426 Hemi Engine Intake and Exhaust Valves: The Factory Sizes

One of the components to 426 Hemi Engine is the size of its intake and exhaust valves.

The 426 Hemi intake valve head diameter is 2.25,” the length is 5.316″-5.331″ and the stem diameter is .3085″-.3095.” The exhaust valve head diameter is 1.94,” the length is 4.7543″-4.7693″ and the stem diameter is .3075″-.3085.” Both valves face angles are 45 degrees.

This article will take a closer look at the intake and exhaust valves specifications for all six years of the 426 Street Hemi Engine production. This will include the valve guides, springs and clearances.

426 Hemi Intake and Exhaust Valves

The 426 Hemi has 16 total valves, eight intake valves and 8 exhaust valves. There are two valves per cylinder.

There are some size and clearance differences between the two different types of valves. The table below contains all the specifications of each one.

Valve Specification	Intake Valve	Exhaust Valve
Number	8	8
Valve Head Diameter	2.25″	1.94″
Length (to center of Valve Face)	5.316″-5.331″	4.7543″-4.7693″
Stem Diameter	.3085″-.3095″	.3075″-.3085″
Stem to Guide Clearance Maximum Allowable	.002″-.004″ .017″ *	.003″-.005″ .017″ *
Face Angle	45°	45°

426 Hemi Intake Valve and Exhaust Valve Specifications – * With tools C-3973 and C-3339 using wobble method.

426 Hemi Valve Guides

The following is the intake and exhaust valve guide specifications:

Type: Cast in Head.
Valve Guide Bore Diameter: .3115″-.3125″

Cylinder Head Valve Specs

The following are the cylinder head valve specifications:

1966-1969 Cylinder Head

Valve Seat Runout (Maximum): .002″
Intake Valve Seat Angle: 45°
Intake Seat Width (Finish): .060″-.085″
Exhaust Valve Seat Angle: 45°
Exhaust Seat Width (Finish): .050″

1970-1971 Cylinder Head

Valve Seat Runout (Maximum): .002″
Intake Valve Seat Angle: 45°
Intake Seat Width (Finish): .060″-.080″
Exhaust Valve Seat Angle: 45°
Exhaust Seat Width (Finish): .050″-.070″

Valve Springs

The following are the valve spring specifications including the size, number and loads. The springs differ depending on which year more than any other specification.

In 1966 and 1967, the 426 Hemi had double valve springs. There were 32 valve springs, two outer and two inner springs per cylinder.

From 1968-1971, the Hemi had 16 valve springs.

426 Hemi valve springs. — 426 Hemi valve springs

1966-1967 Valve Spring Specs

Number: 32 valve springs
Free Length:
- Outer: 2.47″
- Inner: 2.20″
Load When Compressed to (valve closed)
- Outer (less surge damper): 102-108 @ 1-55/64″
- Inner: 47-53 @ 1-41/64″
Load When Compressed to (valve open)
- Outer (less surge damper): 179-189 @ 1-13/32″
- Inner: 86-96 @ 1-11/64″
Surge Damper: Outer only
Valve Springs I.D. Outer: 1.08″-1.010″
Maximum Allowable Out of Plumb: 1/16″
Valve Spring Installed Height (spring seat to retainer): 1-53/64″-1-57/64″

Use 1/16″ spacer to reduce spring height when over specifications.

1968-1969 Valve Spring Specs

Number: 16 valve springs (8 intake and 8 exhaust)
Free Length: 2.20″
Valve Springs I.D.: 1.070″-1.090″
Valve Spring Installed Height (spring seat to retainer): 1-53/64″-1-57/64″
Load When Compressed to (valve closed less surge damper): 110-120 @ 1-55/64″
Load When Compressed to (valve open less surge damper): 270-290 @ 1-3/8″
Maximum Allowable Out of Plumb: 1/16″”

Use 1/16″ spacer to reduce spring height when over specifications.

1970-1971 Valve Spring Specs

Number: 16 valve springs (8 intake and 8 exhaust)
Free Length: 2.15″
Valve Springs I.D.: 1.070″-1.090″
Valve Spring Installed Height (spring seat to retainer): 1-53/64″-1-57/64″
Load When Compressed to (valve closed less surge damper): 110-120 @ 1-55/64″
Load When Compressed to (valve open less surge damper): 300-320 @ 1-3/8″
Maximum Allowable Out of Plumb: .080″ (1970)
- 1/16″” (1971)

If you have any questions about the 426 Hemi Engine valves, send us an email found specifically on our contact page.

For the past 40 years, I’ve been studying and researching Mopar engines including the 426 Hemi. I installed my first Mopar heads/valves 38 years ago while building my first Mopar engine.