Can I use this hole for filling oil?

Truck82 · Nov 9, 2024

Ok, so I ordered this nice set of valve covers on a kinda last minute order from LMC. Two Questions.

One, can I fill oil from this PCV/breather hole? (See picture below)

Two, if not, how would I go about getting an oil fill hole cut for a cap? Is this something I can do or is it even possible?

Are these valve covers only for the older engines with the filler tube up in the front of the intake?

Ok, so that was more than just two questions but any thoughts and knowledge on the subject will be much appreciated!

Thank you in advance!

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bucket · Nov 9, 2024

You can definitely fill oil through those. However, some cheaper covers occasionally have a baffle that doesn't flow oil as well as others and there's a small chance that it could be a slow process.

Truck82 · Nov 9, 2024

Thank you for the reply. Mine have baffles underneath. Would it hurt anything if I cut one side out? Seeing how the more expensive ones don’t have them this shouldn’t be an issue?

fast 99 · Nov 9, 2024

Wouldn't cut the baffle out unless necessary. PVC will suck oil or possibly spray out on breather side. Once it's out it's gone.

bucket · Nov 9, 2024

I wouldn't worry about it unless it actually is a problem. And even then, eh. An extra minute or two every oil change is no big deal.

Truck82 · Nov 9, 2024

Thanks guys! I guess I’ll just have to wait a minute or two longer when filling up with oil. Good thing it only gets changed every 10,000 miles anyway….

75gmck25 · Nov 9, 2024

You just need to put a rubber grommet insert in each of the holes. It might take a little experimenting, because there is one size grommet that fits well on a PCV valve on the driver side, and a slightly larger (inside diameter) rubber grommet for the breather on the passenger side.

Some of the rubber grommets have a baffle in the bottom, and some are wide open. You could used either one, since you have baffles in the valve covers.

mtbadbob · Nov 9, 2024

The old Chevy valve covers had an oil fill rubber plug that went into a valve cover hole.

PrairieDrifter · Nov 10, 2024

10,000..?

bucket · Nov 10, 2024

Truck82 said:
Thanks guys! I guess I’ll just have to wait a minute or two longer when filling up with oil. Good thing it only gets changed every 10,000 miles anyway….

You may not notice a difference. Most covers have a baffle that still flows oil well for filling.

Ideally, it will be the same as before, you don't won't have a dedicated oil fill hole. You'll just fill through the breather hole. If using an aftermarket open-type breather, just think of it as a vented oil fill.

Ricko1966 · Nov 10, 2024

mtbadbob said:
The old Chevy valve covers had an oil fill rubber plug that went into a valve cover hole.

Those aren't the right covers though. Do not try that,you will develop leaks everywhere if you plug one of those holes. If you are serious about wanting to use those valve covers and have an oil fill. Drill a hole with a hole saw, dull the edges the best you can and use and expanding rubber freeze plug as an oil cap

Truck82 · Nov 10, 2024

Ricko1966 said:
Those aren't the right covers though. Do not try that,you will devolp oil leaks,every where if you plug one of those holes. If you are serious about wanting to use those valve covers and have an oil fill. Drill a hole with a hole saw dull the edges the best you can and use and expanding rubber freeze plug as an oil cap

I’m not trying to plug the hole with anything that’s not supposed to be there. just wondering if I can fill oil through them. I’ll be putting a PCV valve in one and a breather in the other and was going to just pull one of those out every time I change the oil to fill through it. I take both out every oil change to check the condition anyway.

Ricko1966 · Nov 10, 2024

Truck82 said:
I’m not trying to plug the hole with anything that’s not supposed to be there. just wondering if I can fill oil through them. I’ll be putting a PCV valve in one and a breather in the other and was going to just pull one of those out every time I change the oil to fill through it. I take both out every oil change to check the condition anyway.

I was just letting you and everyone know,do not put an oil cap in one of those holes,a previous post mentioned the old rubber fill plugs. Just wanted to make sure everyone knew not to put a fill plug in one of those holes.

Truck82 · Nov 10, 2024

Ricko1966 said:
I was just letting you abd everyone know,do not put an oil cap in one of those holes,a previous post mentioned the old rubber fill plugs. Just wanted to make sure everyone knew not to put a fill plug in one of those holes.

Thank you

I didn’t know it could cause a problem but now I do and I won’t try it!

75gmck25 · Nov 10, 2024

PCV always need an "in" port in one valve cover and an "out" port in the other valve cover.

The PCV pulls constant vacuum toward the base of the carburetor and draws air and moisture out of the engine crankcase. The pop-up mechanism inside the PCV valve controls how much air is pulled in. The breather in the other valve cover is the air inlet to the crankcase, so you either need a breather cap, or use the original connection to a filter in the side of the air cleaner housing.

Can I use this hole for filling oil?

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