Steel Engine Mounts constantly breaking off frame

[Slash]

I've got an old Ford 351 Windsor that keeps breaking steel mounts constantly. Is there any other type of mounts I can use that should at least help a little? It's a once a week/2 week thing and the bill is adding up. We just got it back on the road (hasn't been drivin as of lately but the issue remains) and we want to remedy or at least try to remedy this problem. It is not stock and I know thats part of the problem but I thought steel mounts should last better than this. They break, rip, tear and have been ripped right off the frame and its a bit unsettling. Only times we really go full throttle is startup and when we plow snow. Any ideas guys? We've tried steel, rubber etc.

 

[niky]

More mounts. Spread the load.

You're talking about engine mounts with steel inserts? I've never heard the like. Usually when we want something durable, we use polyurethane.

 

[Slash]

No, everything is steel, everything that we get in each set of 2. So you're suggesting that a polyurethane type of mount would be better? Can you explain how so? I kinda see where your going but I always figured steel would be better due to strength but is not the case I guess.

How durable are they? How reliable? Have you tried them and gotten good results?

Trying to replace them all the time gets old fast

 

[niky]

A solid mount will basically vibrate itself to death. Having an engine mount with a polyurethane insert, the poly absorbs some of the vibration and prevents breakage. Or should.

Most road cars use rubber. Race cars use poly to keep the engine hard-mounted without having massive vibration transfer to the frame.

Still vibrates horribly, though.

Need pics. Have no idea what your set-up is like, or how your engine is mounted. If you keep breaking mounts, there's some torsion on them that's causing them to break.

 

[Famine]

A solid mount will basically vibrate itself to death.

This. The engine is supposed to move (slightly) in relation to the car and the mounts are meant to dampen the movement. They need to be flexible or they will shear off.

As, it turns out, you've seen.

 

[Venari]

You can use one solid mount - generally on the 'tension' side of the torque reaction. Then use a rubber one on the 'compression' side. Then use a chain to stop the compression side ripping apart on torque reversals.

But these techniques are generally only used in the 500lbft-ish drag race spectrum. (more and you're looking at alternate mountings like sandwich plates across the whole front of the engine.) If you've just a stock engine, mildly tuned, you're better off with stock rubber or poly mounts.

Describe the engine, approximate output and what it's mounted into, I'll try to assist.

 

[Slash]

A solid mount will basically vibrate itself to death. Having an engine mount with a polyurethane insert, the poly absorbs some of the vibration and prevents breakage. Or should.

Most road cars use rubber. Race cars use poly to keep the engine hard-mounted without having massive vibration transfer to the frame.

Still vibrates horribly, though.

Need pics. Have no idea what your set-up is like, or how your engine is mounted. If you keep breaking mounts, there's some torsion on them that's causing them to break.

So I see the problem now, because it's solid the vibration causes them to weaken. I'll see about the pics, going to be a bit tough getting them.

This. The engine is supposed to move (slightly) in relation to the car and the mounts are meant to dampen the movement. They need to be flexible or they will shear off.

As, it turns out, you've seen.

Rev it and the whole truck moves from torque...engine stays put on the frame. Makes sense^^

You can use one solid mount - generally on the 'tension' side of the torque reaction. Then use a rubber one on the 'compression' side. Then use a chain to stop the compression side ripping apart on torque reversals.

But these techniques are generally only used in the 500lbft-ish drag race spectrum. (more and you're looking at alternate mountings like sandwich plates across the whole front of the engine.) If you've just a stock engine, mildly tuned, you're better off with stock rubber or poly mounts.

Describe the engine, approximate output and what it's mounted into, I'll try to assist.

At the wheels its putting out roughly 450 ft-lb torque and 400ish hp (I've been saying fwhp). Stroked 408, 400M crank, .30 out, rv cam etc. Old school build. Power is being made at about 2500-3000 rpm. Stump puller.

 

[Keef]

Part of your problem is that you've got this gnarly engine bolted to a really poorly designed ladder frame. The reason the engine keeps tearing the mounts off is not necessarily because solid mounts vibrate so much that they break but because the engine's torque flexes and twists the ladder frame until the mounts break. You need to find some way to reinforce the ladder frame where the drivetrain mounts to it so it won't flex.

Drag cars use roll cages and tubeframe chassis which are extremely rigid, and many amateur race cars use solid engine mounts with the car's factory unibody engine compartment, and obviously with full cages at higher levels for even more rigidity.

