Pontiac Valve Cover Buying Guide
Valve covers are one of the most-asked-about parts on a Pontiac engine — and one of the easiest places to buy the wrong part. Height, rocker clearance, brake boosters, A/C compressors, breather count, and gasket choice all interact. This guide walks through every decision, in the order we work through it on the phone every day.
The three questions that pick your cover:
1) What's on top of the rocker studs (stock rockers, roller rockers, polylocks, stud girdle)? 2) What's beside the covers (power brake booster, A/C compressor or box, wiper motor)? 3) How does the engine breathe (breathers + PCV, or an evac system)?
Quick Picker — Height vs. What It Clears
| Cover | Height | Valvetrain It Clears | Watch Out For |
|---|---|---|---|
| Factory stamped steel / stock chrome (1965–72 styles) | ~2 1/2" | Stock rockers; most roller rockers with ball/nut. Polylocks are taller — add a thick gasket or a spacer. | Polylock contact; no baffles on 67–72 style. |
| RPC cast aluminum short (RPC-S6520 / RPC-S7659) | 2 1/2" | Stock-style rockers. | May NOT clear aluminum roller rockers. |
| Butler short covers — Billet (BPI-SVC-BIL), Fab BFA/BPI-SVC-FAB, short chrome (RPC-S9461) | 2 3/4" | All roller rockers, including polylocks. | Not enough room for a stud girdle. |
| Butler CNC-logo cast aluminum (BPI-VC line), PRW (PRW-4045510) | 3 1/4" | Most roller rockers and polylocks. | Check power brake booster clearance; will not work with stock A/C brackets; possible wiper-motor contact on 67–69 Firebird with thick gaskets. |
| Tall fab — BPI-TVC-FAB, Moroso MOR-68477 | 3 1/2" | Roller rockers, polylocks, most stud girdles. | Measure booster and A/C clearance before ordering. |
| Tall — Butler Billet (BPI-TVC-BIL), BFA tall fab, Edelbrock Classic (EDL-4130), tall chrome (RPC-S9300 at 3 3/8") | 3 3/4" | Stud girdles and shaft-mount setups. | Most likely to hit a power brake booster or A/C box — measure first. |
Rule of thumb: 2 3/4" clears all roller rockers. Stud girdles need 3 1/2"–3 3/4". Taller is never automatically better — every 1/4" of height is 1/4" closer to the booster.
Factory Style Covers
For a period-correct engine bay we stock the three common factory chrome styles:
| Year Style | Part # | Hole Layout |
|---|---|---|
| Early 1964 389 | AAU-N221K | Passenger side has filler tube; driver side blank/no hole. |
| 1965 389 | AAU-N221R | 5/8" rubber grommet hole on passenger side, twist-in cap/breather on driver side. |
| 1966 | AAU-N221T | Passenger side no hole; driver side hole for twist-in breather. |
| 1967–1972 (fits through '77) | AAU-N222 / kit AAU-N222-KIT | Small 1" O.D. breather hole one side, twist-in oil fill the other. No oil drippers. Breather: RPC-S9171 push-in with RAR-VCGR1 grommet. Oil fill: AAU-N225B factory twist-in, or RPC-S9617 breather/cap. |
Will factory covers clear roller rockers? Usually yes with standard ball-and-nut style adjusters. Polylocks are the problem — the lock stack sits taller than a stock nut, and the polylock can contact the underside of a stamped cover. The fixes, in order: run a 5/16" or 3/8" thick gasket, add a 3/8"–1/2" valve cover spacer, or step up to a 2 3/4" short aftermarket cover. Always spin the engine over by hand and look for witness marks before final assembly.
Butler Custom Covers
Butler Billet — the ultimate Pontiac cover
CNC-milled in our shop from solid 6061 billet with a thread-milled custom oil fill. Any of our engraved logos, or send us your own. Short 2 3/4" (clears all roller rockers) or tall 3 3/4" (built for stud girdles). Available evac-ready with bung and baffle installed. Shop the Butler Custom collection.
BFA hand-fabricated — the 20-year Butler staple
Bent and welded .125" sheet aluminum with an extra-thick CNC-milled bottom rail for a dead-flat gasket seal. Short 2 3/4" or tall 3 3/4", raw or black, evac option available. Same rule: short clears all roller rockers, tall accommodates girdles.
Butler CNC-logo cast aluminum — the value custom cover
3 1/4" tall with a thick 1/4" gasket rail and 5/16" stainless bolts included, in black, silver/clear anodized, or polished, ball-mill engraved with your logo. Tall enough for most roller rockers and polylocks. Fitment notes on this cover: check power brake booster clearance (a small-diameter booster may be required), it will not work with stock A/C brackets, and thick gaskets can create wiper-motor interference on 67–69 Firebirds.
