What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Poly vs rubber engine mounts

I think no--all Chevy engines I've messed with (pre-1986) have 3 bolt holes in the block,for the motor mount steel bracket to bolt to--or the mounts like in your lower photo,used on 1970 or so and older vehicles..

They are referring to the "shell" that surrounds the rubber insert when they ask 3 or 4 bolts or rivets are holding them together on the clam shell type motor mounts used after 1973 or so..
 
if you offroad skip the clamshell design. I was able to rip the poly inserts in a short amount of time.
 
You're saying that frame flex kills them faster than just holding the engine torque. I suppose the more rigid you make the mounts (like ORD-style), the engine is almost becoming another crossmember.
 
I just yanked the engine outta my Suburban. I was planning on throwing some new cheapie mounts under there because the old ones are old. But I had not heard the horror stories about dirt cheap mounts. These ones still look alright (though old), but the 30-year-old mounts in the K10 gave up the ghost after last year's trail runs.

Do we know how well things worked out for @twoslo4five0?
 
campfire said:
Do we know how well things worked out for @twoslo4five0?
Click to expand...

I think I know why his rubber mounts last so long.....He only went wheeling in it twice and it's been sitting in pieces ever since while he started and never finished two other rigs.:D

Back on subject....I had to replace my poly motor mounts this year. They were in there since about 2000. When I broke the trans in two, I figured I should go ahead and replace the motor mounts too. They looked fine but after I replaced them, the motor sat an inch or two higher.
So they don't last forever.....But 17 years is a good run.
 
sheeze... I guess I should look at the mounts on my 78 chevy???? never replaced motor mounts or trans/xfer mounts
 
I'm running the 3.116G, and I've not had problems yet.

Although I did notice that the through bolt (long one that holds the motor "hat" to the motor mount) broke on mine this trip last week. Not sure why, but I'm not going to blame the poly mounts. Seems a one-off problem.
 
FOR MUD said:
I think I know why his rubber mounts last so long.....He only went wheeling in it twice and it's been sitting in pieces ever since while he started and never finished two other rigs.:D

Back on subject....I had to replace my poly motor mounts this year. They were in there since about 2000. When I broke the trans in two, I figured I should go ahead and replace the motor mounts too. They looked fine but after I replaced them, the motor sat an inch or two higher.
So they don't last forever.....But 17 years is a good run.
Click to expand...
17 years and at least one roll over if I recall correctly :whistle:.
 
I also noticed that the rubber mounts seem to degrade fast with heat. After I put headers on I changed the mounts and 3 months of easy street miles later both had deteriorated. The Energy inserts have been holding up well. A little vibration at idle, but it's a truck, not a Lexus.
 
Can't see why I had problems with these... they were brand new just 33 years ago.

20171114_184432.jpg
 
Some say Poly gives more vibration than rubber, but I can tell you that poly is way smoother than the brackets sitting on the frame. Engine is a good 1/2" higher, too. 2 tips on the install:
  • Look at how the old insert is oriented. It will fit fine in the clamshell backwards, but won't fit on the engine bracket correctly that way.
  • The first through-bolt is easy to align. Once that's in and all clamshell bolts are started, put a jack between the frame and engine on the other side to coerce a little more space. When the engine drops into place, the little ears on the insert align with the engine bracket and the through-bolt can go right in.
 
Blue85 said:
Some say Poly gives more vibration than rubber, but I can tell you that poly is way smoother than the brackets sitting on the frame. Engine is a good 1/2" higher, too. 2 tips on the install:
  • Look at how the old insert is oriented. It will fit fine in the clamshell backwards, but won't fit on the engine bracket correctly that way.
  • The first through-bolt is easy to align. Once that's in and all clamshell bolts are started, put a jack between the frame and engine on the other side to coerce a little more space. When the engine drops into place, the little ears on the insert align with the engine bracket and the through-bolt can go right in.
Click to expand...

Luke, what are you running as a tranny mount?
 
I don't remember any vibrations from the blown out tranny mount, just a clunk as the transmission reversed, but it's been more than a decade. The blown engine mounts were most annoying with the truck stopped, in Drive. I was getting some driveline vibe at freeway speed, but it was less noticeable than the Swampers. It hasn't seen those speeds with new poly mounts yet. From everything I read, the danger was in making the transmission mount stiffer than the motor mounts - it puts stress into the transmission / T-case housings. Stiffer on the engine is supposed to be safe.
 
In reality a poly tranny mount won't break a bell housing with GOOD rubber engine mounts. They don't flex that much when in good shape. But worn ones would be a recipe for disaster quickly because they would allow more than enough slop from the engine jumping around.

Poly is super convenient because they most likely will never need replaced, and won't kill a day at the trails.
 
You must log in or register to reply here.

Latest Posts

Top Bottom