Poly Engine Mounts

[bari]

Is it worthwhile putting on the poly engine mounts from either VB&P or Eckler's? Have a ZZ4 engine and I remember Corvette Mike's replacing one original mount. The other one is still the stock one that I had for the '75. Haven't driven the car since I brought it back from the shop last year and now it's still at a local mechanic's for more mods. I'm assuming there's only two of these engine mounts on the C3, right?

Eckler's pricing is cheaper by about $20 vs VB&P??? ($39+ vs $59+)

Thanks for any feedback.

 

[1BAD80]

Yes they are good. they take away more vidration, don's rot like the older ones. You can get them from any catalog auto parts Jegs, Summitt and many more.
I bought mine from VP&B along with the chassis system. Try a search on this site.
While your at it , I would recommending replacing the trans mount.

 

[bossvette]

I have polygraphite everywhere but the Diff. bought from PST, but they are redily availabe most everywhere.

 

[clar2001]

Whats even more important than poly is safty mounts, if they break they have a lock so the engine won't flip up thure the hood.

 

[1BAD80]

I agree on the safety lock type. That's why the ones from VP&B are a higher price, their that type.
On 80-82 its best to use the poly mounts on the rear end on the front differential mounting bushing, and the front sway bar. Poly mounts make all the difference to the performance of the car, any place you can put them its worth the little extra price, I have never had one go bad since they come out. They really help the improvement of any ride.
Good Luck,
George

 

[MrGibbly]

I just replaced my old cracked original mounts on my '78 with Energy Suspension Urethane, Zinc Coated Engine Mounts # 3.1114G from Alamo Performance. They have reduced the vibration transmitted to the frame perceptably until I put the car in gear. I highly recommend these mounts. Later this week my poly tranny mount and suspension kit come in so I'll let you know how that goes. The only problem I had with the installation was that since my tranny mount is broken as well as the motor mounts the entire assembly had shifted back about 1/8". I fought with the thing for 6 hours trying to shift everything forward enough so that the bolt holes in the engine block would line up correctly with the motor mounts. I think next time I'll do the tranny mount first...

 

[1BAD80]

Try putting a floor jack under the Trans/motor and take some weight pressure off and you should be able to move it a little easier. You will be very happy with the new mounts, the rear differential mounts are VERY importain if your making any type of power to keep the rearend shock away from the mounting surfaces, this is the problem on pre '80 with the old style mounting brace.

 

[Hib Halverson]

The only practical advantage of polyurethane engine mounts is they often have better durability than OE rubber mounts.

Other than that, there is no advantage to them on the street. They increase vibration transmitted to the vehicle structure and interior.

The real advantage to poly engine mounts is they gave the manufacturers of urethane parts another application for which to sell their products.

 

[1BAD80]

The only practical advantage of polyurethane engine mounts is they often have better durability than OE rubber mounts.

Other than that, there is no advantage to them on the street. They increase vibration transmitted to the vehicle structure and interior.

The real advantage to poly engine mounts is they gave the manufacturers of urethane parts another application for which to sell their products.

Sorry I fully disagree with most of the posting from Hib Halverson.
I have worked in a testing lab & building test machines.
Urethane bushing help eliminate vibration and less movement giving more faster action to some parts.
It depends on the application. I have been using urethane products since the mid 70s and no problem with them.
I have LESS vibration transmitted to the vehicle structure and interior. I also have solid motor mounts on my small block 427 motor. There is VERY LITTLE vibration on the car since I have ALL urethane bushings, mounts, where ever I could put them. It takes the shock better, and gives faster response to the steering when the sway bar and other components on the front end use urethane bushings. The use of them on the rear end pre '80s can help stop the breaking of the rearend housing, it helps stop the movement of the brace's, and rear spring mounting surfaces from breaking. Plus they last twice as long as a regular rubber type.
This is my $ .03 worth.

 

[Hib Halverson]

Sorry I fully disagree with most of the posting from Hib Halverson.
I have worked in a testing lab & building test machines.
Urethane bushing help eliminate vibration and less movement giving more faster action to some parts.
It depends on the application. I have been using urethane products since the mid 70s and no problem with them.
I have LESS vibration transmitted to the vehicle structure and interior.

