum Roller Rocker, 1.6 Ratio, Self-Aligning
10751-16	Crane Gold Roller Rocker, 1.5 Ratio, Self-Aligning
10758-16	Crane Gold Roller Rocker, 1.6 Ratio, Self-Aligning
Special Camshafts For The Vortec Heads
We can supply many grinds to meet you application needs. Example: 12-235-2 Comp Cam Extreme 4 X 4, flat tappet cam, lift I .447”, E .462”, duration @ .050” 210 I, 218 E. Strong low end and mid range torque. Excellent cam for R.V., and pickups when changing to the Vortec heads. Note: Valve spring change is required with this cam.
Special Valve Covers For The Vortec Heads
12355350	GM Chrome With Red Bow Tie In Center
SCTZVC	New “Take Off” ZZ-4 Black Valve Covers (When Available)
24502540	Valve Cover Adapter, Converts Center Bolt To Outside Bolt
10046089	Center Bolt Valve Cover Gaskets (price is for one gasket)
241-75	Holley Custom, Cast Aluminum, Ball-Milled Top, Valve Covers. The rigid 1-pc aluminum castings combine strength and light weight in a design that provides a tight gasket seal while also acting to reduce valve train noise. (Pic)
241-74	Holley Custom, Cast Aluminum, Polished Flat Top, Valve Covers. The rigid 1-pc aluminum castings combine strength and light weight in a design that provides a tight gasket seal while also acting to reduce valve train noise. (Pic)
9415	MR Gasket, 87 & up SBC , center hold down, baffled. (2 covers, 1 oil fill cap, 2 PCV/breather grommets.) (pic)
Special Valve Springs For The Vortec Heads
10309-1	Crane Cams valve spring and retainer kit. (drop-in springs with no machine work needed)
Labor to set installed height and assemble springs and retainers. $40.00
Special Head Gaskets For The Vortec Heads
10105117	GM Composition Head Gasket, .028” thick compressed. (price is for one gasket)
12557236	GM Composition Head Gasket, .051” thick compressed. (price is for one gasket)
1094	Fel-Pro Head Gasket, .015” thick compressed. (price is for one gasket)
Special Intake Gaskets For The Vortec Heads
89017465	GM Intake Gasket. [Old P/N 12529094]
1255	Fel-Pro Intake Gasket.
Special Spark Plugs For The Vortec Heads
5613611	R44LTS, set of 8
5614210	MR43LTS, set of 8
25164641	#3, rapid fire style, set of 8
P526S	Accel U-Groove “SHORTY” Double Platinum Header Plugs approximately 3/16" shorter then R44LTS plugs, set of 8 (Pic)
Special Misc. Parts For The Vortec Heads
12495499	GM Head Bolt Kit
12495491	GM Flat Tappet HD Push Rod Kit
12371041	Factory Roller Cam Push Rod Kit
12550027	GM Intake Bolts Set
134-2002	ARP SBC Vortec, Intake Bolt kit. 8 6-Point Bolts and 8 Washers, Black Onix. (Price Key -ARP)
434-2002	ARP SBC Vortec, Intake Bolt kit. 8 6-Point Bolts and 8 Washers, Stainless Steel. (Price Key -ARP)
134-2103	ARP SBC Vortec, Intake Bolt kit. 8 12-Point Bolts and 8 Washers, Black Onix. (Price Key -ARP)
434-2102	ARP SBC Vortec, Intake Bolt kit. 8 12-Point Bolts and 8 Washers, Stainless Steel. (Price Key -ARP)
8032	Edelbrock Universal Throttle Bracket. For SBC Vortec or Edelbrock E-Tec. (Price Key - Use P/N Please.) (Pic)
Bare Vortec Head
12529093	Same as P/N 12558060 except it doesn’t include intake valves, springs, and retainers.

