A-Body Body Mounts. Poly or Rubber, Or Both

[Pro-Tour Heavy Chevy]

I replaced the bodymounts about a year ago. I went with rubber as a compromise to gain a little isolation and comfort. I remember putting Poly's on my 68 A-body ,about 20 years ago, and they were hard as rocks and the car rode like crap and I felt every bump and vibration and they squeaked. I pulled the poly's out and put rubber in and called it a day and was happy with it.
Well now on the 71 and after only a year I noticed that the lower half of the rubber mounts are cracked and falling apart. The cushion between the frame looks fine, but the bottom half is shot.
I know the Poly will hold up, but are they still as hard as I remember.
I have a poly set on the way, so....

Should I change them out with all Poly
Return them and stick with the rubber..-or-
Use the lower half of the poly and replace the rotted rubber lower halves.

The rubber set was from OPGI
and the Poly's that are coming are energy's.
I don't recall the poly's I used on the 68.

When I had my 68 Nova I used Solid's w-frame connectors and it was fine. Just putting the polys on my 68 Chevelle and the results has me spooked.

[vintageracer]

I have always had A body convertibles and the poly body mounts make a huge difference in the solid feel of the car after installation. Less cowl shake. I have never experienced the harsh ride you describe following the installation of poly bushings. I also have never installed more than high quality lowering springs, GOOD shocks and brakes on these cars.

I can offer this suggestion that is poly related on the rear end of an A Body car with Urethane bushings installed in the suspension. Do not use Poly bushings on the upper eyes on the rear-end housing. Big mistake. Use rubber bushings there. Ride difference is huge just with that little change since poly bushings in that location will bind the suspension travel and result in a rough ride and other rear suspension issues.

Way back when 20 years ago in your 68 did you have poly bushings everywhere in the suspension and particularly in the upper eyes on the rear-end?

Something to consider!

[Hellbound]

can anyone tell me if it is possible to just remove the body mounts so it sets lower ? (dont care about the vibration have always had street legal chassis cars )

[Pro-Tour Heavy Chevy]

On the 68 the only the front suspension had Poly bushings. The rear was all OE rubber bushings with a stock sway bar. I remember that I bought the Bushings at the Pomona Swap Meet from a vendor who had assorted bushings Vacuum sealed to cards. The 71 has SC and C Stage 2 w-global west lowers. The rear has global west upper and lowers w-rubber bushings in the 3rd member with Helwig's Tubular sway bars. And I'm running Eibach springs w-Bilstien shocks.
The car rides nice and taught and handled the Angeles crest nice. I just don't want to repeat the past, it's just and the rubber ones are crap. I heard about 1 company making them in delrin, but they were only for Camaro.

[novaderrik]

get some solids to really tighten the car up, and tune out any undesirable harshness with softer springs and shocks.

[The WidowMaker]

can anyone tell me if it is possible to just remove the body mounts so it sets lower ? (dont care about the vibration have always had street legal chassis cars )

maybe. the bushings between the frame and body are not all the same height. if you removed the smallest ones, and subtracted that amount from the taller ones, you may be ok. you'll most likely end up with some fab work to make the 3/4" drop possible.

i cut mine and ended up with about 1/2" drop. the whole underside of my car has been worked over, so i didnt have to worry about clearance issues.

[HWYSTR]

get some solids to really tighten the car up, and tune out any undesirable harshness with softer springs and shocks.

What he said. It's the 'right' way to do it. Think about it, newer cars have perimeter frames, etc, and don't use 'bushings' to mount the body to the frame.


As for dropping the body to the frame, yeah, it can be done, BUT, the biggie is the crossmember fit. once you go beyond a certain drop, the area that's 'eyebrowed' to clear the exhaust won't fit anymore....


.

[ponchopwr70]

What about aluminum bushings? I have rubber in my car and I'm planning on changing to either poly or aluminum. I have a boxed chassis but I would think stiffing it up more is still good. Unibody cars that run connectors use aluminum so whats the difference with a full frame car? On a side note I can feel a little more vibrations in my s10 when I put poly body mounts. As far as my lemans goes I'm not looking for bmw ride quality just handleing.

[wmhjr]

What he said. It's the 'right' way to do it. Think about it, newer cars have perimeter frames, etc, and don't use 'bushings' to mount the body to the frame.


As for dropping the body to the frame, yeah, it can be done, BUT, the biggie is the crossmember fit. once you go beyond a certain drop, the area that's 'eyebrowed' to clear the exhaust won't fit anymore....


.

