Can I use this hole for filling oil?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Truck82

Member
Joined
Nov 2, 2024
Posts
60
Reaction score
112
Location
Alderton
First Name
Christopher
Truck Year
1982
Truck Model
c20
Engine Size
350
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!

You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,390
Reaction score
28,166
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
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

Member
Joined
Nov 2, 2024
Posts
60
Reaction score
112
Location
Alderton
First Name
Christopher
Truck Year
1982
Truck Model
c20
Engine Size
350
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?
 

Truck82

Member
Joined
Nov 2, 2024
Posts
60
Reaction score
112
Location
Alderton
First Name
Christopher
Truck Year
1982
Truck Model
c20
Engine Size
350
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

Full Access Member
Joined
Oct 13, 2016
Posts
2,247
Reaction score
2,185
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
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.
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,390
Reaction score
28,166
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
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

Full Access Member
Joined
Apr 11, 2017
Posts
5,361
Reaction score
8,555
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
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
 
Last edited:

Truck82

Member
Joined
Nov 2, 2024
Posts
60
Reaction score
112
Location
Alderton
First Name
Christopher
Truck Year
1982
Truck Model
c20
Engine Size
350
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

Full Access Member
Joined
Apr 11, 2017
Posts
5,361
Reaction score
8,555
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
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.
 
Last edited:

Truck82

Member
Joined
Nov 2, 2024
Posts
60
Reaction score
112
Location
Alderton
First Name
Christopher
Truck Year
1982
Truck Model
c20
Engine Size
350
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 :D
I didn’t know it could cause a problem but now I do and I won’t try it!
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,247
Reaction score
2,185
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
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.
 

Latest posts

Forum statistics

Threads
44,057
Posts
948,510
Members
36,124
Latest member
dabsRus420
Top