[ronron]

my front springs are flat. my tired old 86 cj7 only has about 1.5 '' travel between front axle and rubber bump stop , 3.75'' for rear. any idea how much higher it would be with new stock springs? this march im swapping in a 400 sbc with a nv3550. i want to keep near stock height but im not sure stock springs will handle xtra weight. any idea about 2.5'' lift springs as to how much travel between axle and bumpstop? im running 31'' bfg all terrains. all the salespeople cant give me any idea how high 2.5'' lift kits are so i figured if i could get measurement off the stock bumpstops it woluld help. will a 2.5'' yj lift have the same height as a 2.5'' cj lift kit?

[foggybottombob]

If your springs flex much at all, then the usual limiting factor you would use to set the height of a bump stop would be the limit of the shock compression. If you have more than 1.5" of shock compression left then you can make that bump stop shorter. The bump stop should just hit before the shock bottoms out so you don't tear up your shocks.

In the back, the shocks are set at an angle. I guess it is about 30 degrees from vertical. So since the axle travel is almost vertical, when the axle travels straight up to the bump stop, the shock will not compress as far as the axle travels. The shock will only compress at a rate of the cosine of the angle from vertical. For 30 degrees that is about 0.87.

So if you have 2" between the axle and the bump stop in the back. The shock will compress about 0.87 times that amount (0.87 x 2 = 1.74) or about 1 and 3/4".

In the front the shocks are pretty much vertical so the axle travel and shock travel under compression is about 1 to 1 or the same if you want to think of it that way.

So if you change the springs, make sure the bump stop hits before your shock hits bottom.

[ronron]

im not worried about shocks bottoming out because front springs are flat and hit bumpstops all the time. im just trying to figure out how much higher new stock springs will raise it from where it is now. also if added weight of engine swap will cause new stock springs to flatten out.