defiant1

I have #6 heads being rebuilt. Machinist calls me and say the installed height on the Comp Cams 942 valve springs is .143 over what it should be. The advertised installed seat height is 1.70 and he was coming up with 1.843.

So, I called Comp Cams tech line and they have no idea why the difference. Machinist asks if I have rotators for valve spring retainers. I have no idea. So I go home get my old parts and it turns out that (after some research) that 70 350 cylinder heads have deeper seats and due to that fact run rotators.

I bring the rotators to the machinist, he measures the installed seat height with the rotators and new valve springs and it measures to spec.

However, when sets the rotator on the spring to check fitment of the rotator as it relates to the inner diameter of the valve spring. There is some "play" between the rotator and the spring, whereas the comp cams retainer is a tight fit.

Sooooooo, with all that said can I safely use the factory rotators with the new valve springs?!? When everything is assembled will the tension hold everything in place? Would the spring have the ability to move around?

The valve springs were purchased based on the cam specs.

Valve spring specs:

Installed Height (in)
1.700 in.Seat Pressure at Installed Height (lbs)
115 lbs.Open Height (in)
1.200 in.Open Pressure (lbs)
284 lbs.

Cam specs: Advertised 268/284, 217/224 @.050 lift will be .494/.504,


Any insight would be appreciated.

d1

compedgemarine

generally when you remove the valve rotator you put a shim under the spring to make up the difference. I have never known a good machinest who didnt know that so now I wonder about his expertise.

defiant1

Isn't shimming .143 extreme?

defiant1

I found this excerpt on SupercarsUnlimited. So I might be okay...

SHALLOW OR DEEP SPRING SEATS?
Heads that were factory equipped with valve rotators will have .125" deeper spring seats than those that use solid retainers (see chart below). In performance and race applications, the (heavy) rotators should be replaced with solid retainers. Many aftermarket cam companies offer different solid retainers that will compensate for the .125" difference in installed height (or allow the use of taller springs). For street and street performance applications, originally equipped with rotators, we recommend using them. By turning the valve two degrees per cycle, the rotators virtually eliminate any carbon buildup on the valve seats and valve faces. Thereby increasing the life of the valves and seats as well as maintaining compression. Oldsmobile engineers found in a wide open engine test for 1300 miles at the equivalent of 130 mph, the performance loss was 50 percent without the rotators and only 9 percent with the rotators! This more than makes up for the extra weight of the rotators over lighter retainers in a real world street application.

Warhead

I don't normally run rotators, they were always a little bit sloppier.
115#'s will hold them, I'd rather run with normal retainers, I don't like sloppy.

You have a couple of options, in order of my preference.
#1 You can exchange the springs for some 972's, or equivalent.
#2 Get some "deep keepers", offset .060 tighter (puts the retainer .060 closer to the seat), and run .080" of shim. Not sure if Comp sells these, I know most shops know about them, they might be available through a PEP dealer.
#3 Shim .140". I've seen worse, at least it will be assembled to the correct height. That is what counts.
#4 Run the rotators. I've never seen that data before, I'm open minded, slightly doubtful on it though.

Remember, shims are your friends.

Jim

cutlassefi

Or instead of shims you could also get some spring cups or seats. They are normally about .060 and are a bit sturdier than regular shims. That along with some offset retainers or keepers should set you straight.

Or also like Jim said, you can exchange the springs for the right ones. You have a couple of options.

defiant1

I have read that shims have a tendency to get torn up. What causes that, spring contact?

Ok - " the right springs" well, I was trying to get valve springs that were as close to the factory installed seat height of 1.670. So I purchased ones that were 1.70. Now I am suppose to get 1.80 instead??

I don't follow...

Warhead

I understand your dilemma, and I wasn't trying to be a smarty pants.
If you can exchange for 1.800 springs, by all means do that. The keepers are the next least expensive way to go, other than using the stock dampers.

Sometimes, sometimes there can be an issue with the inner damper chewing on the shim on high mileage applications, if the shim is not hardened. Most shims are not hardened, they are more expensive. I like to use a hardened shim right under the spring itself, if it has an inner damper.

Jim

cutlassefi

I would, or use a spring seats, much more durable than shims.

Warhead

Yeah, Comp sells a hardened spring seat cup locators for roller cam applications, .060" thick, to keep 600#+ springs from chewing into the head. Inexpensive, and would handle 2 problems at once. Look for part number 4770-16, you will have to have the guides cut to less than .575".

Jim

defiant1

Jim- I did not take it that way. Damn typed words apparently can't hide my apparent frustration.

I know you guys are trying to help and I appreciate the advice. I will see if I can't exchange my springs for the 1.80 and go from there. Hell, I thought this was going to be the easy part... Oh well, I did not get a warm fuzzy when I saw the rotator being loose in the valve spring. The machinist thought it should work since I was not going to being operating at high RPM. But I just watched a video of a spring in action and there is a lot of vertical/horizontal movement, so if I can minimize that I will.

d1

defiant1

I will check that out as well.