Wondering at speed

[Rolls 912]

Hi
I'm in the home straight of fine tuning my 68 conversion car (3.2 in rear- weight).

Just installed sticky 205's. Much better however the car still wanders at speed and can be a handful.
Everything is new/been replaced etc. The car has also been professionally aligned. it has turbo torsion bars at the rear. I believe it needs to come down an inch font and rear.

Appreciate it will never handle as well as a stock car with the weight situation, however I do believe it should be better than what it currently offers....

My question is, what would be causing this 'lightness' at speed? Could it be the excessive weight?What should be the order of what to tackle first.

[hoffman912]

was it aligned before you did the engine swap? If so thats probably going to screw up your corner balance..

either way sounds like something isnt in alignment

[RSTarga]

Is it lightness or wandering? First make sure your alignment, ride height, and corner weights are set. What tire pressures are you running? Are your shocks matched to your TB's? Is it aerodynamic? do you have any spoilers or spitters?

[pcpaternie]

Check the wheel toe front and rear then camber

[Richard]

Because it's a SWB car with a heavy 3.2L in the back you probably need more weight in the front. A simple test will help to determine if that is the problem. First, run the car on the fwy with very little gas in the tank and then run it again with a full tank. If it settles down somewhat with the full tank of gas I'd figure this your main problem. To solve it, I'd first, lower the car the 1" front and rear you say it needs. Second, add some weight to the front end. I hate to suggest it, but Porsche put those 25 lb. weights in the front bumpers (one on each side) of the SWB cars because of exactly what you are experiencing. If you have a SWB steel front bumper they will fit right in. If you have a '72-73 S style front bumper (which should help with the wandering) you'll have to figure out another way to add some weight to the front (think of what they did with dual batteries in the '69-73 LWB cars and you'll come up with something.) Good luck.

[Rolls 912]

Wondering - wandering - thats what happens when you post late at night

Okay thanks for the replies.
I bought the car as a roller so I canno comment on how it would have handled previously
The car is standard, no splitters etc.
It has the lead bumpers and Full tank makes very little difference
It has been aligned to all the correct settings. I'll see if I can find the measurement data. It has about 1.5 deg of negative camber on the front -the towers are as far accross as i could get them. Do you think I need to get this to 0 degrees by way of minor modification to the top holes?
New shocks, joints, bushes etc
Body appears to be very straight so I don't believe it's a tracking issue
Tyre pressure is 26 and 28psi
I haven't corner balanced it yet as I don't have access to scales. This is my next project. It will be tricky considering the weight issue that I have

Can anyone else think of what else I need to consider? It really is a handful.

Cheers

[hoffman912]

were there any signs of an accident? could it be that the a arms or controll arms might have issues, or that the pan was not properly installed?

I would think the alignment shop would catch this kind of issue and note that it would be nearly impossible to get a perfect alignment with damaged pieces?

you did take it to a shop right? or did you do an at home alignment? if you took it to a shop and just got it back, i would take it back and tell them they didnt do it right...

[Rolls 912]

Hi Harry
Yes I took it to a local Porsche man. All correct however he did say I would need to reduce some of the front camber. I don't want to pay money to get it lowered and realigned until I am certain everything else is correct. The body is very straight. I'll post a copy of the alignment report today for review.

[RSTarga]

I'd try 29/34 tire pressure although it sounds like something more serious. What is the condition of your suspension bushings? Does it understeer or oversteer on corner entry? Is it different at low or high speed corners? Is it stable under braking? Does your steering have any wear? Tie rods in good condition? Can you better describe the wandering?
Something sounds wrong with your front camber, normally it's harder to get more camber than less. Do you have any play in your wheel bearings?
I know this sounds like a lot of different things but you have to start at the basics and then move to the adjustments.

[obrut]

I'd get the whole package assessed and the alignment done again by someone with experience with SWB cars, preferably track experience. To me, it sounds like at least the front toe is off.

I run zero front toe on my race car - great for initial turn in but not so great for straight line stability. Some front toe-in is a good thing on a road car.

1.5 neg camber on the front is fine - so long as you can get a little more on the rear. If you can't get 1.5 on the back then I would aim for 1 or .5 less on the front than the max you can get at the back.

You mention turbo rear torsion bars - what about the front? They should be upgraded in front/rear pairs.

18.8/25mm
21/28mm
22/29mm
23/31mm
24/33mm

Lastly, the shocks also have to match the springs. Have they been re-valved to suit? A dead shock will lead to very weird handling.