I plan to add a rear sway bar to my 72 convertible. The front sway bar is 7/8ths in diameter. Should I match the rear sway bar to the same diameter as the front or can I go with a 1 inch. The Parts Place has kits that include the boxed control arms, shims and bolts but only for 1 inch bars. I think that if I want to use a 7/8ths, I would have to buy the parts seperately.

 

The 70-72 442s came with 15/16ths front bars and 7/8 rear bars. You could probably find good used bars here and buy the boxing strap kits (cheap..around $25 for the boxing straps) and have them welded onto your existing rear arms (that's all the factory did).

Bolts/nuts are simple...get Grade 5 or 8 locally.

Get new bushings pressed into your rear arms also (again...you can order the bushings locally).

 

The parts book says it should have a one inch front bar and a .875 (7/8") rear?
Maybe you both measured a little off?
The book could never be wrong?
Whatever it is I just know that the front bar should always be larger than the rear.
Don't forget that you need the sway bar shims too.

I plan on doing the same, the Chebelle place has the boxing plate kits for a good price and the bars are around used and new.
I think all the GM A bodies used the same bar IIRC, excepting cop/heavy duty stuff maybe.
A guy on another site said his welder dude told him that you couldn't weld those plates in with the bushings installed or it will burn up the rubber?
I'm no welder, and not trying to hijack the thread, but does anybody know if that's true?
I would hate to have to remove my new bushings to have those plates welded on.

 

Either I must have measured wrong or my math is not as good as I thought. I measured the front at .960. My guess was 7/8ths because the measurement was short of 1.000. Maybe accurate measurements were'nt that critical 38 years ago. I think I'll try the ol adjustable wrench measuring trick.

 

My front bar is a hair less than 1.0", too. The vert got this size as standard.

The rear bar was only 7/8" from the factory in this year. Only the 442 package got it though.
I do not think you can go wrong with either rear bar. If the 1" is the same cost as a 7/8", then I would get the 1". Musclefactory Chevelle sells the 1" bars and boxed control arms and shims at a good price. You can go directly through them or they have an evil bay store.

Their control arms fit perfectly. They work with either size rear sway bar. I added them and a 7/8" sway bar earlier this year (thread "Lady's rear enhancements".)
If you get just the plates to weld in, consider changing the bushings while they are out if they are over 10 years old. Also they will need sanding and repaint! I found it most economical and fastest to just replace mine since I cannot weld or press bushings.

You may decide to upgrade to a larger front bar later, depending on how fast you wish to corner.......

Tractor Supply is a good source for the hardware - they sell by the pound, not the piece! I think grade 8 was standard.

 

My reference data says the front bar on a 442 is 15/16". The Vista Cruisers actually used a 1" front bar in the same years. The only factory rear bar for 1964-72 is 7/8".

As for sizing the bars, that's a whole 'nuther topic. The bottom line is that the A-body cars (and all Detroit-built cars in those years) are understeering pigs, even the 442. Increasing the BACK bar will make the car more of a neutral handling car. I would definitely go with a 1" rear bar, minimum. I'd also go with a 1" front bar at a minimum. My preferred setup is 1.25" or larger front bar and 1.5" back bar. Unfortunately, the latter is an expensive aftermarket part.

Of course, if you have no back bar now, even the stock 7/8" bar will be a noticeable improvement.

 

Keep the front bar larger than the rear or the back end will tend to come around on you in turns (oversteer).

 

I strongly disagree. The A-body is such an understeering car to start with that you'll be hard pressed to turn it into an oversteering 911 (well, unless you use the throttle to steer ). Even Herb Adams used a 1.375" front bar and a 1.5" back bar on his A-body setups.

Of course, this is just one aspect of handling setup. Tires, springs, shocks, and more will affect the dynamic response. Ultimately it's a matter of personal preference. Detroit cars have historically been set up to understeer because conventional wisdom says that an inexperienced driver finds this "safer". My response is that one should be an experienced driver...

Frankly, I'd rather hit a tree on the side of the road back-end first, not head-on.

 

Thanks everyone. Since my car is just a cruiser, I think I'll just go with the 1" bar setup. Like Joe said Anything is an improvement.