Engine Mounts, P15; Caution

[Sam Buchanan]

The information in this thread is scattered over multiple threads with unrelated titles. For archiving purposes the info is condensed in this thread so future owners can more easily find it.

 

The rear engine mounts in my '48 P15 were totally shot so I ordered new ones from Andy Bernbaum. They arrived promptly and looked like the mounts I've seen advertised from other vendors. The lower mount was thicker than my old set so longer, 4-inch bolts were necessary to install the mounts. The engine could be jacked up sufficiently to insert the upper mount into the frame crossmember. I noticed the new mounts were quite hard....it wasn't possible to press a thumbnail into the material. I pulled the bolts up snug and everything looked as it should.

 

As soon as the engine fired for the first test drive it was obvious a large amount of vibration was being transmitted into the car. Matter of fact, it was really unpleasant. After the first test drive I backed off the torque on the bolts and tested again. Significant vibration was still present, especially around 40mph in third gear. The engine smoothed out at higher speed.

 

I have changed to nyloc nuts on the bolts so they can be torqued only enough to hold the mounts and lower washers in place. There is still more vibration that I like....but it seems obvious these mounts are made out of a material that is much firmer than needed.

 

The reason for this thread is to caution owners that hard mounts are out there.....and you don't want them! Posts on the forum have indicated that softer mounts are available and if anyone knows a source for softer mounts it would be greatly appreciated if that info could be provided.

 

This is another case of replacing worn-out parts but ending up with a situation that is not what we expected.....old cars can be a character-building process..... 

 

UPDATE; See post #54 for the remedy to the harsh mounts....the lower mounts were the problem.

Edited August 31, 2019 by Sam Buchanan

[Cold Blue]

Sam, I was going to order new mounts for my car, but with the problems you describe, I hope someone is a source for soft mounts. I am going to do some web searching to see if I can find some soft ones. If I do I will post it. I am not going to replace mine until I find those soft mounts. Dadgumit! Now you have to go to the trouble of removing your new hard mounts and install soft ones....

[Sam Buchanan]

14 minutes ago, Cold Blue said:

Sam, I was going to order new mounts for my car, but with the problems you describe, I hope someone is a source for soft mounts. I am going to do some web searching to see if I can find some soft ones. If I do I will post it. I am not going to replace mine until I find those soft mounts. Dadgumit! Now you have to go to the trouble of removing your new hard mounts and install soft ones....

 

I relieved the torque on the bolts to the point where the washers on the bottom are just barely captured and the ride isn't too bad. Still enough vibes to feel but not enough to keep me from driving and enjoying the car. But, yes, buy soft mounts if you can find them....and let us know! 

Edited August 14, 2019 by Sam Buchanan

[Frank Elder]

maybe these ?

https://www.speedwaymotors.com/Universal-Bolt-Through-Engine-Mount-Cushion-Kit,1199.html?sku=7209314&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQjw4s7qBRCzARIsAImcAxb_00qGy1uCgTWQuil0xessuu_jTmT3GNccX7Y6jdF4fCaVFZAd4IQaAhwZEALw_wcB

Edited August 14, 2019 by Frank Elder

[Andydodge]

Sam.........I don't hold a brief for Bernbaums but did you contact them regarding the mounts and let them know the situation?..........andyd 

[Sam Buchanan]

1 hour ago, Andydodge said:

Sam.........I don't hold a brief for Bernbaums but did you contact them regarding the mounts and let them know the situation?..........andyd 

 

Andy, I have not, and I don't have any interest in throwing a vendor under the bus. This entire situation is still unfolding for me and my learning curve is steep. I didn't realize there were issues with some mounts until two days ago (had never purchased or installed old Mopar mounts) so I'm still in the process of evaluating my options. There are Mopar guys on the forum with far deeper background on this matter than I and I'm waiting to see what alternatives are available for those who need engine mounts. For some reason there doesn't appear to be much firm info bubbling to the surface, folks are laying low. I don't know how many manufacturers of mounts there are and how many of the mounts seen on various ads are coming from the same sources. Without definitive details I'm kinda in the dark.

 

But I will contact AB soon.

Edited August 14, 2019 by Sam Buchanan

[desoto1939]

Sam HAve you contacted Steele rubber products. They make new motor mount with fresh rubber and should be softer. Yes the NOS mounts can harder up over the years so if they are around a cheap price might be too hard to use in a car or truck.

 

Always ask for new rubber.

