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390 engine

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rodhhrod View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rodhhrod Quote  Post ReplyReply Direct Link To This Post Topic: 390 engine
    Posted: Oct/19/2017 at 4:55pm
The saga continues on the 390, Question- on the drivers side the piston notches are all facing forward on the upper left about 10 oclock. The passenger side the notch  are facing forward but on the lower right section about 5 o'clock. is this common or is there a screw up here. According to the TSM the notch should be upper forward. Sure could use some help here.
Rod
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2017 at 6:01am
For a race engine 0.060" over might be okay, but thin cylinder walls mean higher temps, and a street 390/401 bored that much will likely have heating/cooling issues if driven any length of time. Not so important for drag cars -- can take time to cool between runs, and runs only last a few seconds.

jpnjim -- My best guess is the 401 as created because of competition more than anything else. Abernethey had set AMC up to compete head to head with the big three, and wanted to push AMC up into the mid priced segment (Buick/Olds/Pontiac/Mercury territory), and the competition all had 400 cubic inch engines. The upcoming changes in emissions/lower compression may have had something to do with it though, as cubic inches can make up for lower compression.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70amxvegas Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 2:26pm
60 over is ok .I bet there are a lot of them out there 60 over
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 12:44pm
+.060" is a lot for a 390/401,
but have the walls sonic tested before freaking out.

Factory spec says +.023 max,
rule of thumb says +.030" max,
but others have gotten away with more

+.060 = 4.225, but you don't know how thin the walls are until they're checked.

You could always list it for what you have in it,
hopefully the crank isn't +.030 already too 
^though even then the crabk can go .050+ on the mains, and the rods can go even more depending on what you're building.
71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rodhhrod Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 11:09am
All numbers check good and it does say 390 on it. Too bad, pulled a head off yesterday and has 60 over pistons in it. So much for original, damn, not sure what I am going to do now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 6:54am
68 TSM is fine. I would check the block casting number to make sure it's a 68/69 390 though. It's old, PO may have forgot what it came from or it may have been changed before he got it. I'm assuming the side of the block has 390 cast in? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70amxvegas Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2017 at 7:48pm
I will give you $801.00
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mmaher94087 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/16/2017 at 8:52pm
I used the '69 TSM to restore my '68 AMX. Other than cosmetics, everything was the same as far as I know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rodhhrod Quote  Post ReplyReply Direct Link To This Post Posted: Oct/16/2017 at 10:57am
Thanks all for the input. Here is the reason for asking,  I am a 70 guy so I have a 70 TSM and have access to a 69 TSM for reference. I just brought home a 390 complete motor, it supposedly came out of a 68 AMX, has everything on it except carb and air cleaner. Anyway bought it from guy from the Local AMC club that I have known for over 30 years, it has been under his work bench with the auto tranny still attached, I did not get that piece. It was a running motor when pulled, the only thing is that it is painted a orangeish red color, whick might be it has been rebuilt once before. Who knows, anyway I am going to start tearing down for inspection so I need the bore spec's to see where I am at, so would the  69 TSM work or do I need to get a 68 TSM book?
Sorry for the long winded story but that is it in a nutshell. Hope I didn't pay to much for it at $800
Any thoughts?
Thanks
Rod

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Oct/16/2017 at 6:52am
Originally posted by farna farna wrote:

68 and 69 are virtually the same, 1970 is a one year only model with different pistons and rods. It's basically a 401 destroked to 390. Marketing call -- I suspect last year of AMX two seater so they wanted to keep the 390 due to reputation, but were ready to produce the 401. "New" 401 came out with new body style Javelin/AMX...

Agreed.

Though a less honest company could have kept calling it a 390 (like Chevy did with the 396/402)

Do you think the reason for the bigger engines was to be ready for the new emissions standards and compression ratio drop after 1970/e71.

I guess it could have been the trend towards bigger/heavier cars of the 1970's too.

If the 304/360s seem choked off after 71,
and worse so after catalytic converters in 76,
imagine how they would have been without the extra torque from those longer stroke cranks. Ouch

Edit,
Just had a thought,
Is it possible developing the new "401" camshaft is what delayed the arrival of the 401?
Did late 70' 390's get the "401 cam"? (I forget now)


Edited by jpnjim - Oct/16/2017 at 6:55am
71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
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