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Cylinder Head Assembelly

732 Views 10 Replies 2 Participants Last post by  Grannynational
Heres what I got when I mic'ed the vavle spring clearence for the installation hight.

Head 1
1 2 3 4 5 6
1.772 1.767 1.767 1.770 1.758 1.722

Head 2
1 2 3 4 5 6
1.723 1.727 1.737 1.731 1.743 1.722

I have a set of Kirbans wonderfull vavle springs that were allready in the car and a set of what I "think" are comp cam 979's. The Kirban springs havent wrecked my cam so I think they are good to go, and I would like to run them since the GN see's the track more often than it should and I want all the power I can get.

Should I just put the kirban springs and shim them all as close to 1.727 as possible or put the 979's in there with a little extra shim, mabye install them at 1.707. powersix powersix

any ideas?

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Do you know why the Kirban would give you more?

Just dont want to float the valves, the other springs were tested 70lbs at 1.727 I figure there is going to be 25# of boost trying to open the valve.


<small>[ May 31, 2003, 04:28 PM: Message edited by: Grannynational ]</small>
I guess I'll run the comp cam sprigs, the only thing is I'm planning on leaving them about .005 to .015 loose on the install hight to save the cam.

I'm guess, I should also stop listening to my ford and chevy friends

Have not seen it happen yet. Not until the springs are weaker than that.

Factory specs are 78 lbs +/-4 at 1.727" and 185 lbs +/-10 at 1.340

If it were me, I would use the 979s and shim them to about 85 lbs.

With the comp 221 that I used to use, I ran the 980s at whatever height they were speced to and turned over 6000 rpm at high boost with nary a problem. The cam profile was obviously more gentle than stock, but, I never blew a valve open.

But, as you don't live next to me and I ain't gonna be helping you do the work....do what you like! :D

just for ****s and giggles I mic'ed my virgin stock heads and the installed hight on those was anywhere from 1.707 to 1.715.

any Idea how much shim increases pressure, or am I going overboard and just get it close to 1.727 and call it a day with the 979's

Steve, I listen to you for the same reason everybody else does, you know what the hell your doing :D :D

I shimed the 979's an extra .010 and put them together, there going on the car tonight, now I just have to port the intake a little more yup powersix
You have to look up the spring rates and compute how many pounds per inch...Comp used to list them. You will be okay. :)

I don't see the 979s in the catalog. The 980s are slightly stiffer and were rated at 91 lbs at 1.700" and 229 at 1.250. I calculate that to be 307 lbs per inch and the catalog says 308. That would be about 3 lbs per .01"

If your average height was 1.71 and you used a .01 shim, then you would have been at 1.700 and a theoretical 91# if you had been using the 980s. Seems like the 979s were like 6 or 7# less than the 980s so you would be in good shape.

Lots of people just put the stock cups back on with the 979s. I am not surprised the is a little difference between factory spec and what you measured...close enuf.

<small>[ May 31, 2003, 07:14 PM: Message edited by: Steve Wood ]</small>

Zap posted this a bit back..

I got this a while ago from the GNTType mailing list archives (I think Ken Mosher posted it):

OD(in.) Closed# Open# Rate(#/in.) Part number
> 1.20 80 200 267 VS677
> 1.23 85 230 295 VS1615 - Sealed Power numbers
> 1.264 105 277 350 VS739R
> 1.24 80 200 267 CC 979 - Comp Cams numbers
> 1.23 85 230 325 CC 980
> 1.25 110 285 ? CC 981


So basically the sealed power vs677(80lbs) or the vs1615 (85lbs) are close to the Comp Cams 979's\980's Steve mentioned. They are available at Advance Auto, maybe Autozone too.

That computes to 260 spring rate or 2.6 per .01

Sounds like you will be right around 80# if you did not use the stock cup and used a single .01 shim.

I am bored, too hot to go out to the shop

<small>[ May 31, 2003, 07:14 PM: Message edited by: Steve Wood ]</small>

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Thanks Steve, I think I tossed the stock cups in the garbage a while ago so I just used the valve spring shims to get what I needed. Appreciate the help, I owe ya a beer.

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