[jamis]

Here are the specs copied from GM. Vortec is just a trade name, there where more then one head configuration. The problem is you find a lot of different specs described as "vortec". Some are not GM specs, but aftermarket engines describing themselves as a “vortec” engine because they are using “vortec” heads.

The complete L31 engines part# 12530282 and 12530283 are both Vortec engines found in trucks. The 12530283 is the heavy duty version with 4 bolt main and different head configuration but both use the same cam.

Intake Lift- .414"
Exhaust Lift-.428"
Intake Duration @.050"- 191
Exhaust Duration @ .050-196
Lobe Centerline-111

These specs are for the the L31 which is the truck engine head configuration that is most commonly used for performance. . This is the same casting I’m using but I'm running aftermarket valves, springs, retainers bla.bla bla

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.