[15bhardwick]

Been searching and seeing guys using elephant ears and other motor/mid plates on their setups and wondered if I should be doing the same

Current setup is 3450 lb gto. Footbrake only. Guessing right around 500hp. Solid motor mounts and Poly trans mount.

Heard guys cracking blocks because of the stress from the solid motor mounts. Headers I have now eliminate the possibility of a mid plate.

The elephant ears look like they would be easy enough to make but do I need it for this combo?

In future car will have a mid plate at the least

[70 bird]

I've been running solid mounts and a poly trans mount for 15 years without issue. 462 with 15psi streetcar no trans brake. fwiw.

[25stevem]

At the 500 hp level your good, but once you get 600 you want the mid plate just for the sake of better and more consistent 60 ft times no less releasing the block side walls from the stress of being part of the frame.

[Dragncar]

Stay away from solid mounts. I run elephant ears ans Mighty Mounts. ^0 foot in the low 1.4s
But now and going with a mid plate with the rest of my stuff.

[Old Goat Racer]

1 solid mount, neoprene tranny mount, foot brake, close to 600 hp. 10 years.
Car # 316

[hojs69]

Solid motor, poly trans also, for a few decades now. No issues.

PS: To be complete, I did run a solid trans mount for a few passes only. Shredded the trans case. Lessons of youth!

[VCho455]

One has to look at the whole picture. A foot braked 500 hp on street tires or small slicks vehicle isn't likely to cause the frame to twist significantly. So solid mounts even with a poly transmission mount isn't likely to cause a transmission or engine to crack. But if (or when) you start launching harder and twisting the frame more then that twisting motion is transferred to the engine and transmission. Enough of a twist and something breaks. Looking at video footage can give you insight into how much twisting your experiencing.

I pulled the left front wheel off the ground in my GTO for years (It was my daily driver and I chased points at PIR) and that was cool until the left rear lower control arm mount broke off the frame. Suddenly I had new insights as to where I needed to look for problems.

At the time I was running solid mounts and a stock transmission mount. I regularly inspected the transmission mount for failure. My thinking was that the rear of the engine and transmission could move around some and prevent any breakage around the front mounts.

Just my opinions.

[PAUL K]

We've always run a solid mount on the left side, GM on the right and poly trans mount. A lot of passes between the 700 hp-1100 hp range and never had an issue. This is with the three bolt design motor mounts. My brother has a torque strap on his.... I don't.

[Old Goat Racer]

Less than 500 HP. 10.90 @ 121 mph. Same mounts as described in my previous post.

[AG]

Originally Posted by Old Goat Racer

1 solid mount, neoprene tranny mount, foot brake, close to 600 hp. 10 years.
Car # 316

That car must have more than 600 Hp to pull that number unless it weighs 2800 lb. That's a great 60'. Is it a '70 GTO?

[Tom Vaught]

Many, Many Years ago I had a stock engine mount system on my GTO.

Then the Chebby Boys started having issues with the driver's side mount failing under
acceleration and binding the throttle. Most of these cars were solid rod systems from the firewall to the carb linkage. A few were involved in accidents.

Even though I had Cable Linkage I still installed a chain between the frame and the drivers side head. Safe vs sorry. Worked fine but on some cars it made noise.
With the Smitty Steel Pack Mufflers you did not need to worry about some "Chain noise".

Years later I removed the chain and installed a 1/8th inch thick, 1 inch wide strap that went to the attachment points. NO RATTLE. The strap had a milled 1/8" clearance so the engine could move slightly and not bind anywhere the factory mounts. Has worked great for many years. This mod also took the load off the left side of the block under acceleration. Happy happy.

So solid mounts might work great on a roof car but I thought my CONVERTIBLE could use a bit more safety in the way the engine was located when under power.
It is not a 10 point chassis car but the mod will work on a street driven quarter mile track car.

Tom V.

[Formulajones]

I run a solid mount on the driver side, stock rubber on the passenger side, and a poly trans mount.

