Which year front lower a-arms have round holes instead of oval? My 72 Supreme has the one oval bushing hole on each side.

I was considering trying out the G/W del-a-lum bushings for the front control arms, but they require the round hole lower arms.

 

btt

 

What is the purpose of the oval bushing?

 

I can't give a high-quality, Olds-centered response here, but in Ch@^ys, the oval bushings were used in heavy duty applications, such as station wagons, El Caminos, and Chevelle SS's (and presumably in Olds in the various W-cars, though I will admit I am not knowledgeable about their intricacies).

All other Chevelles will have round ones, and I would suspect other light-duty applications, such as 6-cyl. and 326 LeMans, and 350 Skylarks would too.

- Eric

 

Not sure if thats the case with olds. I had a 71 442 oval. And a 72 S also oval.

 

My 72 has the one round, one oval on each arm.
I had heard rumors that this change ~might~ mave been made mid year, so some 72's could have all round, too.
When i ordered my new Moog bushings, they sent one round, one oval per box, so maybe the majority had oval...
I would like to know more about this myself...

 

As I understand it, take it FWIW, earlier cars had the round bushings, say pre 69. Somewhere around 70/71, performance suspension equipped models got the round bushings (less deflection due to smaller bushing) & the run o' mill cars started to get oval bushings to make the suspension more compliant, ie a little softer w/ less transmission of harshness. Not putting this out there as gospel but that was my understanding.

The GW Del a Lum bushings are awesome IMO & you can send the arms to them to be modified so they will accept that bushing. I don't know exactly what they do, but it adapts the oval arm for a round Del a Lum bshg. At that point I don't know if you might be just as well off buying the complete arms unless you are trying to keep stock look.

 

This is correct. In 1969 all GM A-Body cars had round bushings front and back. In 1970 GM went to the oval to smooth the ride. In the case of the Chevelle SS, it kept the round bushings through 1972 while the Malibu went oval. On the Chevelle it is a great clone ID.
442 owners may want to weigh in but it is quite possible that Olds put the oval in all of thier cars as they were the most luxurious of the line.

 

X3. It turns out that ride harshness in part comes from the fact that when you hit a bump, the wheel wants to move REARWARD as well as up. Round bushings constrain this rearward motion and thus transmit more of the bump to the passengers. The oval bushing allowed some rearward motion, smoothing the ride but adding unwanted suspension motion in the process. Suspension design is a tradeoff. Metal bearings with zero compliance give the best handling and the worst ride. The converse is also true.

 

Okay, I stand corrected.

I could have SWORN that my documented, original Chevelle SS had 2 oval bushings when I took it apart in 1981, but I guess thirty years is a long time and memory plays tricks.

I found a GM quote from 1970:
"The new oval-shaped lower control arm rear bushing for Chevelle models (except SS 396) contributes to a smoother, quieter ride."

So I guess that makes sense.

- Eric

 

I should have said it is something to look for when trying to ID an SS. To take it further... From what I have read, on the assembly line the guys grabbed what was available. Part shortages also may have played a role. Also it is possible that they were replaced because of an accident. The GM replacement parts were all oval bushings.

 

I probably remembered it backwards.

One rear bushing was completely trashed (no rubber left, and the surrounding part of the A-arm was bent up), so I had to get one from a junk yard. They only had one type - I thought it was only rounds, but maybe it was only ovals.
Either way, I ended up with one of each, and had to buy extra parts, as the auto parts store only sold them in pairs.

Now I've got to crawl under there and look for myself.

I guess the memory goes first...

- Eric

 

I worked at the Framingham BOP plant in 1972, and the parts that went on the line were approved by production engineering. If a part was substituted, it had to have a TMD (Temporary Manufacturing Deviation) to get it into a car.

The notion of grabbing any part is a urban legend.....

The process that GM had was pretty good, and except for the quanity over quality part.

 

How awesome to have worked the line in the days of the muscle car.

I am sure that there were strict controls. I imagine if there was a shortage of one style, production engineering would approve the alternate before shutting down the line.

 

In the Chevys the round bushing were designated for BIG BLOCK cars and the Oval for small block cars. I have parted out and restored many Monte Carlos and Chevelles. THIS info IS very consistent on the chevy control arms. NOW also remember that alot of these cars are 40+ years old and some have had partial resto and maybe even in accidents years ago...so parts get swapped and things get changed.

SO you might want to check to see if the cubic inch of the motor and or performance might be the reason your Olds received oval or Round bushings...I can almost bet that power and or engine option will be some of the reasoning behind the ROUND or OVAL bushings were used.

Jim
J D Race & Resto