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Help with 401 heads

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markbritt View Drop Down
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    Posted: Mar/20/2017 at 8:55am
I just completed a rebuild and paint of a 1973 401 engine and installed it in my Jeep CJ7.   After running the engine for a short time, I am noticing that there is a small amount of both oil and antifreeze weeping out of a factory accessory hole in the right front head. This hole is what I use for alternator mount!!!! It is not much - about a thimble amount of antifreeze/oil mix puddled on the timing chain housing.

I suspect that the head must be cracked on the inside causing both water from the water jacket and oil from the oil drain hole to sump.

While finding another 401 head may be impossible, can I consider using a head from an AMC 360 as a core for replacement? I have searched on this topic, but cannot find anything.

Any help would be appreciated. I spent a year (on and off) assembling and painting this engine to it looks show and now I may have to remove the darn head.

Note: I took an old 304 head and sliced about 1/2 of the edge off to see how deep the bolt hole goes as well as the surrounding oil gallery and water jacket. The blue dot is where the bolt hole is.



Edited by markbritt - Mar/20/2017 at 8:03pm
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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 9:31am
A 360 head for that year has bridged rockers. 73 401 was the last year for studded rocker arms. It would be easier to find 74 on up heads, but there are a few late 71 to late 72 heads out there. Just make sure the valves are the same size. I have latr 70 heads which are high compression 291 versions, which wont match due to compression differences. Though they had two different sized valves done for the heads. Some ended up on 4bbl 360 engines while mostly were installed on 401 engines. So I would assume a 4bbl 360 engine would have the large valves, but would need someone who knows heads of all years to chime in on verification.

I would pull the head and have a pro mag it and see if that area can be fixed. Much easier and less costly to redo another head.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akimmet Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 9:45am
Heads off a 360 will work just fine.
If I remember correctly, the 360 and 401 engines used the exact same heads for a given year. Only the 304 had different heads with smaller valves.
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tsanchez View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 9:50am
If its not leaking internally just stick a 3/8 set screw with sealer in the hole.
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Moffman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Moffman Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 10:59am
Got a pic of it? That's an interesting place for a leak
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 11:00am
MOst likely someone put too long a bolt and cracked the inside of bolt boss, just plug it

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 11:05am
Originally posted by Moffman Moffman wrote:

Got a pic of it? That's an interesting place for a leak


I bet at one time either the hole was chased too far with a standard thread chase and cracked when bottomed, or undo pressure was exerted with a bolt still attached, possibly dropped or hit face down to the ground when pulled out of an engine bay. That area is thin and would not be the spot I would yank an engine with. Diagonal from front driver to rear passenger. Not diagonal front passenger to rear driver side, even though you can bolt up the heads to mount a chain with for pulling.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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markbritt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markbritt Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 11:21am
Picture - yes I have several and will post tonight. I have one of those diag cameras on the long want, so I was able to get right up to the hole.

My main concern here is plugging the hole Yes, that will resolve the drips, but can this crack be large enough that anti will still flow into the oil behind the plug?
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Moffman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Moffman Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 11:39am
Originally posted by markbritt markbritt wrote:

Picture - yes I have several and will post tonight. I have one of those diag cameras on the long want, so I was able to get right up to the hole.

My main concern here is plugging the hole Yes, that will resolve the drips, but can this crack be large enough that anti will still flow into the oil behind the plug?


If you're lucky, you should be able to get away with plugging it with an insert and some sealer. To me the most concerning part is not only coolant but oil as well. How does your oil and coolant look, any cross contamination inside?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ghinmi Quote  Post ReplyReply Direct Link To This Post Posted: Mar/20/2017 at 2:45pm
If you end up needing a head, let me know.  I sold a large lot of parts to a buddy in Indianapolis including a bare 1973 401 head.  The other was damaged so only the one is usable.
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