'73 318 how do you know if original engine mount rubber is good?

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Lasalle

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This is the type where the rubber is inside a cylindrical sleeve. I have removed many parts for repairs and access to the engine mounts is good now. If the rubber is OK I would like to just reuse the existing ones. It seems the conventional wisdom is that rubber is better than polyurethane at reducing vibration. This is not a high horsepower hot rod and I want smoothness. Are factory style rubber replacements available?
 
Does mobileparts know the answer to my question or does he/she sell parts?
 
He has great OEM parts. I know he has motor mounts also. I tagged him here he will chime in. Craig is a good one!
 
This is the type where the rubber is inside a cylindrical sleeve. I have removed many parts for repairs and access to the engine mounts is good now. If the rubber is OK I would like to just reuse the existing ones. It seems the conventional wisdom is that rubber is better than polyurethane at reducing vibration. This is not a high horsepower hot rod and I want smoothness. Are factory style rubber replacements available?


If they are rubber and more than a few years old they are already heading down.

You are in there. Change them out to poly and don’t look back.
 
Will I feel more vibration with the polyurethane?

I've never used poly spool type engine mounts, but I've used poly spool trans mounts, and the vibration increased a lot. When I've used the earlier biscuit-type poly engine mounts, vibration also increased.

One way to get a little more support for the engine is to use RTV silicone to fill the voids in the rubber of the mount. Let it cure for a couple of days, and install as usual. It will take some flex out of the mount, but any NVH added would be minimal. I've done that on more modern engines with good results.
 
This is the type where the rubber is inside a cylindrical sleeve. I have removed many parts for repairs and access to the engine mounts is good now. If the rubber is OK I would like to just reuse the existing ones. It seems the conventional wisdom is that rubber is better than polyurethane at reducing vibration. This is not a high horsepower hot rod and I want smoothness. Are factory style rubber replacements available?

Rubber inserts are available to replace the originals
1974 DODGE DART 5.2L 318cid V8 Motor Mount | RockAuto

Poly will result in less engine movement, but it does increase the vibration transferred. It's not a big deal, I run poly inserts in the spool style engine mounts with the 340 in my Duster.
 
I've never used poly spool type engine mounts, but I've used poly spool trans mounts, and the vibration increased a lot. When I've used the earlier biscuit-type poly engine mounts, vibration also increased.

One way to get a little more support for the engine is to use RTV silicone to fill the voids in the rubber of the mount. Let it cure for a couple of days, and install as usual. It will take some flex out of the mount, but any NVH added would be minimal. I've done that on more modern engines with good results.
I've done that before, but with windshield urethane.
 
I'm considering repairing the old ones with silicone/urethane. This seems like a great idea. Is this as good as getting new rubber? Does this remedy last or is it a temporary fix?
 
I'm considering repairing the old ones with silicone/urethane. This seems like a great idea. Is this as good as getting new rubber? Does this remedy last or is it a temporary fix?
No Sir, the additional material add to New Rubber will make em a Lil tighter, and stronger. At least you have the good mount set up. My 68 Coronet had the older biscuit style, kept shearing em off, even broke a torque strap! Gotta Love big block Mopar and a 4 speed!
 
They're really inexpensive, and the job isn't bad. A floor jack, block o wood, and think it's 5/8" maybe 11/16" on the nuts. A few of em are that "darn 1/8 th' of a turn" I did polys there and at the trans, also the rear, in my 74 Duster w a 340. It's a tight car...
 
In the end I reused the original engine mount brackets but just replaced the rubber spool type inserts. The Anchor brand spool inserts were actually made in USA.
 
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