If you work in a lab, you must have test data. Please post the test results you have supporting your claim of less vibration transmitted to chassis the via polyurethane engine mounts than with O.E. rubber mounts.

I have LESS vibration transmitted to the vehicle structure and interior. I also have solid motor mounts on my small block 427 motor. There is VERY LITTLE vibration on the car since I have ALL urethane bushings, mounts, where ever I could put them.

I just want to get this straight: you, a former test technician, are saying that replacing a rubber (or urethane for that matter) engine mount with a steel mount will transmit less vibration and noise?

Again, how about posting some test data to back up that statement. I ask for that only because even the manufacturers of soild engine mounts do not recommend them for street use because of the engine vibration and noise they transmit to the chassis.

Also, let me ask one small final question. If polyurethane powertrain mounts and suspension parts transmit less vibration, considering they do last longer; why don't car companies use them for isolation in O.E. applications rather than rubber?

 

[Robin7TFour]

has anyone had any problems aligning the diff mount poly bushing? anything special for setting the proper angle etc


robin

 

[Jack]

No test data here ... but I'm running ES trans & motor mounts in my 71. I like em & recommend em. Chances are your old mounts are mushy/rotten ... replace em with something ... I prefer poly.
JACK:gap

 

[bossvette]

the local Vette shop recommended stock bushings for the diff and thats the way I went. Poly everywhere else though. He said the poly was too stiff for the diff I took his advise. Have not broken a rear yet, but did snap a stock spindle and replaced both with aftermarket hardened ones. I guess its a matter of opinion.


Craig sr.

 

[1BAD80]

IM talking about a regular Vette with more than average HP. Urethane is the only way to go an any type of car or truck.


To Mr. Hib Halverson
I was explaining what I had to USE ON MY CAR for motor mounts.
I have a little more than average horse power with a small block 427 motor, there is not that much vibration since the motor is balanced very well, its the torque of the motor that break's the motor mount's NOT the vibration, it only shakes the whole car because of the cam.

The auto companies would put them on all their cars and trucks then the cost would go up, and not everyone has a sports car that need them. They make them for around a 10 year life or what ever the spec is.

Your quote: Other than that, there is no advantage to them on the street. They increase vibration transmitted to the vehicle structure and interior.

No they don't increase, they help decrease vibration and with less squash out for a better control on handling and performance.

For facts ask anyone that has them.
Or you could write VP&B for the data.

George

 

[Hib Halverson]

To Mr. Hib Halverson

You can call me "Hib"

For facts ask anyone that has them.
Or you could write VP&B for the data.

Ok...I guess I should establish credibility.

I've worked on and raced Corvettes for 35 years. I've worked on C1s, 2s, 3s, 4s and 5s and I currently work on C3, 4 and 5 on a regular basis. I own an maintain a C3 and a C4. I've been an automotive technical writer since 1984 and have done technical work for most of the Corvette magazines that circulate nationally. In the past, on a contract basis, I've done product developoment work for aftermarket companies. I'm a former service technician. I've got a degree in automotive service technology. I belong to the Society of Automotive Engineers. I've keep factory service manuals on file for 63, 65, 71 and 82-03. I've worked with polyeurthane suspension parts amost since the stuff was first introduced in the late 1970s. Generally my work has been with either Energy Suspension or Vette Brakes and Products. I've worked with urethane powertrain mounting pieces for about as long as they've been available. I don't need to write VB&P for information because I talk to their engineering people on the phone regularly.

Now...here are the facts.

1) Polyurethane has a much higher durometer than rubber, thus it's stiffer by a significant measure.

2) The purpose of flexible powertrain mounts is to damp engine noise and vibration. Use a powertrain mount material that is stiffer than rubber and more noise and vibration will transfer from the engine to the chassis and, then, to the interior because the stiffer material provides a lower level of damping.

3) Polyurethane is more durable than rubber but polyurethane powertrain mounts, as long as they are the "safety mount" design are no more reliable than rubber mounts because both designs use bonded construction where the rubber or urethane is bonded to the metal.

I was explaining what I had to USE ON MY CAR for motor mounts.
I have a little more than average horse power with a small block 427 motor, there is not that much vibration since the motor is balanced very well, its the torque of the motor that break's the motor mount's NOT the vibration, it only shakes the whole car because of the cam.

