Mar 2nd, 05, 01:36 PM
I sent this to David Pozzi and he refered me to you.
David. I just purchased a 67 SS-350 Convertible and I want to improve
>the suspension. The car will only be street driven. I plan to add
>front disc brakes and run 17" rims with good traction tires. After
>reading several articles I decided to inquire about a Hotchkis TVS kit.
>I was surprised when they told me that they do not make a kit for the
>convertible. They said that their rear springs do not fit. What do you
Well let's see, I'm a bit conservative in my approach so you may end up hearing a lot of different opinions once I post. Keep in mind that a ragtop is not as rigid as a coupe. Because of that I don't recomend any solid bushings as they just make the parts attached more ridged than the structure itself. I think a lot of guys mod their street cars for track conditions, it's cool to have a race car suspension but not real practical on the street. I think the best answer I can give you is to quote a few of the posts I have made in the past.
Originally posted by DjD:
I see it like this, decide what you want to do with the car, that is how do you plan to use it. Then assess the overall condition of the cars suspension and body bushings and go from there.
I believe this is the order you will see the biggest handling improvements.
Wheels and tires: Steel wheels and tall sidewalls don't cut in in the corners. The tall sidewalls may give you some ride quality but flex and give in the corners. The steel wheels are too ridged and low profile tires mounted on them will improve cornering but the ride will suffer. (This has nothing to do with bashing rally wheels with derby caps and trim rings, it's about seeing the biggest handling difference) A good alloy wheel with low profile wide tires will make the most noticable difference.
Shocks and springs: If you have good springs a quality set of shocks will allow them to work as they were designed. The best shocks can't make up for bad springs. Comparing to good condition factory type shocks and springs something along the lines of Hotchkis springs and Koni shocks will kick it up another notch in the handling department.
Sway bar: If you have a tiny 6cyl sway bar you will benefit from replacing it with something larger. If you already have a thick factory bar on the front the upgrade to a hollow 1 1/8" may not be that noticable.
Bushings: Stock rubber bushing will deflect more than urthane or solids. This will impact cornering but just how much on the street is the question I have. If what you have is in need of replacing and you have ride quality on the top of your list stay with rubber or urthane.
Sub frame connectors: Will add some regidity which will help cornering but may also detract from ride quality.
Then there are many other mods like tubeular A arms, rack and pinion and quick ratio steering boxes that will also help and may not really detract from ride quality. They all add up to the total package but there is a big difference driving around the track at laguna seca and driving on city streets. Finding the perfect combo for your liking is subjective. I had to do the changes I made one at a time do to finances and it's given me some insights into what did the most. If you just buy the parts and bolt them all up, stock today everything done tomorrow the total package will blow your mind but you won't be able to judge what really worked and what didn't. Hope all this helps... Originally posted by DjD:
I'm running the Hotchkis 2407C rear springs and 1907F front springs and Koni 80 1914 fronts and 80 1953 rear shocks. The front end is all stock rubber bushing except for urethane sway bar bushing and end links. The rear bushing are what came with the springs and I used prothane body bushing. With 17 alloy wheels and 45 series tires I have one of the nicest riding 1st gens I've ever ridden in. The shocks are on their lightest setting the suspension works very well. I'm sure on a closed track there is a lot of room for improvments but for the street I believe this combo is very balanced and you wouldn't be disapointed in ride quality or handling if you set things up this way. My car's a convertible so I do plan subframe connectors to finish things off.
If you design your suspension for your cars use you'll really enjoy it that much more... Originally posted by DjD:
When I got my '69 ragtop I thought it handled and drove nice with stock springs, Koni's (adjusted to firmest setting on all 4), a large solid sway bar, some poly (mostly rear and sway bar) and '60 series bfgs. The rest of the suspension is tight but stock. Then the urge to upgrade came, here's the order and my evaluation...
1> Hotkchkis 2" lowering springs, (reset the koni's to softest setting) Ride quality stayed the same, cornering improved some. (Rating: Noticable improvement)
Note to Shadow: At this point I took the ragtop up to 120+ for a short blast and all was smooth. It didn't feel like 60 but didn't leave me feeling like I couldn't change lanes. Your coupe should actually be better. I have heard that the rear spoiler on the first gen can cause handling problems. Too much push on the rear causing the front to feel light. I believe one of the Chevy mags published some tests a while back supporting this... If I recall they found optimal handling came with a front spoiler only. I don't have a rear spoiler on my car.
2> 17's and Z rated tires, (275/40's rear, 235/45's front. This forced the issue with subframe alignment to body.) WOW!! Cornering ability was greatly enhanced. Ride quality didn't suffer with less sidewall as the alloy wheels are not as stiff as the steel wheels. Too stiff a suspension could have an adverse effect on ride quality as well. (Rating: Big improvement)
3> Prothane subframe bushings, (Old were almost gone and the new ones restored body/frame geometry, which improved front tire clearence) Ride quality and cornering stayed about the same. (Rating: Necessary for optimal clearencing with big wheels and tires)
4> Rear Hotchkis 1 1/2" drop leafs, all new bushing and shackles, (new springs twice as thick as old) WOW!! Big improvement!! Ride quality is firmer but not rude and the entire car has a more solid feel. Cornering greatly enhanced. Cars stays noticably flatter in a hard corner. (Rating: Big improvement, almost as big a difference as wheels and tires.)
I feel the last improvement was the combined effects of a matched suspension front and rear and still give the tires the most credit for cornering improvements. I believe the suspension lets the tires do what they are designed for though and stress it's necessity for overall handling.
All evaluation based on seat of the pants feel. Timed track results may alter overall ratings but I believe would support my findings.
and here's a link to a bit more...