What is the highest open and installed spring pressure you can run and still run a GM lifter?

 

The answer is "it depends".

It depends upon the dynamic loads the lifter feels when running. Agressive lobes, heavy valvetrain parts and high rpm are all going to cause dynamic axial and side loads added to the spring loads. The lifter doesn't care what causes the loads.

Questions for you:

Which GM lifter?

Why do you ask?

 

The same ones that come in the car stock, but new of couse. I want to put springs with 150lbs on the seat with a relatively mild cam. I already have the springs thats why I wanted to use them.

 

cms 612 springs were @ 320 open if I remember correctly - did fine
crane spring for the 847 was @ 360 shimmed - roller exploded - cam, block are trashed

It all varies.

 

Why don't you just go with the gmpp "caddy" lifters, they are only around $200.

 

Can you find them now?

I am just going back with my old springs because I am running a 218 baby cam

 

As far as I know they are back in stock, I've been running mine since december.

 

Ask the cam designer (or cam manufacturer if it's a shelf cam) about the amount of spring seat and open load you need for your cam/rpm/valvetrain.
If the springs are inadequate, you may have valvetrain issues at higher rpm and perhaps lose some of the power benefits of the cam. Worst case might be to hurt parts.

New roller lifters aren't always needed. Again, discuss this with your cam person. Depending on what the cam is, folks here might be able to advise, but they would need specifics.