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Valve Seals & Spring Shims
Pontiac V8 Valve Seals & Spring Shims
Oil Control and Install Height — Valve Seals & Spring Shims for Pontiac V8s
Valve seals and spring shims are two small parts that decide two big things on a Pontiac V8: how much oil goes down the valve guide, and what the valve spring actually weighs on the seat. A seal that is the wrong diameter will not hold, and a spring installed at the wrong height makes the wrong pressure no matter what the box says.
Butler stocks Viton stem seals in .500" and .530" inside diameter for 11/32" stems, positive locking rubber seals, Pontiac O-ring style oil seals, and hardened valve spring shims in .015", .030" and .060" cut separately for cast iron and Edelbrock heads, plus a 48-piece shim kit.
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1. Which Seal Your Head Takes
Seal selection on a Pontiac comes down to the outside diameter of the machined boss on the guide, not to the engine size.
| .500" x 11/32", .620" outside diameter | the Viton seal typically used on stock cast iron heads with .500" valve guides, or heads that have had the valve guides milled for a seal. This is the common cast iron answer. |
| .530" x 11/32", .670" outside diameter | the Viton seal typically used on Edelbrock aluminum heads. Ordering the cast iron size for an Edelbrock head is the most common mistake in this category. |
| Cross reference | Butler's .500" Viton seal is the same part as Comp 517-16, Manley 24043-8 and Trick Flow TFS-30400454. The .530" is the same as Comp 529-16, Brodix USVS529V-16 and Manley 24045-8. If you already know a competitor number, you can match it directly. |
| Install tool | there is an option to add a valve stem install tool with the Viton seals. Pushing a Viton seal on over a lock groove without one is how seals get cut. |
2. Positive Lock and O-Ring Style
Not every Pontiac head is a candidate for a pressed-on Viton seal.
| Positive locking rubber | Butler's .500" x 11/32" rubber seal is the stock replacement for intake valves on certain Pontiac heads. It cross references to Edelbrock 9725, Pioneer OS-938-16, Howards 93360 and Trick Flow TFS-51400454. |
| O-ring style | Pontiac O-ring style valve oil seals are for stock type valves and sit in the lock groove rather than on the guide. Butler stocks them in sets of sixteen. On a genuinely stock rebuild this is what came out and what goes back in. |
| Guide machining | whether you can run a positive seal at all depends on the machine work. If the guides have not been cut for a seal boss, the O-ring style may be your only option until the heads go back to the shop. |
3. Spring Shims Set the Install Height
A shim under the spring raises the seat and shortens install height, which raises seat pressure. It is the cheapest tuning tool in the valvetrain.
| Three thicknesses | Butler stocks hardened shims in .015", .030" and .060", so height can be moved in useful increments rather than one coarse step. |
| The 48-piece kit | the shim kit contains sixteen each of .015", .030" and .060" in a 1.500" outside diameter with a .703" inside diameter, which fits both Edelbrock and cast iron heads. Buy the kit if you are building a set of heads and do not yet know what the measured heights will be. |
| Why it matters | a valve job sinks the valve and raises install height, which drops seat pressure. Shims put it back. The alternative is buying different retainers or having the spring pockets cut. |
4. Shim Inside Diameter Is Not Universal
This is the detail that separates the individual shim part numbers, and it is easy to miss.
| Cast iron heads | Butler's cast iron shims are 1.500" outside diameter with a .847" inside diameter. That larger bore clears the taller guide boss in a factory Pontiac head. |
| Edelbrock heads | the Edelbrock shims are 1.500" outside diameter with a .645" inside diameter. They are a different part, ordered separately in each thickness. |
| Hardened, always | every shim Butler sells here is hardened. A soft shim under a 700 lb open pressure spring will pound into the aluminum or the iron and the install height you carefully set will disappear. |
| Measure with the parts you are using | install height is checked with the actual valve, retainer and locks in the head. Shim to the number your spring spec calls for, not to a general rule. |
Order the seals by the head you have and the guide machining you had done, and buy the shim kit alongside your springs so you can set the height once and be finished.
Not sure what your Pontiac needs?
Email our tech team at tech@butlerperformance.com. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.