 

Rich Hartung

Desoto1939@aol.com

[Eneto-55]

I wonder if pulling them out again (arg!) and drilling a number of holes through them, far enough out that they don't enlarge the center hole, but close enough that they all come under the washers would help.  (The idea being that with less material they would be softer.)

I haven't looked for them myself, but wonder if any of the sources give any kind of hardness info.  If not, it will be trial & error to find the right match, and then who knows if the next batch would be the same hardness.

Edited August 15, 2019 by Eneto-55

[Sam Buchanan]

2 hours ago, desoto1939 said:

Sam HAve you contacted Steele rubber products. They make new motor mount with fresh rubber and should be softer. Yes the NOS mounts can harder up over the years so if they are around a cheap price might be too hard to use in a car or truck.

 

Always ask for new rubber.

 

Rich Hartung

Desoto1939@aol.com

 

I don't have any reason to think these are NOS, they looked very fresh to me, were not in any marked packaging. Price was about the same as other sources I checked, just figured AB would be more likely to sell more of them and not have any problems. But......

 

I have not contacted any other vendors....yet. Just looked at Steele, they only offer revulcanization service for the upper mounts. Not sure what you use for the lowers....or if you even use a lower, maybe just the big washer.....I'm kinda confused on this.

 

 

Edited August 15, 2019 by Sam Buchanan

[Sam Buchanan]

2 hours ago, Eneto-55 said:

 

I haven't looked for them myself, but wonder if any of the sources give any kind of hardness info.  If not, it will be trial & error to find the right match, and then who knows if the next batch would be the same hardness.

 

I haven't seen any hardness info in any of the listings. All the ads I've seen except Steele look like the same mounts. Inconsistency batch-to-batch would make this a real crap shoot....

Edited August 15, 2019 by Sam Buchanan

[soth122003]

Hey Sam,

Just read the shop manual and it says there are hard rubber mounts that are identified by a wide white stripe moulded into the sides. If your mounts have the stripe Andy B might have sent the wrong ones(it's been known to happen). You might want to check and then give them a call.

 

Joe Lee

[JSabah]

I bought upper and lower rear engine mounts from AB and they seemed soft enough. I would call and discuss with them. I’ve received items that thru no fault of theirs were incorrect and they were fine with correcting or letting me return ( and refunded). 

 

I did have an issue with the new front (single) engine mount..... the studs were about 1/8” too wide but I just filed about 1/16 off each hole in the bracket. Should be ok but when I start it up for the 1st time (ever) in a couple of months, I’ll know more ?

[Frank Elder]

I have the thought of using Cummins style GEL type motor mounts, if they can dampen the vibration of a 4bt they can certainly do the job for the smooth L head 6.

[Sam Buchanan]

8 hours ago, soth122003 said:

Hey Sam,

Just read the shop manual and it says there are hard rubber mounts that are identified by a wide white stripe moulded into the sides. If your mounts have the stripe Andy B might have sent the wrong ones(it's been known to happen). You might want to check and then give them a call.

 

Joe Lee

 

No stripes. Interestingly, the mounts I have and all the ones I've seen listed in ads except for Steeles, don't match the illustrations in the manual (which I now have memorized...). The bottom mounts are so much larger than the ones in the manual that I had to use longer bolts. I'm wondering if whoever makes these mounts is shipping combinations of mounts that are different than they were in the original installation. Or maybe the illustration in the manual is for a different installation than the '48? I've learned (?) far more about engine mounts than I ever wanted to know......    ?

 

 

Edited August 15, 2019 by Sam Buchanan

[Don Coatney]

 

[YukonJack]

Did you replace the front motor mount too? Maybe if the front mount is compressed the new rear mounts raised the back of the engine higher than the front. This might effect your drive shaft angle which could cause a vibration. Just a thought. 

[Sam Buchanan]

1 hour ago, YukonJack said:

Did you replace the front motor mount too? Maybe if the front mount is compressed the new rear mounts raised the back of the engine higher than the front. This might effect your drive shaft angle which could cause a vibration. Just a thought. 

 

Interesting thought. The front mount has not been changed. But not the driveshaft, can depress clutch at speed and vibration goes away as engine rpm decays. 

Edited August 15, 2019 by Sam Buchanan

[Sam Buchanan]

18 minutes ago, Don Coatney said:

 

 

Looks very similar to what I installed. I had to use a 4" bolt instead of the shorter one that was removed. There was no bottom mount, I assumed it had deteriorated to the point it had fallen out. But maybe it never was there since the old bolt was shorter?? The illustration in the manual doesn't show a "thick" bottom mount.

