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Motor mount vs Frame mount question
#1
So tonight a buddy helped me locate the metallic knocking/rattling sound when accelerating.  Turns out the engine is flexing and the fan is hitting the fan shroud. Probably a bad motor mount, my buddy suggested.

I didn't look at it close enough (shame on me) to see if it's the motor mount or the frame mount (or both?). The driver's side of the engine goes up, so that side probably has a crack or something.

The motor mount part I found quick enough, including this one: https://ebay.to/2wO4AYv however the frame mount brackets seem to be harder to find and/or much more expensive, like this one: https://secure.cougarpartscatalog.com/d1...attribs=84

So my question is: should I replace the frame mounts and motor mounts, or should I remove them and see which, if any, are broken/cracked? Is it more common to have the motor mount damaged and needing replacing, or the frame mount?

I'm kicking myself that when my buddy was helping me troubleshoot, I should have looked closer to see if the flexing/rising engine on that side was causing the motor mount to separate or the frame mount. I'll do that I guess, but I thought I'd ask anyway.

BTW, this is a '72 vert with 351C 4v.

Thanks,

- Dan

Crazy! Fun!

"What!? You wanna buy a '72 mustang convertible and fix it up?!  That's CRAZY!... sounds FUN!"
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#2
The frame bracket is all steel, so less likely to be broken. The motor mount is rubber and steel, and on 71s and 72s when the rubber fails the motor can move quite a bit. 73s have an encapsulated style motor mount and don't move as much. However, they aren't directly interchangeable.

Motor mounts have been discussed several times on the forum. Rackerm has done a lot of research on them:
https://www.7173mustangs.com/thread-fan-shroud--31440

More threads can be found by searching the forum.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#3
if the frame side is cracked, broken etc. u can grind it and weld it and even reinforce it on inside if needed. the engine side mounts are easy to get at local auto parts and something like 20 bucks. the clam shells are closer to 200 AND u need to replace the lower mounts too.
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#4
That eBay listing is not correct - Convertibles us a different mount than the sportsroof and hardtop.

I believe this is the correct mount for 71-72 convertibles. If the driver's side is broken, it's time to do that passenger side as well.

http://www.mustangsunlimited.com/Mustang...rtible.axd


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#5
Man, I love this forum!

Hemikiller, thanks for the link. I had been looking at mustangsunlimited but somehow didn't find those exact set. It looks like you just flip them for the other side so I'll get 2 and be good to go.

I'm going to check it again this weekend to see where the flex/movement is happening. Yeah, if it's the frame mounts maybe I'll fix rather than replace because they seem pretty expensive & hard to find. Hopefully it's just the motor mounts and I'll be good to go with two from mustangsunlimited.com.

Thanks all!

-Dan

Crazy! Fun!

"What!? You wanna buy a '72 mustang convertible and fix it up?!  That's CRAZY!... sounds FUN!"
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#6
I've broken a couple of the motor mounts, never broken a frame stand.


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#7
Back in the day the hot rodders used to run a piece of chain from the exhaust manifold to the frame so that when the motor mount separated the engine couldn't rotate too far. It's not a matter of if, but when.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#8
Thanks, all! Good info. I ordered replacement motor mounts. I'll start with those and see how the frame mounts look when I'm putting in the new motor mounts.

It's funny, because the goal is to strip it down and rebuild it, but I realized that I've never actually _pushed_ the engine because of it's tendency to rotate when given a bit of torque and causing the fan to clatter against the shroud. So I've never taken it about 2500 RPMs. I think if the engine would stay in place, it might show some serious chutzpah, and I'd love to see that (and hear it!) before the strip down really gets started.

I am a bit worried that I'll keep finding excuses to delay the actual strip down, but maybe winter will cure that. Nothing like a convertible... in Colorado... in winter... (and where the heater seems to be missing, btw)... to encourage one to get started in the restoration. :-D

-Dan

Crazy! Fun!

"What!? You wanna buy a '72 mustang convertible and fix it up?!  That's CRAZY!... sounds FUN!"
  Reply
#9
Wait until you start your tear-down, then the fun will really start. You can tell us about the crazy part then Smile



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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