Rear End Sags While Accelerating
 

My '86 951's rear sags when I accelerate. It is most pronounced when I accelerate quickly from a stop. Becomes real annoying as I can't pull away smoothly. What are some possible cures? I am contemplating an adjustable suspension (coil overs). What are some good street orientated kits?

You are experiencing what is called "squat". All rear wheel drive cars experience it to some degree. There is no cure, but stiffer springs and shocks will help.

There are no street oriented rear coil-overs for the 924/944/968 series. The stock suspension uses torsion bars. Because of this there are no suitable mounting locations for rear coil-overs. Unfortunately there is a lot of labor involved in changing the rear torsion bar. If you are an accomplished back yard mechanic, the parts are not that expensive.

There are street oriented front coil-over kits. Paragon Products sells one that can be used in street or track conditions. They also sell replacement torsion bars and shocks/struts.

I just couldn't think of the word "squat" while I was writing, thanks. I know that rear drive cars squat but I don't recall my previous 944 or 951 squatting that much. I've seen the rear "helper" springs that were installed in the cup cars in the '80's.
I guess stiffer torsion bars might help.
What do you guys suggest in the form of shocks. Maybe I should replace mine, after all they are original and have 79k miles on them.

The generally accepted 924/944/968 shock upgrade for street use is the Koni Yellow. The yellow is the color of thier sports shocks. You should upgrade your struts at the same time.

Right now the struts are impossible to find, but this will change very soon. Talk to the people at Paragon Products if you want more info. A set of shocks is $228. I think the struts will be $300 for a set when they become available.

Lou- Sounds like you need new struts/shocks. Personally, I think the 951 is undersprung so I'd consider increasing spring rates too.
I had an '86 951 (street car) that I put a set of european Bilstein "sport" struts and shocks on (250 lb front springs and stock torsion)and it made a HUGE difference. (Windward Preformance imported them ... I don't know if they still offer them. They were not the "cup" stuff)
Springs will help with "squat" but dampers play a big role too. Remember, dampers control the rate (or speed) of body movement. Thus when you accelerate the front struts control the rate at which the front spring unloads (rebound) and the rear dampers control the rate at which the spring loads (compression). From what you've described it sounds like the original equipment is tired and a new set of dampers is in order. As Tabor stated, replace front and rear as a set. :)

25.5mm t-bars minimum. (helps quite a bit) - I don't understand why Porsche ever put anything smaller on the Cadill- err, 951...

My friend Adam runs 400# all around on the street. It is not unreasonably stiff, either.
I, myself, am moving to 350# up front, 30mm rear for my daily driver.

Thanks for the info, I will go with shocks first and take it from there.