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Oil Fill Caps/Baffles
Pontiac V8 Oil Fill Caps/Baffles
Fill It and Baffle It — Oil Fill Caps/Baffles for Pontiac V8s
The oil fill cap is how you get oil into a Pontiac V8 and one of the two holes that decides how the crankcase vents. A baffle is what keeps that oil from going straight back out the hole the moment the engine builds pressure. Both live here, and both are decided by how your valve covers were drilled.
Butler machines its own 1-5/8" CNC fill caps from 6061 billet with a bolt-on bung, and stocks a factory-style chrome cap, a push-in billet cap, and bolt-in baffles from Butler, Moroso and Motion Raceworks with AN fittings for an evac system.
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1. Which fill cap your covers take
There are three ways a cap attaches to a Pontiac valve cover, and the cover you own picks one for you.
| Threaded billet, bolt-on bung | the Butler CNC 1-5/8" cap, made in house from 6061 billet with a 1-1/4-12 straight thread, a 4 on 2" diameter bolt circle and a 9/16" bung height. Mounting hardware and bung O-rings are included, and the easy twist cap comes off without a pry bar. Billet finish that can be polished to a high gloss, or black powder coat. |
| Push-in | a billet aluminum push-in cap that seats in a grommet rather than a threaded bung. It needs the 1" ID by 1.200" OD grommet, so it is the cap for a cover drilled to that size. |
| Factory-style chrome | a chrome filler cap for a 1968-72 Pontiac that fits the 67-77 stock chrome covers. It wears an S on the rivet rather than the correct marking and the chrome is fair, but it looks and works well on a driver. |
2. Baffles and evac bungs
A baffle is a plate between the inside of the cover and the hole above it. Without one, oil thrown off the valvetrain goes out the breather or the evac line.
| Butler Bolt In Baffle Kit | a billet aluminum plate with mounting hardware that keeps oil out of an evac bung or breather. Bolt holes go 2" across, with sealer around them and thread lock on the bolts. No weld-in bung included. |
| Moroso bolt-on baffle, -10AN | adds a female AN fitting to a steel or aluminum cover without welding. The billet plate seals with an O-ring and hardware, and an interior baffle is included as an option. |
| Motion Raceworks bolt-in baffle kit | a bolt-in evac bung with a -8AN fitting in a silver anodized billet housing, with hardware, a drilling template and the O-ring fitting in the box. |
3. Getting the hole right
Almost every problem on this page is a hole problem.
| Bolt-in versus weld-in | the Butler cap accepts either style of bung. The bolt-on version is the one to pick if you do not want the covers off the car and on a welding table. |
| Ordering new covers | if Butler is building your valve covers, the fill cap is installed for you — pick one oil fill location per set and say where it goes in the order notes. |
Pick the cap that matches how your covers are drilled, then put the baffle under it. The baffle is the cheap part of the job and the one people skip right up until they find oil where it should not be.
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.