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Discussion Starter #1
I've been chasing a vibration coming through the steering column on my 66 ever since finishing my muncie swap and I'm starting to narrow it down to a combination of, i think, two things.

I think my headers are contacting the pitman arm or sitting very close to it which would explain why it seems to get worse at steering lock and could explain why it is most pronounced at a certain RPM regardless of speed, gear, or if the car is even moving.

I plan on correcting this with some "persuasion" from a hammer when I remove them shortly to rebuild my upper control arms.

I also assume my motor mounts are partly to blame.

I realized there is a ton of space between the frame mount and the flange on the motor mount mount. I assumed I used the short and wide style vs the tall and narrow until I measured my frame mount.

The frame mount is just shy of 2 5/8" from side to side which should be the short style mount I believe since the tall is supposed to be 2 3/8". The weird part is the ears on my motor mounts seem to be somewhere around 2 3/4" or 2 7/8" apart...

I have washers in place now as a temporary solution but I'm going to be ordering new mounts (probably the Summit Poly ones) and it looks like the short and wide style is correct.

Here's my question.

As far as I know there are 3 styles of these mounts. The two I referenced above and a 3rd, oddball size that was 2.5" ear to ear according to a few sites I've found like this:

http://www.pozziracing.com/camaro_engine.htm

If that's true then what the heck are my current mounts from? Does anyone know of an early chevy style mount that would be that wide?

Thanks!

hotrod
 

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Discussion Starter #2
Finally swapped my old mounts for my new poly ones.

Here's the old vs new. No idea what my old ones are supposed to be for, they're wider between the mounting points than I think any of the chevy ones are supposed to be... Any ideas? More curious now than anything else.

Hopefully this helps solve some of my vibration issues...

 

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GM second design they were a recall.
Early mounts did not have the safety provision in case the rubber failed.
If the rubber failed the engine was free to travel up and down the engine bay at which when traveled up the throttle would stick wide open.

The first fix for that problem was Recall Engine restraint kits.

Then around 1971, the engine mounts were redesigned to incorporate a safety tab that kept engine movement in check if the isolator failed.

Which is what you have.

Gm lesson for the day....
 

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Discussion Starter #4 (Edited)
GM second design they were a recall.
Early mounts did not have the safety provision in case the rubber failed.
If the rubber failed the engine was free to travel up and down the engine bay at which when traveled up the throttle would stick wide open.

The first fix for that problem was Recall Engine restraint kits.

Then around 1971, the engine mounts were redesigned to incorporate a safety tab that kept engine movement in check if the isolator failed.

Which is what you have.

Gm lesson for the day....
Interesting, I was aware of the recall and the change in mount. I could have sworn we bought these new in the 2000's when I put the engine in.

If these are GM mounts why would the ears be so wide? These measure 2 7/8" which is way more than any of the info I've seen for GM mounts.
 

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There are two designs of engine mount dependent upon year of make and the engine used; a "tall / narrow" and a "short / wide". Looks like you have both.

Regarding why it's so wide, things can get bent and who knows how good the manufacturer was at holding the tolerance.
 

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Discussion Starter #6
I had thought the same thing about the 2 types of mounts but my new ones are the wide and short style (2 5/8 between ears) and the narrow and tall are 2 3/8.

My old ones measuring 2 7/8" seems like a huge difference and the ears don't appear to be bent. At least not 1/4" worth.

Guess this might remain a mystery unless I uncover a number on the mount or something so I can try to search online.
 
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