The problem isn't your engine or the solid mounts, it's the chassis. Ladder frames are not designed to be rigid, they're designed to flex and that's why they have exceptional load-bearing capacity that heavy-duty pickups and semi trucks need. As a matter of fact, semi trucks are a good example. They use very stiff engine mounts to support the immense weight of their engines which is quite obvious because when they start or shut down the entire tractor vibrates like it's falling apart. The trick is that the front part of the frame where the drivetrain mounts is heavily reinforced while the design becomes more flexible toward the hitch at the rear. This allows the forces of the engine's torque and the load at the rear to dissipate via twisting throughout the entire length of the chassis (also very visible when they pull away from a stop) as opposed to right at the engine mounts which is what yours is doing.

 

[Eric.]

I love when people quote their engine torque "at the wheels".

 

[Rotary Junkie]

At the wheels its putting out roughly 450 ft-lb torque and 400ish hp (I've been saying fwhp). Stroked 408, 400M crank, .30 out, rv cam etc. Old school build. Power is being made at about 2500-3000 rpm. Stump puller.

...

Even at 4500rpm for peak power, you'd be making more than 450 ft-lb if you're actually making 400hp.

You're not actually making 400hp. My bet is somewhere south of 350hp, at best, based on what I know of the build.

 

[Crash]

So I see the problem now, because it's solid the vibration causes them to weaken. I'll see about the pics, going to be a bit tough getting them.

It's not just that vibration causes your mounts to weaken, but it's also the impact load that the mounts receive when the engine moves as you apply power. Many steel does not have have a fatigue life if the forces on it stays within the elastic region and does not reach the yield point. It essentially is such that the mounts you have now is carrying a higher maximum impact force than it's designed to do, meaning you'll have to either add more engine mounts, use much stronger/thicker/bigger steel that can handle that impact load, or use another material that will dampen that impact load so it doesn't over-stress/over-strain the steel.

 

[Venari]

That's not too hopped up. I've a part-race spec 327 ready to go in a '62 Corvette and it should be pushing out more power than this (not more torque though!)

Stock or mild uprated engine mounts should do you. Any bent-crank V8 should be a smooth running unit, you shouldn't have too much vibration. If the whole truck is shaking after you've fitted stock mounts, something is out of balance. Is it engine, or roadspeed related? You may have a bad harmonic balancer - kits like this come in 28oz or 50oz balance - are you sure you've the right balancer?

Here's a good ref: http://www.coasthigh.com/v/vspfiles/28ozbalance.html

Hmm. If you're genuinely using a 'recycled' 400M crank, it's generally accepted they don't quite fit without machining the crank throws down. If this has been done, the whole lot WILL need balancing properly. If this hasn't been done, it will vibrate a lot.

 

[MaliciousMD]

Hmm. If you're genuinely using a 'recycled' 400M crank, it's generally accepted they don't quite fit without machining the crank throws down. If this has been done, the whole lot WILL need balancing properly. If this hasn't been done, it will vibrate a lot.

+1 to this. 400M crank to build a 408W is OLD SCHOOL. Grind the rod journals down, cut the counter weights down, machine the crank snout, heat treat since you ground the piss out of the rod journals, no thanks. That whole combo is like a balance guys dream and worst nightmare. Up charge for mallory, lost money because it took all day, LOL...

We use solid steel engine mounts for our engine dyno cart, never had a problem with cracking a mount even at 2000+ HP and 1500+ FT/LBS. Also have some polyurethane mounts for a few different engines, never had an issue with tearing one of those either.

You're not actually making 400hp. My bet is somewhere south of 350hp, at best, based on what I know of the build.

Not to be a dick but I'd be inclined to agree you're probably well south of 400/450 to the crank. Even if you were making 400/450, it wouldn't be enough to break a solid mount unless there is an underlying issue. I've driven plenty of cars and installed plenty of engines of varying power/torque levels with solid mounts without any issues. So you've been using solid engine mounts, what is your trans mount made of is my question...

For people wondering what a Windsor/Cleveland style motor mounts look like, they only bolt to the block at 2 points as seen below. Two wider mounting holes go to the block.

 

[Slash]

350hp won't spin all four 33s on dry pavement....and it does it with extreme ease. While I do see your points, my eyes don't lie lol. I know you'll all be like blah blah blah don't everyones eyes not lie and vids or bull. I don't own a camcorder and we don't even hardly let it run anymore. Now its not like they hold a burnout with 4.10 gears but I can get a couple feet with some smoke.

Yes its all balanced, notched the block etc. Current was built before aftermarket and we got the block for free. Weve built a few since but all our money goes to my moms med bills now.

I think Keef was right about the frame. It has split before on the passenger side but has been welded very strongly together if it has anything to do with it.


I say maybe 2 more years before we swap again, body work for now. 390 FE or 460 next, still undecided. 460 SVO, freakin' mad expensive aluminium block.

 

[Slash]

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