Help with 401 heads
Printed From: TheAMCForum.com
Category: The Garage
Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: https://theamcforum.com/forum/forum_posts.asp?TID=86263
Printed Date: Apr/19/2024 at 3:53pm
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Topic: Help with 401 heads
Posted By: markbritt
Subject: Help with 401 heads
Date Posted: Mar/20/2017 at 7:55am
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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.  
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Replies:
Posted By: 304-dude
Date Posted: Mar/20/2017 at 8:31am
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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 |
Posted By: akimmet
Date Posted: Mar/20/2017 at 8:45am
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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. |
Posted By: tsanchez
Date Posted: Mar/20/2017 at 8:50am
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If its not leaking internally just stick a 3/8 set screw with sealer in the hole. ------------- http://s192.photobucket.com/user/antonsan/media/jav1_zps87a70dce.jpg.html" rel="nofollow"> 
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Posted By: Moffman
Date Posted: Mar/20/2017 at 9:59am
| Got a pic of it? That's an interesting place for a leak |
Posted By: tsanchez
Date Posted: Mar/20/2017 at 10:00am
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MOst likely someone put too long a bolt and cracked the inside of bolt boss, just plug it ------------- http://s192.photobucket.com/user/antonsan/media/jav1_zps87a70dce.jpg.html" rel="nofollow">
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Posted By: 304-dude
Date Posted: Mar/20/2017 at 10:05am
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 |
Moffman wrote:Posted By: markbritt
Date Posted: Mar/20/2017 at 10:21am
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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? |
Posted By: Moffman
Date Posted: Mar/20/2017 at 10:39am
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? |
Posted By: ghinmi
Date Posted: Mar/20/2017 at 1:45pm
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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. ------------- 1975 Cherokee S - Turbo Hemi stick shift autocross/drag race/street 9.97 @ 140.4 |
Posted By: Moffman
Date Posted: Mar/20/2017 at 7:47pm
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From the pics I thought you pulled the head and cut it in half for a second there, was gonna say that's one way to check. Here's what I would do: Fill that hole and buy a bulltear intake manifold alternator bracket lol |
Posted By: FSJunkie
Date Posted: Mar/20/2017 at 8:32pm
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So you ruined a perfectly good 304 head.
------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
Posted By: 69 ambassador 390
Date Posted: Mar/20/2017 at 9:04pm
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Yeah!! Now that he cut a couple of pounds off it, no way is it gonna anchor his boat as well!! ------------- Steve Brown Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
Posted By: MidWestMind
Date Posted: Mar/20/2017 at 9:33pm
Yes they were. There was a guy trying to sell the 502-2's on fb last week as 401 only heads. |
Posted By: markbritt
Date Posted: Mar/21/2017 at 5:36am
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The head that was cut was a ruined 304 head, but the idea of seeing the thin section provided a good information on the water jacket and oil tubes. |
Posted By: Moffman
Date Posted: Mar/21/2017 at 9:39am
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Not sure if you want to go this route but may be helpful, Devcon makes an epoxy product that is titanium reinforced. Resistant to chemicals and max temp is 350 F. Here's some info on it. 90 bucks on amazon. http://www.devcon.com/UserFiles/File/Devcon_Catalog_LR(2).pdf https://www.amazon.com/Devcon-10760-Gray-Titanium-Putty/dp/B00065TM08 |
Posted By: markbritt
Date Posted: Mar/26/2017 at 9:37am
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Thanks to all on the advice and offering options. I talked with my machinist and he did offer a solution that would be to drill out the hole and insert a tapered plug. He also cautioned that since we don't know the extent of the crack, this may not solve the issue. Oil/Antifreeze leaking out of a hole is one thing, but since I don't know if anti is leaking into the oil, I have decided to pull the head and replace with a rebuilt 360 head I have. Mark |