I have a set of 986 springs that i just stuck on my LT-4 heads, comp cams says there needs to be 1.800 standing height and the stock LT-1 is only 1.750. Im not sure if the LT-4 is the same or not. un-fortunately I dont have a height mike and my dial caliper is less than convincing. Who has run this setup before? Do I need seats machined?? Thanks.

 

I have 987 springs on my LT4 heads, the outer springs are identical with the 986, the only difference is a slightly stiffer inner spring.
With LT4 heads and because of the raised intake runners, the spring seats are relativly lower than LT1, so you have to machine the seats to make the spring seat fit, u just have to enlarge the diametre not the depth.

 

the seat width looked fine, i put the springs on and they seem to fit fine???? I'll look at it again...... do you know what your installed height was?

 

The problem is at the seats over the intake runners, the spring seats I used were 1.55" this didn't fit and I endded up machining about 1/8" from that area (used a Crane cutter and arbour, done the 2 heads in about 30min).
The installed hight is stock 1.75"

 

I took em to a machine shop and said I need 1.800 standing height and 1.430 outside dia and they said it would be 3$ a spring and they would even install em for me. Cant argue with that.