 

Edited August 15, 2019 by Sam Buchanan

[kencombs]

I was reading through this and thinking about the symptoms.  You were able to reduce the vibrations by reducing the torque on the bolt.  If you study the assembly diagram carefully, it does not seem that that would be possible.  The lower washer's center hole is smaller than the tube it goes through.  So, when it is tightened it just clamps the tube between the nut, washer and the top flange.  The nut torque should not change the rubber's compression at all.

 

I'm confused.

 

Maybe the mount is just not the right set for the application.

[YukonJack]

2 hours ago, Sam Buchanan said:

 

Interesting thought. The front mount has not been changed. But not the driveshaft, can depress clutch at speed and vibration goes away as engine rpm decays. 

1 more thought. Front mount compressed and transferring vibration through the saddle mount bracket to the frame. Might not have been a problem with worn rear mounts, but once that was corrected the next weakest link became a problem.

[Sam Buchanan]

2 hours ago, kencombs said:

I was reading through this and thinking about the symptoms.  You were able to reduce the vibrations by reducing the torque on the bolt.  If you study the assembly diagram carefully, it does not seem that that would be possible.  The lower washer's center hole is smaller than the tube it goes through.  So, when it is tightened it just clamps the tube between the nut, washer and the top flange.  The nut torque should not change the rubber's compression at all.

 

I'm confused.

 

Maybe the mount is just not the right set for the application.

The diagram does not match the mounts that are sold for our application. The tube is not long enough to extend all the way through the thick bottom mount. Tightening the bolt compresses the mounts and makes them "harder". I have the bolt set now so the mounts aren't compressed. Yes, the mounts now available appear to be different from what was originally installed. The photo Don posted is what is now shipped if you order mounts from any of the sources I found. Compare the bottom mount with the one in the manual illustration and you will see it is very different.

 

The education continues. ?

Edited August 15, 2019 by Sam Buchanan

[soth122003]

Hey Sam,

You might try and remove the lower mount. It's an easy task and when I changed my mounts I also did not have a lower mount. So when I changed mine I did not install the lower mount. I think the only reason for the lower mount is to reduce vibes transmitted by the mount bolt to the frame.

 

Joe Lee

[Sam Buchanan]

1 hour ago, YukonJack said:

1 more thought. Front mount compressed and transferring vibration through the saddle mount bracket to the frame. Might not have been a problem with worn rear mounts, but once that was corrected the next weakest link became a problem.

 

@Dodgeb4ya stated the following in posts in a different thread:

 

"Some new replacement mounts have rubber that's way too hard. Will cause vibration."

"The rubber should be soft enough to push a thumbnail into it."

 

The mounts I installed are much firmer than that. I think it is obvious that the mounts are just too hard.

Edited August 15, 2019 by Sam Buchanan

[kencombs]

Since I'll be facing this on my '56 PU and the mounts are similar I decided to take a look at what's available.

 

First find: https://www.ebay.com/itm/1939-1956-Dodge-Truck-Engine-Motor-Mount-Set-for-Straight-Six-FRESH-STOCK/183097598681?fits=Year%3A1956%7CMake%3ADodge&hash=item2aa177a2d9:g:f10AAOSw9vlaYRxs

Looks like NOS at first glance.  Until you examine the box in the middle.  The seller used an old Mopar rod bearing box as a prop to mislead potential customers.

But the text indicates 'fresh stock'.  No tellin' what it really is.

[Sam Buchanan]

42 minutes ago, kencombs said:

Since I'll be facing this on my '56 PU and the mounts are similar I decided to take a look at what's available.

 

First find: https://www.ebay.com/itm/1939-1956-Dodge-Truck-Engine-Motor-Mount-Set-for-Straight-Six-FRESH-STOCK/183097598681?fits=Year%3A1956|Make%3ADodge&hash=item2aa177a2d9:g:f10AAOSw9vlaYRxs

Looks like NOS at first glance.  Until you examine the box in the middle.  The seller used an old Mopar rod bearing box as a prop to mislead potential customers.

But the text indicates 'fresh stock'.  No tellin' what it really is.

 

Those mounts "look" identical to what I have and to all the other mounts I found. Steele's revulcanization service is the only exception I've seen. Compare the bottom mount to what is in the Service Manual illustration.....it ain't the same. But they should work fine with a longer bolt if they are soft enough.

Edited August 15, 2019 by Sam Buchanan