Big Block Motor Mount Suggestions

[HawkRod]

I have a 1970 Road Runner with its original big block K-Member.

I am replacing my 383 engine with a 400 stroker that makes over 600 Lb-ft of torque. I have heard that stock motor mounts are not up to the task (which is what I currently have). I do not want to run solid mounts as this is a street driven car that I will drive extensively.

I have seen the Schumacher PolyLoc motor mounts, which look like they could be a decent choice, but any other or better suggestions for motor mounts?

As always, I appreciate the brain trust here at FBBO! Thanks in advance!

Hawk

(@PST looks like you have Schumacher PolyLoc mounts, although part number was not clear to me - is it POLYBXEPSM?)

 

[tnfastback]

I used the 440 source reinforced mounts. However only the drivers side mount is reinforced which I guess is ok. I also am putting a factory torque strap on just because it looks cool

 

[CoronetDarter]

I used Mity Mounts on the Coronet.
https://www.mitymounts.com/howtheywork.htm

600 lbs-ft stroker!!! Are you going to start a build thread?

 

[hunt2elk]

I went to using solid Moroso mounts after a failure of a Schumacher Polyloc. Never used the Mighty Mounts, but have not heard anything bad about them.

 

[68Moparmaniac]

I went to using solid Moroso mounts after a failure of a Schumacher Polyloc. Never used the Mighty Mounts, but have not heard anything bad about them.

What failed on the polyloc mounts? What was the beast these were bolted to?

 

[hunt2elk]

What failed on the polyloc mounts? What was the beast these were bolted to?

It was on a 451 making about 535hp. Oddly it was the passenger side that failed. Mike at Schumacher wanted it back and alluded to the fact he had some others do the same thing, although failure of the drivers side was far more common.

 

[68Moparmaniac]

It was on a 451 making about 535hp. Oddly it was the passenger side that failed. Mike at Schumacher wanted it back and alluded to the fact he had some others do the same thing, although failure of the drivers side was far more common.

So was it the vulcanizing that failed?

 

[HawkRod]

I used the 440 source reinforced mounts. However only the drivers side mount is reinforced which I guess is ok. I also am putting a factory torque strap on just because it looks cool

I never thought about this, but it certainly makes sense that only the driver's side is reinforced since that is the one that gets pulled on while the passenger side gets compressed.

I used Mity Mounts on the Coronet.
https://www.mitymounts.com/howtheywork.htm

600 lbs-ft stroker!!! Are you going to start a build thread?

Cool. The Mity Mounts seem to have the same idea as the Shumacher. I'll look these up.

I do have a build thread. In continuing my theme, it is called Hawk-Rod: The "Tune Up". In there, you can see my continuing follies as I try to pretend I'm an ace mechanic!!
https://www.forbbodiesonly.com/moparforum/threads/hawk-rod-the-tune-up.183169/

It was on a 451 making about 535hp. Oddly it was the passenger side that failed. Mike at Schumacher wanted it back and alluded to the fact he had some others do the same thing, although failure of the drivers side was far more common.

OK, so much for my response above about only needing the driver's side! Out of curiosity, it what manner did it fail? Any additional description would be appreciated.

Thanks,

Hawk

 

[hunt2elk]

So was it the vulcanizing that failed?

Yes. Mike recommended a bolt through drivers side mount and a torque strap until he got the problem figured out. He sent me these items free of charge. Standup guy imo.

 

[HawkRod]

I used Mity Mounts on the Coronet.
https://www.mitymounts.com/howtheywork.htm

Maybe I should wait on the Schumacher Polyloc's if they are having issues. Plus, they seem to be out of stock in several places I looked. Maybe that's because he is working on them?

Price seems reasonable on the Mity Mounts so I just ordered a set. I need to get this engine back in and get some miles on this thing before the trip to make sure everything is working!

Gentlemen: Thanks for the help as always!

Hawk

 

[ddemon440]

Yes. Mike recommended a bolt through drivers side mount and a torque strap until he got the problem figured out. He sent me these items free of charge. Standup guy imo.

Do you have a picture of the bolt through mount? Do you know what size bolt? One bolt, two bolts?

 

[70chall440]

I usually use stock mounts with a torque strap.

 

[qkcuda]

Hawk, I used a home made torque strap. I only drilled one hole in the pinched edge of the K member. I used a left over strut rod bushing to cushion it a bit. Worked great.

 

[dadsbee]

Since 1979...

 

[Hemirunner]

Stock mounts with a torque strap on it to limit movement will work fine.

 

[hunt2elk]

Do you have a picture of the bolt through mount? Do you know what size bolt? One bolt, two bolts?

https://www.forbbodiesonly.com/moparforum/threads/mancini-mag-motor-mounts.191262/#post-911533749
I sold this set of them a while back. One bolt, I don't know the size. If you call Mancini, they could tell you.

 

[HawkRod]

Thank guys. I ended up ordering and installing the Mity Mounts. They look stock but have the built in lock that should work like a torque strap. They fit my car "image" of trying to look stock while also trying to disguise as much as possible any modern upgrades.

The driveline goes back in this weekend, so hopefully in a couple of weeks we'll see how they work!

Hawk

 

[Nate S]

Back in the day we used to run a 3/8” link chain from the water pump housing to the frame rail. Let the engine wiggle on the soft mounts but went solid when you stepped on it. Doesn’t look sexy these days.

 

[BLK 68 R/T]

I drilled my drivers side mount and put 2, 3/8” grade 8 countersunk Allen head bolts through it.

 

[HawkRod]

Back in the day we used to run a 3/8” link chain from the water pump housing to the frame rail. Let the engine wiggle on the soft mounts but went solid when you stepped on it. Doesn’t look sexy these days.

Yes, my car had the remains of a chain like that when I got it (connected to frame rail, but not to engine). It had definitely been used for some stoplight drag racing in its day!!!

Found pictures of it!

 

[matthon]

I drilled my drivers side mount and put 2, 3/8” grade 8 countersunk Allen head bolts through it.

Imo, this is the way to go, passenger mount too, and torque strap or chain.
I have no experience with the mity mounts though.

Out of curiosity, it what manner did it fail?

Poly locs will always fail, it's built into the design. I've posted on this before, been through 3 sets of mounts, Schumacher sent free, asked me to install torque strap, build heat shields, etc. Both mounts failed on my a-body and the driver's side mount is forward, nowhere near header.

Each side of the mount within the poly do not touch, not the issue really, the problem is they are vertical and can easily slide past each other.
I went over this with Schumacher as well, but no design change.
I eventually bought their powder coated brackets and mounts and the passenger steel, engine side, bracket bent within 30 seconds.

I always say if you have poly locs and they haven't failed, look closer.