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Breathers- Stock and Aftermarket
Pontiac V8 Breathers- Stock and Aftermarket
Vent It Right — Breathers- Stock and Aftermarket for Pontiac V8s
A breather is how a Pontiac V8 gets rid of the pressure the pistons push past the rings. Vent it badly and you push oil out of gaskets; vent it well and the crankcase stays where it belongs. This category covers the whole range, from a factory replacement chrome cap to a full crankcase evacuation kit.
Butler stocks push-in and twist-in breathers, filtered and hooded units with washable elements, oil separators from RPC and Moroso for plumbing into the air cleaner or a header evac, plus correct-style breathers for 1959-64 and 1965-67 Pontiacs.
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1. Factory replacements
If the car is going back together the way it left the plant, the breather is a visible part and the wrong one shows.
| 1959-64, except Super Duty | the stock chrome push-in breather for those early covers. |
| 1965-67 GTO, LeMans and Tempest | an OEM replacement chrome twist-on oil breather cap with OIL and AC marked on the top, which is what a correct car should be wearing. |
| 1967-77 stock chrome covers | these take a small-OD-neck round push-in breather working with the small factory grommet, and either the factory-style twist-in cap or an aftermarket twist-in breather cap on the fill side. |
2. Push-in, twist-in, or filtered
The attachment style has to match the cover. The element style is up to you and how hard the engine works.
| Push-in | the breather body seats into a rubber grommet. Billet aluminum push-in units in black or polished measure 2.35" in diameter and 2" tall, 1.75" from the top to the grommet surface, and they need a 1" grommet in a 1.25" hole. |
| Twist-in | a 3/4" neck that locks in rather than pressing in, in a round top style at 2 3/4" diameter. Handy where a push-in keeps working its way loose. |
| Positive locking | a Moroso billet filtered breather with a threaded 1/2 NPT outlet that fits 1.25" holes and locks positively instead of relying on the grommet alone. |
| Filtered and hooded with washable elements | a serviceable element you clean instead of replace. Both styles seat straight into a 1.25" hole and need no grommet at all. |
3. Oil separators and crankcase evacuation
A plain breather vents to atmosphere. A separator catches the oil mist on the way out so it does not end up in the air cleaner or on the firewall.
| Chrome oil separator | chrome-plated steel with an internal foam disc and a baffle system that keeps oil out of the air cleaner. It is made for plumbing the crankcase into the air cleaner or running with a header evac system, and it fits a 1.22" hole. It does not come with a grommet. |
| Moroso separators | one version uses the same internal foam disc for a 1.22" hole; another is a positive locking separator with a tube sized for 3/4" hose, zinc-plated steel, 3.024" in diameter and 1.967" tall, bolt-on attachment, sold individually and without grommets. |
| Crankcase evacuation kit | the full Moroso kit with two each of oil separators and breathers, breather and filler cap grommets, one-way check valves and weld-in nipples for the header collectors. Read the note before you buy — it is not intended for applications with mufflers. |
4. Hole size decides everything
Buy for the hole in your covers. This is the trap on the whole page.
| 1.25" hole | the aftermarket standard. Billet push-in breathers, filtered and hooded units and positive locking breathers all live here. |
| 1.22" hole | what most of the oil separators are sized for. Close to 1.25" on paper, different in the hand. |
| 1" hole | the factory size. A billet 6001-style breather will not fit a stock valve cover with a 1" hole, and neither will a hooded washable unit. That cover takes the small-neck breather and the 3/4" ID vent pipe grommet. |
Decide first whether you are venting to atmosphere or plumbing the crankcase somewhere, then measure the hole, then pick the part. Doing it in that order is the difference between a clean engine bay and an oily one.
Not sure what your Pontiac needs?
Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.