CHEVY HIGH PERFORMANCE MAGAZINE ARTICLE ON THE L31 VORTEC HEAD

From Chevy High Performance Magazine
Iron Vortec Head
All the Details You Need to Know
By Jeff Smith
Photography: Ed Taylor, Jeff Smith
     We’ve been getting a ton of mail with questions about how and when to modify the Vortec small-block iron heads - so much mail that we decided to condense all the Vortec information into one concise story that should answer almost any question you have about this powerful iron cylinder head.
The Early Days
     In 1996, GM incorporated the port design from the very successful iron LT1 engines used in the Impala SS, which was improved over the aluminum LT1 Corvette and Camaro engines. In essence, the Vortec head uses the iron LT1 chamber intake and exhaust ports in a standard-water-flow iron head. These production Vortec heads were used in the new Vortec 350ci engine intended for ½-, ¾-, and 1-ton Chevy pickups. Amazingly, this mundane, production-based 1.94/1.50-inch valve head performed better than the iron Bow Tie head. The deal of century occurred when GM Performance Parts decided to sell these heads as complete units for under $500 per pair, ready to bolt on. For you junkyard hunters, be forewarned that some ¾- and 1-ton trucks came with Vortec heads equipped with a specially hardened exhaust seat that kills low- and mid-lift flow. Casting number 10239906 should be avoided.
     Chevy enthusiasts quickly discovered that these heads are capable of 400 hp right out of the box when teamed with a performance intake and a camshaft. But there are several changes that must be made before bolting this head onto your engine. We’ll run through all of them here and offer a few recommendations based on our experience.
Bolts, Springs, and Such
     There are several important requirements dictated by the use of the Vortec head. The most important detail is that the Vortec uses an eight-bolt intake-manifold pattern that is different from the standard 12-bolt pattern. The Vortec requires a specific Vortec intake manifold available from both GM Performance Parts and Edelbrock. On dozens of dyno-tests, we have had the most success with Edelbrock’s Performer RPM and the RPM Air Gap models. Professional Products also offers a specific Vortec intake. The intake ports are also significantly taller than typical small-block ports. While companies such as Jim Pace offer modified heads that will accept a standard 12-bolt intake, this requires a manifold with at least a 0.325-inch-tall sealing surface above the top of the intake port.
Inserted by Chevrolet
     Do not try to modify either the heads or the intake manifold to try to make the Vortec heads match up to a standard 12-bolt intake manifold. The ports will not match up. You must use a Vortec style intake manifold with any Vortec style cylinder head.
     Most street intakes require welding and machining to create the proper sealing area. This is both expensive and time-consuming. Using a dedicated Vortec manifold is the best choice and probably less expensive.
     The Vortec head also requires the use of center-bolt valve covers, and the good news is there are several styles to choose from. If you decide to use Corvette-style covers, you will have to trim the driprails inside the covers with a die grinder if you opt for roller rockers. Crane offers narrow-body rocker arms designed to work with center-bolt valve covers, but these are more expensive than standard roller rockers. Stock Vortec heads come with pressed-in 3/8-inch rocker studs and do not use guideplates. The rocker arms are guided (also called “rail” rockers) and employ a pair of guides or rails that center the rocker arm over the valve. This eliminates the need for pushrod guideplates. GM Performance Parts, Crane, and Comp offer self-aligning stamped-steel and roller-rocker arms that will bolt right on. Or, you can modify the heads to add screw-in studs and guideplates and then use conventional rocker arms, but be forewarned that this can add over $200 to the cost of the heads. Do not use guided or self-aligning rocker arms with heads that use guideplates, since this will cause pushrod bind and excessive wear. Also be aware that 1.6 rockers move the pushrod very close to the pushrod hole. Elongating the pushrod hole should be considered essential when using 1.6 rockers.
     This leads us to valvesprings, which require the most attention in a performance application. Since this is an OEM iron head, GM designed the valve guide to also serve as the inside diameter (id) locating device for the valvesprings. The guide’s large diameter acts like a sleeve that keeps the single-wire valvespring located properly. The guide is also machined at the top to mount a positive-style, 0.560-inch-diameter valve-guide seal. All of this conspires to limit total valve lift to a safe figure between 0.420 and 0.430 inch. The limitation is the clearance between the bottom of the retainer and the top of the valve-guide seal.
     Accommodating more valve lift requires modifications to the valvespring seat and valve-guide areas of the head. The best route is to increase the spring-seat diameter from the standard 1.25 inches to 1.440 inches. Both Comp and Crane offer tools that use a valve-guide arbor to position the cutter. The Comp Cams cutter increases the spring-seat diameter while simultaneously reducing the outside diameter (od) of the guide boss. The Crane tool also cuts the valve-guide-seal diameter at the same time. Comp sells a separate tool that cuts a new guide seal and reduces the guide height to create additional retainer-to-seal clearance. Both cutters machine the top of the guide down to a 0.530-inch diameter, which is the standard size for positive-type aftermarket seals. This requires purchasing new valve-guide seals, since the factory uses a 0.560-inch guide to locate the seals. Another way to go is to have a machine shop cut the guide boss diameter to around 0.760 inch and reduce the seal height and use either the Crane H-11 tool steel spring (PN 99846) or the Comp spring (PN 981).
     Once these machining operations have been completed, you have the choice of several aftermarket valvesprings to match your cam profile. These machining operations will produce enough clearance to allow between 0.525- and 0.550-inch valve lift before running into valvespring coil-bind. Given a 1.440-inch valvespring seat diameter, Comp and Crane offer several single and dual springs that will work with the stock valves.
Inserted by Chevrolet
     The Chevrolet solution is to use Crane Cam’s 10309-1 drop-in valve spring and retainer kit which is good for .550” lift with no machining.
     The installed height for this Crane Cams kit is taller and the lower part of the retainer is shorter.
     The “AVERAGE” clearance between the retainer and seal is .575” for this kit.
     We have found that some of the Vortec heads, coming from the factory, do not have the valve seals driven on all the way. You need to check that they are before installing this kit. If they need to be driven on all the way, we have found that a 3/8” drive - 1/2” socket fits the valve seal just about perfect.
     As with all modifications to performance engines though, you should always measure to assure that there is proper clearance and fit.

