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Positive Valve Sealing for Performance Engine Builds
COMP Cams 520-1 is a single metal-body Viton valve stem seal sized for a 5/16-inch valve stem and a .530-inch valve guide. Its compact .575-inch outside diameter helps preserve spring clearance while the Viton sealing element controls oil at the valve guide in compatible cylinder-head assemblies.
Key Features
- Metal-body positive-style seal for secure guide retention.
- Viton sealing material suited to performance engine operating temperatures.
- Designed for a 5/16-inch valve stem and .530-inch valve-guide diameter.
- .575-inch outside diameter supports valve-spring clearance in compatible assemblies.
- Sold individually for precise replacement quantities.
Fitment
| Application | Requirement |
|---|---|
| Universal dimensional fit | 5/16-inch valve stem with .530-inch outside-diameter valve guide |
| Compatibility check | Verify guide machining, retainer-to-seal clearance, spring inside diameter, and valve lift before installation |
Specifications
| Detail | Value |
|---|---|
| Manufacturer part number | 520-1 |
| Product type | Positive valve stem oil seal |
| Valve stem diameter | 5/16 inch |
| Valve guide diameter | .530 inch |
| Seal outside diameter | .575 inch |
| Seal material | Viton |
| Body style | Metal body |
| Quantity | One |
| UPC | 036584151739 |
What's Included
- One COMP Cams metal-body Viton valve stem seal
About COMP Cams
COMP Cams develops valvetrain components for street and competition engines, including camshafts, valve springs, rocker arms, pushrods, and precision hardware. Its valve-seal range is organized by verified stem and guide dimensions for accurate component selection.
Related Parts
- No related product is linked because valve springs, retainers, locks, and guides must be selected from verified cylinder-head dimensions rather than general similarity.
FAQ
What is the 520-1?It is one metal-body Viton positive valve stem seal for a 5/16-inch valve stem and a .530-inch valve guide.
Is this seal sold individually?Yes. The package quantity is one seal, so order the quantity required for the number of valves being serviced.
What valve stem size does it fit?It is designed for a 5/16-inch valve stem.
What valve guide size is required?The seal is designed to install on a .530-inch outside-diameter guide.
What is the seal's outside diameter?The metal body measures .575 inch outside diameter.
Is this a universal vehicle fitment?It is universal only by verified dimensions. Compatibility depends on the cylinder head, guide machining, valve stem, retainer, spring, and available lift clearance.
Can it be installed on an unmachined guide?Installation requires the guide diameter and finish specified for this positive-style seal. The cylinder head should be measured and machined by a qualified engine builder when needed.
Should clearance be checked after installation?Yes. Verify retainer-to-seal clearance at maximum valve lift and confirm the spring does not contact the seal body.
Installation Instructions
- Measure the valve stem, valve-guide outside diameter, spring inside diameter, and available retainer-to-seal clearance.
- Clean the valve guide and inspect the stem and guide for wear before assembly.
- Lubricate the seal lip and protect it from sharp valve-stem grooves during installation.
- Press the seal squarely onto the prepared .530-inch guide using the correct seal installer.
- Verify that the seal is fully seated and undamaged.
- Check retainer-to-seal and spring-to-seal clearance through the full valve-lift range before final assembly.
California Proposition 65 Warning: This product may expose you to chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm.
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