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AMX Crossmember

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mbwicz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Topic: AMX Crossmember
    Posted: Sep/10/2020 at 9:52am
My 70 AMX had engine swaps in its history, and the motor mount area of the crossmember was torched out to fit the other engine(s). I acquired another crossmember from someone I trust. I believe that the one that was damaged was original to the car, the bolts holding it to the chassis were a bear to remove. 4 bolts with tapered seats and fine threads, like a European car's lug bolts.

Yesterday I got out the new crossmember to sandblast it, and notice that the 'replacement' piece appears to have had only one tapered seat bolt per side, and there is a witness that a flat washer was used on the second hole.

My gut feel is that the tapered bolt was used to positively locate the crossmember to the chassis.

Is there any reason to not trust one tapered bolt and one 'standard' bolt per side on this replacement crossmember?

In the pic, the original one is on the top, and the pen is pointing to the lack of a tapered seat on the replacement.

Thanks for any opinions.

Mike
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1948kaiser Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2020 at 12:03pm
my 72 gremlin with the factory v8 uses one bolt per slide and the one stud and a wheel nut per side. the stud gets put in first using anti-seize. takes two to hold the cross member up. then start the lug nut onto the stud and hand tighten to hold it in place. then the bolts using anti-seize should start by hand NO WRENCH and go in easily. that way they will not be cross threaded. the lug nuts line up the cross member into the correct position.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2020 at 12:10pm
If there was a problem with 1 taper per side i believe it would have been stumbled across many moons ago.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXFSTBK390 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2020 at 1:45pm
Originally posted by 1948kaiser 1948kaiser wrote:

my 72 gremlin with the factory v8 uses one bolt per slide and the one stud and a wheel nut per side. the stud gets put in first using anti-seize. takes two to hold the cross member up. then start the lug nut onto the stud and hand tighten to hold it in place. then the bolts using anti-seize should start by hand NO WRENCH and go in easily. that way they will not be cross threaded. the lug nuts line up the cross member into the correct position.

I recently rebuilt the 390 in my 68 AMX. The engine cross member is mounted exactly as you described.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mark09 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2020 at 5:30pm
The pen points to where a weld-nut is missing/knocked off.
Should have 4 tapered "blocks" to locate. 2 get stud-bolts 2 get 1/2"
Lug nuts. 1 nut and 1stud-bolt per side
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2020 at 6:11pm
Originally posted by 1948kaiser 1948kaiser wrote:

my 72 gremlin with the factory v8 uses one bolt per slide and the one stud and a wheel nut per side. the stud gets put in first using anti-seize. takes two to hold the cross member up. then start the lug nut onto the stud and hand tighten to hold it in place. then the bolts using anti-seize should start by hand NO WRENCH and go in easily. that way they will not be cross threaded. the lug nuts line up the cross member into the correct position.

That's the way every 71-74 Javelin I've worked on is. I think they took 2 of the blocks out as a running change to save money because it's not necessary.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mmaher94087 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2020 at 7:20pm
Mopar_guy is correct.  I had NOS cross members and they all were the later type made for 71 - 74s.
 
Edit to include:  If you are concerned about concours correct then knock two tapered nuts off your old crossmember with a cold chisel and use two old tapered bolts from the old assembly when installing the new.


Edited by mmaher94087 - Sep/10/2020 at 7:34pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Sep/11/2020 at 5:26am
Originally posted by mmaher94087 mmaher94087 wrote:

Mopar_guy is correct.  I had NOS cross members and they all were the later type made for 71 - 74s.
 
Edit to include:  If you are concerned about concours correct then knock two tapered nuts off your old crossmember with a cold chisel and use two old tapered bolts from the old assembly when installing the new.

Mike M is 100% correct it was a running change to the crossmember.  The old P/N supersedes to the one with single taper washer.  It was a mid year 1970 change from what I have seen from parting out dozens of 70 Javelin's and AMX's.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: Sep/11/2020 at 5:53am
Thanks for all the replies. I figured it was a running change along the way. Amazing all of these little details that show up when you start looking closely.

Mike
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2020 at 8:02am
Running change as Ross said. The second design is better. Two tapered locators like used in the first design will "fight" each other when it comes to front/rear location.
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