Loose motor mounts on early cars

[sleeve-valve]

I have heard that some solid motor mounts should be left a little loose on some early cars because the frame can flex, causing the block to possibly crack. Is this correct and if so, what are the specific recommendations? For example which years does this generally apply to, how many motor mount bolts should be loose, and how much should they be loose?

[DonMicheletti]

That sounds like a bad idea. Loose bolts will lead to the bolts wearing and the holes being "wallowed" out.

While the frames do flex, the cars I am familiar with (like my '18 Buick) have 3 point mounts that allow the frame to flex without breaking anything.

[Spinneyhill]

Bad idea in my opinion. What if you forget to check them and the nuts fall off and the bolts fall out? Spring washers don't work if the nut is not tight!

 

Sounds like another myth to me.

 

[dictator27]

X3.  Not a good idea.

[Rusty_OToole]

I know on motorcycles loose motor mount bolts cause the worst vibration. My old BSA twin had a brace or head steady to the frame from the cylinder head, if the bolt worked loose you knew at once because the whole bike vibrated like crazy. Tighten it up and the vibration went away.

 

As others have pointed out your car was designed to have the engine bolted down tight and the frame was supposed to flex, far more on the rough uneven roads of the past, than on today's roads. The mounts were positioned so this flex did no harm.

[Bud Tierney]

This's a new one on me...

While you didn't specify what you meant by "early",, in my own history and experience (mid 20s cars up) I've never heard this before (to the best of my knowledge, I've not seen "solid" motor mounts, without any "cushioning" of any kind)....as with all the comments above, I would think leaving the engine rattling around would be MORE likely to break/bend/damage things..

Share with us where you heard this idea...

[sleeve-valve]

Thanks for all the replies. I heard about it quite a few years ago from a local older gent. Maybe it was something he did or learned about years ago when there was actually a different underlying cause of blocks cracking. As stated above, another myth disproven.

[Rusty_OToole]

One of the many crackpot theories floating around the early car world.