Been doing that for decades, up to 700hp street cars and even stick shift cars at the track. Never an issue.

[Sirrotica]

Some good information about stock blocks and using solid motor mounts. There are at least 2 people that posted that attributed their #2-3 main failures to block distortion, and using stock style mounts.

http://forums.maxperformanceinc.com/...t=motor+mounts

Some don't realize that Pontiacs original 2 bolt mounts (59-69) were putting tension on only the #3 main web. Using that location is going to stress one portion of the block with that mount system. Remember that the original Stratosteak V8 displaced only 287 cubic inches, the displacement leap frogged up to 455 cubic inches in 1970, along with a much longer stroke that produced much more torque than the 1955 engine did.

In 1970 Pontiac re-deigned the mount placement to straddle the #2 and #3 main bulkhead plus added stiffening ribs on the outside of the block. All the 455 applications used the later style mount system, shown that the A bodies had one set of mounts for the 400 and less cars, and a separate mount system with the 3 hole setup on the A bodies with 455 engines through 72, the G bodies got a new 3 mount system in 1970 that they used in all engines.

Pontiac evidently was worried that the early system was putting too much stress on the #3 main with the longer stroke 455 engine. Afterall they had a 2 bolt system for 15 years, and completely redesigned it to use 2 main bulkheads too disperse the stress over a wider area. If you look at the bottom of a 5 bolt 70-76 block it's easy to see the change, and why it was done, just remember if you're using the early 2 bolt mounts, the stress is being concentrated on only 1 bulkhead. Using the later style system (3 bolts) is probably why some have gotten away with using a left hand solid mount with a standard right mount. The attachment points of the later mount are a much better design to spread out the loading of the stock block.


Pontiac engineers saw the long stroke 455 engines were going to put too much stress on a small portion of the block, and cause distortion. A strong running 455 will destroy the left stock type mount in a short time if not restrained with some other means. Even the captured mounts, the rubber gets worn out quickly. One poster in the thread referenced, tore a mity mount in two on his first pass on a drag strip.

I personally keep both stock mounts, and restrain the engine with a turnbuckle on the left side. The further away from the crankshaft centerline the restraint system is, the more leverage it has to stop unwanted movement. The stress is further spread and uses the water crossover as well as he intake manifold to tie to the right bank. It worked flawlessly in my race cars, using the 2 hole system with new mounts they would rip apart in 2-3 weeks. After affixing a turnbuckle I used the mounts for 3 years, and when I removed the engine, the left mount looked like new.

[Tom Vaught]

Originally Posted by Sirrotica

Some good information about stock blocks and using solid motor mounts. There are at least 2 people that posted that attributed their #2-3 main failures to block distortion, and using stock style mounts.

http://forums.maxperformanceinc.com/...t=motor+mounts

Some don't realize that Pontiacs original 2 bolt mounts (59-69) were putting tension on only the #3 main web. Using that location is going to stress one portion of the block with that mount system. Remember that the original Stratosteak V8 displaced only 287 cubic inches, the displacement leap frogged up to 455 cubic inches in 1970, along with a much longer stroke that produced much more torque than the 1955 engine did.

In 1970 Pontiac re-deigned the mount placement to straddle the #2 and #3 main bulkhead plus added stiffening ribs on the outside of the block. All the 455 applications used the later style mount system, shown that the A bodies had one set of mounts for the 400 and less cars, and a separate mount system with the 3 hole setup on the A bodies with 455 engines through 72, the G bodies got a new 3 mount system in 1970 that they used in all engines.

Pontiac evidently was worried that the early system was putting too much stress on the #3 main with the longer stroke 455 engine. Afterall they had a 2 bolt system for 15 years, and completely redesigned it to use 2 main bulkheads too disperse the stress over a wider area. If you look at the bottom of a 5 bolt 70-76 block it's easy to see the change, and why it was done, just remember if you're using the early 2 bolt mounts, the stress is being concentrated on only 1 bulkhead. Using the later style system (3 bolts) is probably why some have gotten away with using a left hand solid mount with a standard right mount. The attachment points of the later mount are a much better design to spread out the loading of the stock block.