My C4 has a 460cuin BBC (535hp/530lbs/ft) with all the good stuff--forged crank, Crower rods, 9.75:1 BME pistons, Crane mechanical roller, ported/polished oval ports with L88 valves, roller rockers, Edelbrock performer, Holley 850, headers, MSD ign. and other go-fast stuff.

But...it uses stock GM rubber engine mounts. The car has well over 100 passes on it and they've yet to break. My engine, in spite of it's radical, roller cam does not shake the whole car because I have rubber engine mounts to damp a lot of shaking caused by the cam's rough idle.

Bottom line. Polyurethane engine mounts are more durable than rubber in many cases. Urethane powertrain mounts will reduce engine movement due to torque reaction or misfire and will transfer more of that movement to the chassis. There is no improvment in engine performance nor is there an improvement in the car's handling from installing polyurethane powertrain mounts. Iif you decide to install them, understand that there will be an increase in noise and vibration from the engine to the chassis and then to the interior.

 

[1BAD80]

Quote: nor is there an improvement in the car's handling from installing polyurethane powertrain mounts. Iif you decide to install them, understand that there will be an increase in noise and vibration from the engine to the chassis and then to the interior.

I guess I should establish credibility, I feel that it is not necessary to do, as I do not have to impress anyone.
But just for you Hib, I have a Journeymans card for Heavy duty master truck gas & diesel. Journey Machine builder, I have built testing machines for industry and assembly lines, and tested the durometers of different silicone and urethanes. Im a Mechanical Engineer, and a member of the club also. I trouble shoot for one of the big 3 Engineering platforms. Trained from Motrola Fundimentals of Nosie, and worked on squeek and rattle problems for dealers, and assembly plants, doing audits on them.
I have built numerious motors and cars. I have built and pit crew on a alcohol dragster A/Fuel nitromethane injected.
Now I have read thru VP&B catalog and they state more than once their products reduce noise and give better handling. This can be read by anyone and let them decide. I am not trying to put you down or anything else. The proof is in the reading of the catalog.
I race my car also, I have run 10.80s with my Vette.
9.20s on my Harley drag bike that I built. Thats all I want to say, about $.05 worth.
I will not respond to this posting again as I feel the question has been answered.
Good Day,
George

 

[Jack]

ROB (admin):
Sadly ... this particular thread seems to have acquired a CF-like aroma.
JACK:gap

 

[Hib Halverson]

I've been a user of what Vette Brakes and Products sells for many years. I've, also, used urethane parts from other companies, such as Energy Suspension. While both of those manufacturers sell quality products, I would suggest that their catalogs not be relied upon as a sole source of information about the results of using polyurethane parts in powertrain mounting or suspension applications. Catalogs exist mainly to market and advertise products so, in some cases, you must keep-in-mind with what perspective the facts in those catalogs are offered.

Originally this thread was about polyurethane engine mounts--I call them "powertrain mounts" sometimes--however, handling has been brought into the debate, perhaps as a way of bolstering an opinion.

If we're going to talk about the handling attributes of polyurethane parts then we need to switch and talk about suspension bushings and mounts rather than powertrain mounts because, at least with the C3 Corvette, engine mounts have little to do with handling.

In most cases where they are used in C3s, stiffer suspension bushings, spring mounts, trailing arm bushings, strut rod bushings, stabilizer bar mounts and stab. bar links can improve (and in a few cases, improve significantly) the way a car corners.

In both cases, powertrain mounts and suspension parts, use of polyurethane increases noise and vibration (in the case of powertrain mounts it's engine noise and vibration. In the case of suspension pieces, it's road noise and vibration) transmistted to the chassis and then to the interior.

Lastly, the fact that urethane transmits more noise and vibes to the interior does not mean use of it is intrinsically a bad thing. It just means, like many cases of aftermarket modifications, there might be some trade offs. Yeah, you might want the better durability and the less engine movement a urethane powertrain mount can provide, but it'll come with you feeling more engine noise and vibration.

You might want the lower level of compliance and better "camber stiffness" front control arm bushings made of urethane will provide to your front suspension, but that'll come with increased road noise and vibration transmitted to the interior and the car will ride a little more harshly.

 

[mrvette]

I remember trying a polyurethane prophylactic once....

but she claimed the ride was to hard.....



GENE