Slight leak from under head near distributor, how bad?

Joined
Jun 7, 2016
Messages
660
Location
Connecticut
Last night I noticed a slight leak from under the head near the distributor. There is a small casting feature on the head and from searches it appears the gasket gets skinny here. The engine has good compression otherwise. This may have been there for a long time and I never noticed it because of gunk I figured was from the old leaky stamped valve cover or the side cover.

Seems to be oil. If I spray it I can see a tiny bubble pulsing out.

Retorque head bolts? Pull the head? Run it?

Here is a photo of the spot in question from when I got the rig
C2616B37-2DD0-4D3D-A036-C605EA839AEE.jpeg


The photo below is not mine but to show where I am seeing this (mine is an F155)
A545D45F-55D0-4537-9075-882927E08E05.jpeg
 

1911

chupacabra
Joined
Aug 11, 2006
Messages
6,678
Location
Parker County, Texas
You're sure it's the head gasket, and not just the pushrod gallery side cover? The pushrod gallery cover is a pretty common leak; folks tend to over-tighten it and squeeze the cork gasket out.

If it is a head gasket leak, you could try re-torquing the head bolts, but there's enough pressure from the cylinders to blow out a channel in a head gasket pretty quick, and chances are you'll end up pulling the head and replacing the gasket.
 
Joined
Jun 7, 2016
Messages
660
Location
Connecticut
You're sure it's the head gasket, and not just the pushrod gallery side cover? The pushrod gallery cover is a pretty common leak; folks tend to over-tighten it and squeeze the cork gasket out.

If it is a head gasket leak, you could try re-torquing the head bolts, but there's enough pressure from the cylinders to blow out a channel in a head gasket pretty quick, and chances are you'll end up pulling the head and replacing the gasket.
Im 95% sure its the head. I will try to take some video. Since it is oil, adjacent to that passage and with the raised area on the head casting, I was not sure if this was a known issue.
 
Joined
Jun 7, 2016
Messages
660
Location
Connecticut
That's not anywhere near the oil galley plug is it?
I think it’s forward of that. Oil galley plug has been the top result in my searching. It seems to be in line with the #1 bolt in the torque sequence which is inset from the outside edge. Between that bolt, the head gasket design and the casting feature I didn’t know if this was a common weak link.
 
Last edited:
Joined
Feb 3, 2020
Messages
445
Location
Stanwood, WA
That is just a drain back hole and not under pressure so nothing should bubble out of there unless: 1. You have a ton of crankcase pressure and no pcv or other venting; 2. If you have a crack or seam in the head gasket all the way to there from a pressurized oil port or cylinder. There’s no pressurized oil in the head except from that copper line to valve train (on a 1F) and if it’s being pressurized from a cylinder and oil is coming out, it’s more than just a head gasket issue.
In short, I’d be looking at the pushrod cover gasket. But to bubble regardless says it’s under pressure, which it shouldn’t be.
 
Joined
Jun 7, 2016
Messages
660
Location
Connecticut
That is just a drain back hole and not under pressure so nothing should bubble out of there unless: 1. You have a ton of crankcase pressure and no pcv or other venting; 2. If you have a crack or seam in the head gasket all the way to there from a pressurized oil port or cylinder. There’s no pressurized oil in the head except from that copper line to valve train (on a 1F) and if it’s being pressurized from a cylinder and oil is coming out, it’s more than just a head gasket issue.
In short, I’d be looking at the pushrod cover gasket. But to bubble regardless says it’s under pressure, which it shouldn’t be.
That was what I thought looking at it. PCV was replaced a while ago and I’ve got a breather filter on the valve cover.
Is there normally a raised section of the head?
1FCE506D-2590-454A-863F-3386E4781C44.jpeg
 
Joined
Feb 3, 2020
Messages
445
Location
Stanwood, WA
Yes, that raised section is normal; pic of same spot on my 71 1F below. I still don’t get why it’d be pressurized there. Can you run it with the oil fill cap removed and see if it still does it? If you try that, put your palm on the fill cap and see if it’s building pressure? Is it overfull on oil? The only pressure the gasket is sealing is coolant and combustion. You can see from the image you posted with the head off how far combustion pressure would have to go to cause that.
A random thought: maybe it’s not a leak at all but harmonics of the running engine just causing stuff to bounce and look like it’s bubbling right there? Wipe it really good and dry and see what happens?
3A93F4B5-041A-45D1-B5A9-AA740C4A3091.png
 
Joined
Jun 7, 2016
Messages
660
Location
Connecticut
Thanks for the insights! Im going to check these things and will report back.

Ill plan on doing what is listed above such as verifying my oil is not overfilled, doing a compression test, replacing the side cover gasket and tracking down a new PCV valve and hose just to hit to low hanging fruit first. I will plan on checking the head bolt torques and going from there. Thanks again
 

Users who are viewing this thread

Top Bottom