I searched around a lot, but couldn't really find the answer to my question although i thought i had seen it on here or some other site awhile back. I wanted to make sure that if you were to run these springs (comp 987's with 1.6rr's) on stock heads that there would be no machine work required, or does it depend on other components also? Thanks in advance for the help, and sorry if this has been asked before.

 

I believe they will work, but someone who has them will answer. When determining whether you need to machine your heads for a particular spring you need only look at the Outside Diameter of the spring compared to the diameter of your seats. I forget what stock seats are, but again. someone will chime in. If not, I will look into it later.

 

Diameter on a 987 is 1.430" and that does need to be machined on stock seats. Comp Beehives and some of the CMS springs don't need to be cut.

Bret

 

I believe the stock seat is 1.25, but there are lots of springs that will fit and accommodate 1.6 RRs. The one thing you might consider is what size cam you might run and get the springs to match the cam card requirements.

You can get springs that will fit and handle a mild cam too.

No point in getting marginal springs and have to change them later to work with the cam. JMHO

 

Also, I am really wondering what size the stock seats are on the Lt1 heads: I am relatively certain that my springs, Crane 99893, has an OD of 1.460 and I don't believe that my heads were machined.

I could be wrong. Perhaps it's the vortec heads that are 1.25 and maybe ours are larger.

Something to ponder.

 

I just got done putting a set on and I heard They didn't need to machined, that turned out to be very untrue, Comp also said that you could use the stock shims, also bad info. You will need to macnine the heads to get the correct installed height and you will also need a set of spring cups to locate the springs, otherwise they will just rub on the valve stem seals. If I had to do it over I would have went with 918's. I tried to just put them on like everyone said they did and checked it, coil bind at .400 .

 

Thanks for the info so far. Ok, well i am going to be running a cc306, a new set of oem lifters, hardened pushrods, 1.6rr's preferably SA, and i was just having trouble trying to decipher all the numbers and stuff on the valvesprings. Im new to this, and ive been researching quite a bit, and I kept coming back to the 987's, but the thing is i really don't want to have to machine the heads. Is there a spring for sure that i can run safely w/o machine work?
Comp cams tech page recommends the 986's. Both 987 and 986 have an OD of 1.430, any opinions?

 

The comp 987 spring will fit stock seats. Where you run into trouble is with the locator supplied because of the 1.5" OD. What I did was just notch the locator so it would fit the stock seats. Theres only a couple of places were it will hit the casting and not sit level.. not a big deal cutting the locators if you have a grind wheel.

 

It's a big deal cutting them ON the motor..... spring pockets are only easily cut with the heads off and the valves out.

Bret

 

I believe we have come to the conclusion that they will fit stock head. JMHO

 

IF you turn the spring seats down to fit the heads it will be a drop in installation.

Bret

 

Thats what turbo_z meant. I was there when he did the install. You just have to cut a small notch out of the spring seat so it will clear the notch on the head.

 

Cool, thanks for the info.