1973 I6 258 engine head gasket/expansion plug leak

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   I bought a 73 AMC Jeep Commando, and the 6-cyl motor starts up just fine.  I drove it one mile around town to test the transmission, brakes etc. and it seemed to have enough power (although I didn't take it above 20mph).  After shutting it off I noticed this sizzling (video below) and oil puddle dripping down the block.  Looks like a head gasket issue.
Question - if I pull the cylinder head off to replace the gasket, should I send it out for a valve job while it's off?  And while everything is apart, should I take the opportunity to replace the timing chain, lifters, rods...

Don't fix it if it ain't broke vs. preventive maintenance.

Advice appreciated!

I'm wondering how far I should go - I don't think the engine has any other problems, though I have yet to check the compression.

Edited by NJCommando - Nov/29/2021 at 8:26pm

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NJCommando Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Nov/22/2021 Location: NJ Status: Offline Points: 9	Post Options Post Reply Quote NJCommando Report Post Thanks(0) Quote Reply Topic: 1973 I6 258 engine head gasket/expansion plug leak Posted: Nov/23/2021 at 11:56am
	I bought a 73 AMC Jeep Commando, and the 6-cyl motor starts up just fine. I drove it one mile around town to test the transmission, brakes etc. and it seemed to have enough power (although I didn't take it above 20mph). After shutting it off I noticed this sizzling (video below) and oil puddle dripping down the block. Looks like a head gasket issue. Question - if I pull the cylinder head off to replace the gasket, should I send it out for a valve job while it's off? And while everything is apart, should I take the opportunity to replace the timing chain, lifters, rods... Don't fix it if it ain't broke vs. preventive maintenance. Advice appreciated! I'm wondering how far I should go - I don't think the engine has any other problems, though I have yet to check the compression. Edited by NJCommando - Nov/29/2021 at 8:26pm

ramblinrev Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11542	Post Options Post Reply Quote ramblinrev Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 12:02pm
	Yes. If you're doing all that labor, get a valve job done. I replaced the head on my '74 a couple of years ago, and put new lifters in as well. (I know that in theory, a new cam and new lifters should be put in together, but I think for the driving I do, this will work fine.) I did put new rocker arms and pushrods in at the same time, so the whole upper end of the engine is new. Timing chain and gears is a good idea too. If the engine runs fine, your cam could be fine. If you pull the lifters (special tool is helpful to reach them) you'll see if you have any uneven wear on the lifter bottom, and then you can check the lobes more closely. Edited by ramblinrev - Nov/23/2021 at 12:05pm
	74 Hornet Hatchback X twins (since 1977) 62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981)

Heavy 488 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3557	Post Options Post Reply Quote Heavy 488 Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 12:10pm
	Leaky valve cover is more common than a head gasket. When was the last time the cover was removed? Oil return holes can be plugged with old valve stem seal fragments not allowing oil to go down

NJCommando Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Nov/22/2021 Location: NJ Status: Offline Points: 9	Post Options Post Reply Quote NJCommando Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 1:33pm
	Ramblinrev - "If you're doing all that labor, get a valve job done." Αwesome, thanks! About the valve cover - I don't see any seepage around it. I don't know the car's history other than it apparently sat for a few years. So I have my work cut out for me...and I'm sure I'll find more.

Heavy 488 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3557	Post Options Post Reply Quote Heavy 488 Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 4:07pm
	The driver side of the head has zero oil passages.

tyrodtom Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6214	Post Options Post Reply Quote tyrodtom Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 7:58pm
	That video wasn't well enough lite up to see much, or long enough. Was the engine just started ? That could be a leaking manifold gasket. You zoomed in so quick I couldn't see if we were looking at the runner of the intake manifold, or exhaust. If the exhaust gasket was leaking, it'd appear like that if the engine was just started and still getting rid of moisture. Or a leaking intake would look like that if it was running very rich, with gas pooled in the bottom of the intake runner.
	66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.

ramblinrev Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11542	Post Options Post Reply Quote ramblinrev Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 8:07pm
	The valve covers on these great engines are notorious leakers, especially in that '73 era.
	74 Hornet Hatchback X twins (since 1977) 62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981)

NJCommando Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Nov/22/2021 Location: NJ Status: Offline Points: 9	Post Options Post Reply Quote NJCommando Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 8:55pm
	I had started the engine several times before driving it and letting it run from cold start this hissing/burning wasn't apparent. Only after driving it around a bit did leaks become apparent (carb is leaking gas, tiny radiator leak), I got some smoke in the cabin and parked it. The area is pretty clean, not a lot of sludge. I'll take a better picture when I get back next week. Thanks all for the comments! I'm in the right place for sure

Fluffy73 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Nov/21/2007 Location: Castlegar, BC Status: Offline Points: 3059	Post Options Post Reply Quote Fluffy73 Report Post Thanks(0) Quote Reply Posted: Nov/23/2021 at 10:23pm
	I wouldn't call that a head gasket issue. Off the top of my head, I'm sure a few of those studs' holes penetrate through the the water jacket. One of them may have become leaky. Quite honestly, it's worth the effort to re-seal the intake and check the few studs that protrude from the head. Full top end rebuild? Probably not necessary.
	I am genetically incapable of being Politically Correct.

FSJunkie Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742	Post Options Post Reply Quote FSJunkie Report Post Thanks(0) Quote Reply Posted: Nov/24/2021 at 3:06am
	I think that is coolant steaming off, not oil burning off. The original embossed steel head gaskets corrode away on engines that did not have their coolant changed regularly until one day it leaks. I am almost certain that the exhaust manifold stud holes have a bottom to them and do not extend all the way into the coolant jacket. Coolant leaking around an exhaust manifold stud can be a result of inclusions, cracks, or corrosion of the head casting around the stud.
	1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited