Originally Posted by V8Square
So then, maybe something like a 225/75 or 235/75 may do the trick. I would have about 5" clearance from bottom of my oil pan to ground. What do you think about that? Enough? Guess I could always add some taller coil overs also
In my experience, the absolute minimum is 4" for a street-driven car. I used to keep a 4" by 4" piece of wood, about 16" long, laying over in the corner of the garage. If I had a component that looked like it might be questionable, I'd get under the car to sweep the block of wood under it to see if it cleared and by how much. If the car is close to being done, this works fine, but if the car is just getting started and you have engine, transmission, cooling, exhaust and so forth to go yet, then you might want to give the item in question a little fudge room. You can figure it pretty closely if you know the front and rear spring rates. 350 lbs per inch is common for front springs, so if you have, for instance, 900 lbs of motor, trans, cooling and other items to go yet, then you can divide 900 by 350 and find that those items will lower the front of the car about another 2.57", or about 2 9/16". Divided by two springs, that's about 1 1/4". It's just math, but if you've got 5 1/4 inches of clearance on the pan, you're golden if the car has most of the heavy stuff on it already.
Let's say that you weigh 200 and your passenger weighs 150. That's 350 lbs supported by two 350 lb rate springs and two 200 lb rate springs. Total spring rate is 1100 lbs, so 1100 divided into 350 drops the body 0.318 inches, or a little over 5/16" when you and your passenger get aboard.
Here are some photos for the fellows who are not familiar with this replica car......