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Head Gaskets
Pontiac V8 Head Gaskets
Three Ways to Seal It — Head Gaskets for Pontiac V8s
The head gasket is the one part that has to hold cylinder pressure, coolant and oil all at the same time, and on a Pontiac V8 it also sets your quench and part of your compression ratio. Picking one starts with your finished bore, then your cylinder pressure, then the deck surface you actually have.
Butler splits Pontiac head gaskets three ways: composite gaskets for stock, bored and aftermarket blocks including the Butler Spec sets, multi-layer steel Cometic gaskets in Butler Spec water holes, and solid copper gaskets for specific drag race applications.
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1. The three families, and who each one is for
Butler carries head gaskets in three distinct constructions because Pontiac builds land in three distinct places.
| Composite, stock and bored blocks | Butler's own gaskets, made exclusively for BP from the original Fitzgerald dies used for GM in the 1960s and 1970s, along with Best Gasket GraphTite sets. These are the right answer for a stock rebuild or a naturally aspirated pump gas build, and they include the Butler Spec water hole versions. |
| Multi-layer steel | Cometic MLS gaskets with load-controlled embossments that seal with less clamp load and less bore distortion, cut to Butler Spec water holes in bores from 3.825" through 4.380". The choice once compression goes up, a power adder goes on, or you move to an aftermarket block. |
| Solid copper | dead soft copper in a wide range of bores and thicknesses, with or without water holes. Butler's own product copy is blunt about it — copper gaskets are recommended for very specific drag race applications only. |
2. Get the gasket bore right
Gasket bore is chosen off the finished cylinder bore, and the rule is not the same for every construction.
| Composite and MLS | match the stocked gasket bore to your bore range. Butler's 4.225" Cometic gaskets, for example, cover 400, 428 and 455 engines with bores from 4.120" to 4.211". |
| Copper | the gasket bore should run about .010" larger than the cylinder bore. Order copper by bore and thickness together. |
| Watch the overbore limits | a 4.200" bore composite gasket is not large enough for a .060" over 455, and Butler's aftermarket-block gaskets have water holes relocated for the larger bore so they will not work on a stock block. |
| Chamfers and valve notches | Pontiac blocks differ in bore chamfer and valve notch location. Those details decide which composite gasket you need, not the displacement on the tag. |
3. Thickness is a tuning decision
Once bore is settled, thickness sets quench and compression.
| Composite | Butler's own gaskets crush to approximately .045", and the Best Gasket sets are listed at .040" thickness with steel fire rings. |
| MLS | Cometic is available from .027" through .120", with .040" listed as the standard and most common thickness, and gasket volume published for each step so you can work the compression. |
| Copper | stocked from about .032" to .093", with or without water holes. |
| Do it with the pistons in hand | gasket thickness sets piston-to-head clearance as well as compression ratio. Decide both together. |
If you are not sure which family your build belongs in, call with your bore, deck height, compression target and fuel. That puts you on the right gasket the first time.
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.