	The iron GM Performance Parts Vortec head has got to be the best deal in town.

	You can make 400 hp with a mild street 350 small-block using an unported set of these heads available complete for $480 a pair. Inserted by Chevrolet This was the price at the time this article was written and no longer applies.

	The Vortec heads come with a very efficient 64cc chamber using 1.94/1.50-inch valves. Despite the conservative valve sizes, these heads flow extremely well in the 0.300- and 0.400-inch valve-lift areas. Both the intake and exhaust valves incorporate a 30-degree back-cut.

	The stock springs will only accommodate around 0.420 inch of valve lift. Other limitations of the Vortec heads include the press-in rocker studs and the required use of center-bolt valve covers (arrow).

	The easiest way to identify a Vortec head is by the sawtooth pattern cast into the front. Look for casting number 12558062, but avoid casting number 10239906, which has a modified exhaust seat and loses 20 percent of its flow at 0.120-inch lift.

Inserted by Chevrolet There is no difference between either of the Vortec head (P/N 12558060) castings except for a couple of minor external cosmetic details. The two casting numbers are 10239906 and 12558062. GM has and does take some of the P/N 12558060 heads made from either of these castings and makes alterations to them to better fit specific applications. When GM does this, they change the part number of the head. Buying Vortec heads used is risky unless you know what vehicle they came out of, what part number the head is, and what modifications where made to the head to make it that part number. You can not go by the casting number, as suggested by this article, you have to go by the part number of the head when buying used Vortec heads.

	One area that can trip you up when selecting a performance valvespring is this large guide- boss diameter of 0.900 inch (arrow). Most performance valvesprings have a smaller inside diameter, which requires this boss to be machined down to about a 0.630-inch diameter.

	The Vortec head also uses guided rockers to position the rocker arm over the valve stem. If you choose not to run guided rockers, then you must add guideplates to the heads with screw-in studs.

	GM offers an excellent stock intake-manifold gasket that uses pins that precisely locate the gasket on the head. It requires no adhesive and uses silicone rubber seals around the ports. The Vortec head requires the late-model eight-bolt intake bolt pattern.

	The GM valve-guide seals (0.560-inch boss) are excellent items, but when the guides are machined, the valve-stem seal boss is generally cut to 0.530, which requires aftermarket seals.

	There are several center-bolt style valve covers available for the Vortec heads. You can even bolt on TPI-style magnesium covers, but these require minor machine work to clear roller rockers.

	Additional valve lift from a big cam and/or 1.6:1 rocker arms will require minor pushrod hole modifications to prevent bent pushrods. You can perform this modification yourself with a drill motor and a 1/2-inch bit. Be sure to drill at the pushrod angle. Comp sells a tool that helps position the drill bit properly.

	Using the Comp Cams tool with a handheld drill motor, we machined the valvespring seats out to 1.440 inches and reduced the guide diameter and the height with the second Comp tool. But even with better springs, you are limited to about 0.525-inch lift before you encounter coil bind. CHP

L31 VORTEC HEAD FLOW COMPARISON

	Intake Flow Comparison			Exhaust Flow Comparison
Valve Lift	GMPP Fast Burn	GM Vortec L31	GM Stock Iron 882	GMPP Fast Burn	GM Vortec L31	GM Stock Iron 882
0.050”	30	40	39	23	25	34
0.100”	61	70	70	53	48	58
0.200”	126	139	125	107	101	108
0.300”	180	190	175	140	121	135
0.400”	221	227	204	167	140	141
0.500”	243	239	205	178	147	142
0.600”	238	229	206	184	151	142
Note: Vortec L31 and Stock Iron 882 flow data where obtained from Car Craft Magazine’s Web site in their Technical Articles section. The Fast Burn (new version) flow data is Chevrolet’s data. These are not offical GM specs on these heads and we don’t beleive that GM has ever published specs on these heads or we would have used that instead.