Pontiac engineers saw the long stroke 455 engines were going to put too much stress on a small portion of the block, and cause distortion. A strong running 455 will destroy the left stock type mount in a short time if not restrained with some other means. Even the captured mounts, the rubber gets worn out quickly. One poster in the thread referenced, tore a mity mount in two on his first pass on a drag strip.

I personally keep both stock mounts, and restrain the engine with a turnbuckle on the left side. The further away from the crankshaft centerline the restraint system is, the more leverage it has to stop unwanted movement. The stress is further spread and uses the water crossover as well as he intake manifold to tie to the right bank. It worked flawlessly in my race cars, using the 2 hole system with new mounts they would rip apart in 2-3 weeks. After affixing a turnbuckle I used the mounts for 3 years, and when I removed the engine, the left mount looked like new.

Great Post, Turn buckle, chain or strap. Solid Motor mounts can cause block failure in the area you mentioned if you are making any horsepower over time.
That is also why I use a similar type device as your Turn-buckle and stock motor mounts.
I believed you when you posted your info some years ago and I agreed with now.

Tom V.

[Old Goat Racer]

Originally Posted by AG

That car must have more than 600 Hp to pull that number unless it weighs 2800 lb. That's a great 60'. Is it a '70 GTO?

How did you guess ?
It's a 72 Le Mans with a 70 GTO fiberglass front end, trunk lid and rear bumper
Lexan windshield, rear glass and quarter windows. Door braces removed. Dash removed and refabbed. 4.11 gears. Car has a trans brake but this "old schooler" likes to foot brake. 10.5 Radial slicks. Car and driver about 3125 # .
It is what it is !

[AG]

Originally Posted by Old Goat Racer

How did you guess ?
It's a 72 Le Mans with a 70 GTO fiberglass front end, trunk lid and rear bumper
Lexan windshield, rear glass and quarter windows. Door braces removed. Dash removed and refabbed. 4.11 gears. Car has a trans brake but this "old schooler" likes to foot brake. 10.5 Radial slicks. Car and driver about 3125 # .
It is what it is !

That's a badass car. Hp formula says you should be 10.10 so you got that dialed in.

[Mike S]

I have used solid motor mounts on the car since 2001. Never had a problem till I started using the trans brake. I crack no. 3 main right in the middle of the block. At the time I had the 2-step set at 2400. Don't know if that was throwing vibrations into the block or not. I installed elephant ears and raised 2-step up to 3800 and haven't had a problem in 12 years.
Mabey one day I might install a motor plate but when something is working I tend to leave it alone.

[Tom Vaught]

Originally Posted by Mike S

I have used solid motor mounts on the car since 2001. Never had a problem till I started using the trans brake. I crack no. 3 main right in the middle of the block. At the time I had the 2-step set at 2400. Don't know if that was throwing vibrations into the block or not. I installed elephant ears and raised 2-step up to 3800 and haven't had a problem in 12 years.
Mabey one day I might install a motor plate but when something is working I tend to leave it alone.

Well you make #5 of the people I have spoken with over the years that have cracked the no.3 main in that "middle of the block" location.
They also ran trans brakes.

A combination of things related to those inputs.

Tom V.

[Dragncar]

The reason I do not run them is Dan Whimore told me they have problems when running a T brake cracking blocks. Good enough for me.
I had a problem when I was experimenting with different intakes and with one intake-spacer combo the throttle cable was on the tight side. Usable I thought until at the track I put the car in gear with a fast idle and with Mighty Mounts the engine moved enough to give it gas and the car went forward about 6-8 feet. Got lucky no one was hurt.
I put elephant ears on after that then went to T brake.
Might Mounts flex more than factory. I had these big car motor mounts, 5 bolt off of a station wagon and they moved less than Mighty Mounts.

[Mr Anonymous]

this works.