Every aftermarket cover leaves a blank canvas — we ball-mill engrave logos (Pontiac, GTO, Firebird, Trans Am, Judge, Indian Head, Butler, or full custom) right here in the CNC shop.
Other aftermarket styles
RPC cast and chrome, PRW 3.25" aluminum, Edelbrock Classic 3 3/4" and Signature Series stamped covers. These come as-is with fixed holes and oil fills and cannot have logos added. Note the printed warnings: the 2 1/2" RPC cast covers may not clear aluminum roller rockers, and the 3 3/8" tall chrome covers may not clear a power brake booster or A/C box.
Engine-Bay Clearance: Boosters, A/C, Wiper Motors
Rocker clearance is inside the cover; the engine bay is the other half of the fight. Before you order, check three spots:
Power brake booster (driver side). The single most common tall-cover conflict. Measure from the valve cover rail on the head straight out to the face of the booster — that dimension has to swallow the cover height plus gasket (and spacer, if used) plus room to slide the cover off for valve adjustments. If it's tight, the options are a short cover, or a small-diameter booster.
A/C compressor and box (passenger side). Large factory compressors and evaporator boxes crowd the passenger cover and dictate where breathers and oil fills can go. Stock A/C brackets do not work with our cast CNC-logo covers — plan on a relocated/compact compressor setup or a different cover.
Wiper motor (67–69 Firebird). Sits close to the driver-side cover; a tall cover on a thick gasket can touch it. Measure before stacking height.
Do Valve Cover Spacers Work?
Yes — a billet spacer is the honest fix when you want to keep a cover you already own (factory chrome on a car with polylocks is the classic case) or need just a little more room for a girdle. The spacer bolts between head rail and cover and raises everything sitting above it.
| Part # | Spacer |
|---|---|
| BPI-1039 | Butler billet 3/8" (set) — rocker/polylock clearance and light girdle duty |
| BPI-1039T | Butler billet 1/2" (set) |
| RAR-VC40 / RAR-VC50 | Billet 3/8" / 3/4" (set) |
| RPC-S7669 | Polished 1" (set) |
| RAR-VC-HDW | Spacer stud kit |
Three things to plan for with a spacer: (1) longer fasteners — our stainless kits run 3 1/2" for short covers (ABO-SVCB) and 4 1/2" for tall (ABO-TVCB), or use the stud kit; (2) two sealing joints — you now have a gasket surface above and below the spacer (gasket both sides, or gasket below and a thin bead of sealer above); (3) the height goes somewhere — every bit of spacer is height added toward the booster, A/C, and wiper motor, so re-check bay clearance.
Breathers, Oil Fill, and Where to Put Them
Pontiac engines need to breathe to relieve crankcase pressure. We recommend at least 2 breathers — typically one in each cover. On a street engine the factory-style PCV in the valley pan stays in service and does the actual scavenging; the cover breathers are the fresh-air side. Bigger cubic inches and more ring blow-by call for more venting or a full evac system (next section).
Breather styles: factory push-in (RPC-S9171 with the small-O.D. RAR-VCGR1 grommet for 1" holes on 67–72 covers), twist-in for stock covers (MRG-2061), or the billet S6001 series — a multi-piece design with cleanable internal filters, offered plain or CNC-engraved with Pontiac, GTO, Firebird, Judge, Indian Head, and other logos in black or polished. S6001 breathers fit a 1.25" hole using grommet RPC-S4878 (1" ID / 1.25" OD).
Oil fill options: factory twist-in caps for stock covers, or on custom covers a bolt-in bung (BPI-VC-10002) or weld-in bung (BPI-VC-10003) with our billet screw-in cap (BPI-VC-10001, black BPI-VC-10001-BK, with or without the Butler logo). 12AN cap-and-bung kits (BPI-VC-10004-KIT) are available for plumbed setups.
Where we drill — and why
We drill breathers and oil fills centered between the end of the cover and the bolt holes, which lands the hole between rockers inside. Our standard layout: a breather at the rear of each cover near the firewall, and the oil fill at the passenger-side front where it's easiest to reach with a funnel. Locations are called out looking into the engine compartment — driver or passenger, front or rear. Large A/C compressors, brake boosters, and wiper motors can rule out specific corners, so confirm clearance at your chosen cover height before we drill. On custom cover orders, just type the locations into the option box (example: "oil fill — passenger front; breathers — driver and passenger rear").