Be careful. I would not agree that it's the right way to do it. Newer cars have lots of things that older cars don't. You cannot just take one feature of a newer car, and assume it will be the best solution in an older car. The entire suspensions on newer cars are quite different, with far better geometry, system design, etc. Beyond that, new cars DO use isolation bushings to mount the body. Even a Mercedes SL600 uses them.

http://www.carpartsdiscount.com/auto/parts/mercedes_benz/sl600/body_mounts_bushings/years.html?3594=1930&price=2

One thing that you may experience is increased vibration and stress on body panel fitment, resulting in cracked seams, sealer and paint. If it's a race car - then no doubt solids are the best. If the car is street driven, solid body bushings can cause problems. There is a reason bushings were used. A great example is the bushings on the core support. I've personally seen solid mounted core supports destroy rads, and themselves because if you prevent any flex at all between body and frame, something HAS to give, and those body panels are not meant to do it. I used Poly, as personally I felt it was the best compromise between pure performance, ride and not destroying the body.

[jocko124]

where did you get your poly bushings Bill?

Sorry---did not mean to hijack the thread!

[wmhjr]

I got mine from Performance Year Pontiac. Part number was RPU270P. That was for my specific application. http://www.pysales.com/

[HWYSTR]

Be careful. I would not agree that it's the right way to do it. Newer cars have lots of things that older cars don't. You cannot just take one feature of a newer car, and assume it will be the best solution in an older car. The entire suspensions on newer cars are quite different, with far better geometry, system design, etc. Beyond that, new cars DO use isolation bushings to mount the body. Even a Mercedes SL600 uses them.

http://www.carpartsdiscount.com/auto/parts/mercedes_benz/sl600/body_mounts_bushings/years.html?3594=1930&price=2

One thing that you may experience is increased vibration and stress on body panel fitment, resulting in cracked seams, sealer and paint. If it's a race car - then no doubt solids are the best. If the car is street driven, solid body bushings can cause problems. There is a reason bushings were used. A great example is the bushings on the core support. I've personally seen solid mounted core supports destroy rads, and themselves because if you prevent any flex at all between body and frame, something HAS to give, and those body panels are not meant to do it. I used Poly, as personally I felt it was the best compromise between pure performance, ride and not destroying the body.

Never suggested using any one feature of a newer car or it being the best for older cars, mine was just an example. True, SOME newer cars have bushings, not all. Newer suspensions are not that drastically different, though do offer better geometry.

True too about added vibration and stress, that's a no-brainer, though as suggested that compensating with springs and shocks can just about null the effect. Longitude frame 'twist' is a concern with full-frame cars, regardless of the type of bushings, and even unibody cars suffer some. I've seen 2nd gen f-bodies' 1/4 panel-to-roof area crack on even low-perf daily drivers, though since it's well known, many brace for it when building. Radiators are in rubber isolators, or most are (Mopars are an exception), and there would have to be a ton of movement to damage one. Poly doesn't provide that much more give than solids, and can lead to the same problems in 'destroying the body'.

Anyway, on a 68-72 A-body, twist would be minimal with solid bushings, and the bumpers can be reinforced if it's a concern. (or add a cross brace at the front and rear most portions of the frame. And no, it doesn't have to give, like with my T/A, you can put a jack in front of or behind a tire and jack half the car up, it's that ridged. I compensated with springs & shocks, and not only does it handle good (over 1g easy), ride quality is about that of like a newer f-body. The give should come from the shocks and springs.

Not trying to be argumentative, just that I guess I'm on the other side of the fence. I had polys before I went solids, and prefer solids. Solids make suspension tuning more responsive, and you don't have to take into account any other movement.

.

[wmhjr]

Don't get me wrong - I'm not trying to be argumentative either. Just saying that solids are not necessarily the "right way" for a street car.

I have a 2 post lift. When I lift my '66 vert, you cannot open the doors. If you put a floor jack just behind the front drivers wheel and jack it up, you can visibly watch the door gap change as you raise the car. There is that much flex. It's not unique to just mine. That is EXTREMELY common. The same flex is happening on the road - especially if you're pushing the car. I completely agree that from a pure performance perspective, solids may be the way to go. I just know that especially in these older cars, there is a TON of flex that can happen, and solids will put that flex directly into the body panels. If it's a race car, then who cares. But if somebody spent a good deal of time finishing the car, solids may easily destroy an otherwise great body and paint job. Poly bushings are quite a bit more rigid, but they DO give at least a little. Suspension can't really tune out the effect of the solid concerning what we're talking about because dampened coil springs can't prevent shock/vibration from being transmitted to the frame pockets unless you make the suspension so soft that you lose any advantage that solid mounts might gain. Rubber mounted rads are the most common (though that's not what I have) but even they can only be isolated so much.

Not arguing with you - I pretty much agree. I just wouldn't want to see somebody get waves in their rear quarters unexpectedly and I've seen that happen.

[ponchopwr70]

hwystr what are you running for bushings? I love the lemans btw.

[Hellbound]

The motor an trans will be solid mounted also i like to see an feel the car shake ! any any fab work is never enough thats what i love to do !