buddy of mine is puttin in a gm 847 w/ ported heads. are the ex612's big enough to handle the lift of that cam? if not, what would be decent springs to use? possibly 987's??

 

hey i you r looking to buy some springs i have a set for sell. they are the ex 618s they have alittle more sring pressure than the 612s and i know they will hold the 847, with ease.

the springs were installed on my heads, but never ran becuase im going a different route. ill sell them for 60.

i had to buy bigger springs so i need to sell them.



back to your question im not sure the 612s would work but i know people have had problems with them breaking, but the 987s would work.

let me know if interested

 

612s, no.

 

Definately N

 

nope.

 

Why not? They are rated at .600 lift and with 1.6s the 847 is under that. Maybe I should knock on wood, but I'm running them with success. Might I pick up some power with different springs?

 

Because they're too marginal to be safe with that much lift.

 

You probably will not pick up any power by switching springs, but you will be assured that your not going to break one and potentially damage your motor. They probably will not last long being a single coil spring good to .600 and you having .595 lift on the exhaust with your cam. I have the same springs in my car now and I have been having some valve float issues with the stock cam and 1.7 rockers.

 

I personally would only run a dual spring. It will help keep the valve under control better. Also the 847 with 1.6's is pushing .595 lift. The guy that helped build my motor said he likes to have .050 safety on valve springs if possible.

 

Thats also true. The closer you run a spring to its limit the shorter its life is.

 

618s are duals

 

I know this is pure speculation, but CM states that they are good to .600 lift. I would presume this to mean that they will work with a cam that has .600 lift, and NOT that they have coil bind at .600 lift. So, realistically, they SHOULD have the appropriate amount of extra height built in. Would that not be correct? Also, how many people have had these springs break? I'm curious because I think I've heard of one person with that issue. I would also presume them to be stronger than factory springs, and aren't factory springs run close to their max, considering you can't even run a .52x cam with them? I rarely hear of them breaking. I guess its all in what you've seen and what you choose. FWIW, not sure if any of you are familiar with Ed Curtis, but he doesn't recommend beehive springs due to breakage, and he has built NUMEROUS different combos, and I am hesitant to use them for that reason.

 

the spec sheet i have says they coil bind at .630 ans ive never heard of the 618s breaking. but im not saying they cant or even havent broke.

 

.630 minus .050 minimum clearance to coil bind = .580 max lift. The cam was .595 and that's to close.This is presuming the installed height was perfect for ALL valves,and the springs were meant to work with YOUR installed height.

 

Not to put a dent in this, But I have heard very respectable people around here tell me that those 612's were only good to .580...to support his statement

Also whats another 50 bucks or so for better springs or not, Find some good ones that will fit in the stock pocket and be done with it.....Unless he already has those springs.....