When to Run an Evac System
Big-cube strokers build crankcase pressure faster than breathers can bleed it off. The tell-tale signs: the dipstick pops out of its tube, oil gets pushed out of the breathers, and rear main seals weep or leak. That's when it's time to stop venting and start evacuating.
An evac system pulls a slight vacuum on the crankcase (header-mounted evac kit or electric/belt pump). To work, it has to be the only air path — seal off every other external source. Running evac on existing covers means plugging the breather holes. Better, run our purpose-built evac covers: a single oil fill to get oil in, no breathers, and one AN fitting (-10 on the cast covers) located close to the pump with a welded-in baffle that keeps the system from sucking oil. Available in black or raw fab, cast (BPI-VC-3-EVAC family), billet, and tall fab versions, or we can add a bung and bolt-in baffle (BPI-1070) to covers you already own.
Supporting pieces: an adjustable vacuum relief valve (MOR-22637) to cap how much vacuum the system pulls, and vacuum control valves (GZM-VCV101A billet hi-flow, GZM-VCV103 budget) for the plumbing.
Which Gaskets Work
Two decisions: material and thickness. Rubber with a steel or composite core is the reusable, set-and-forget choice for aluminum covers. High-density cork seals great on stamped steel and lets you buy thickness — a 5/16" or 3/8" cork gasket is often all the polylock clearance a stock cover needs.
| Part # | Thickness | Material / Use |
|---|---|---|
| SPM-VS7035-CK-2 | 1/8" | Stock cork — factory-height covers, stock valvetrain |
| BOP-VCG45R-2 | 3/16" | Rubber, steel core — our go-to on aluminum covers; reusable (Olds 403: BOP-VCG25) |
| SPM-11765-250 / FPR-1627 / RPC-S7482-2 | 1/4" | High-density cork — first step up for clearance |
| SPM-11765 / EDL-7590 | 5/16" | High-density cork or reinforced composite — the common polylock fix |
| SPM-11765-375 | 3/8" | High-density cork — maximum gasket-only clearance |
Thick gaskets raise the cover just like a spacer does — recheck booster/wiper clearance, and remember the 67–69 Firebird wiper-motor note above.
Installing Covers — Gaskets, Sealer, Torque
1. Prep the surfaces. Scrape both rails clean and wipe with brake clean. On used stamped-steel covers, check the rail for dimpled bolt holes — flatten them with a hammer and dolly or the gasket will never seal.
2. Cork gaskets: sealer on the cover side only. A light coat of gasket tack or a thin bead of RTV glues the gasket to the cover; the head side goes on clean and dry. The gasket stays with the cover every time you pull it for a valve adjustment, and it won't tear or shift.
3. Rubber steel-core gaskets: install dry. No sealer needed — that's the point of them. They locate on the rail, seal at low bolt load, and reuse for years.
4. Snug, don't crush. Valve cover bolts want to be evenly snug — on the order of just a few ft-lbs, working end-to-end in a couple of passes. Over-tightening splits cork, extrudes rubber, and dimples stamped covers, and every one of those leaks. Load spreaders (MRG-9817 / MRG-63962) help stamped covers distribute clamp force. Our stainless bolt kits: ABO-KIT-VC (OEM hex), ABO-KIT-VC-BP (Allen, for Butler covers), ABO-SVCB / ABO-TVCB for spacered short/tall setups.
5. Recheck after heat cycles. Cork relaxes — re-snug after the first few drives. And before the covers go on for good, rotate the engine through two full revolutions and check the gasket rail and cover underside for rocker or polylock witness marks.
Quick Answers
How many breathers do I need? At least 2. Street engines keep the valley-pan PCV working with them; big-inch or race engines move to evac.
Will my factory covers clear roller rockers? Usually, until you add polylocks. Then: thick gasket → spacer → 2 3/4" aftermarket cover, in that order.
Do they clear polylocks? 2 3/4" and taller covers, yes. Stock stamped and 2 1/2" cast covers, plan on a thick gasket or spacer.
When do I need the tall covers? Stud girdles or shaft rockers. Otherwise stay short and keep your booster clearance.
Do I use sealer? Cork: light sealer to the cover side only, dry to the head. Rubber steel-core: fully dry.
Can spacers cause problems? Only if you ignore the height they add — recheck booster, A/C, and wiper clearance, and use longer bolts.
Not sure what clears on your combination?
Tell us your heads, rockers, car, and accessories and we'll spec the cover, gasket, and breather layout. Use our Tech Form or call 866-762-7527. Butler Performance · Lawrenceburg, TN