? 0n shims on comp 980 springs

[onefastgn]

Will i need to use .40 shims in place of the old oil shields when changing over to comp 980 valve springs to get them back to stock height. I see that some have and some have not used the oil shields on 980 springs. Which is the correct way to do this. i just don't want to have to redo them again.
If so then why.....
If not then why.....

Thanks

 

[thessman]

No factory shields on the 980 springs. They have an internal dampner where the factory spring does not. you will have to use a .030 and a .015 shim.
I think they are a 203 part number. usually .015 to get your 1.725 installed height. what retainers are you using? .040 seems like alot unless your valves are sunk. Steve

 

[onefastgn]

No factory shields on the 980 springs. They have an internal dampner where the factory spring does not. you will have to use a .030 and a .015 shim.
I think they are a 203 part number. usually .015 to get your 1.725 installed height. what retainers are you using? .040 seems like alot unless your valves are sunk. Steve

I am using the 742's retainers. So if i understand you correctly i will need to shim them to .015. I just used a gage to check the thickness of the cups that were removed and they were .040, so i thought i should use the same thickness shim to replace the cups that were removed. have you done the same?
Thanks

 

[thessman]

PMed you

 

[bison]

Use an installed height checker. There is no amount of guessing that will make it correct.

 

[gnxtc2]

Use an installed height checker. There is no amount of guessing that will make it correct.

+2

Also replace your keepers while you're at it.

Billy T.
gnxtc2@aol.com

 

[onefastgn]

All done and i wanted to say thanks to Steve ( Thessman ) for all the help over the phone. It runs great. I tested a few of the old springs and they were anywhere from 10lbs to 15lbs out of factory spec. I did add a 0.015 shim to all springs to get them close to the 1.700 installed height on the 980 comp springs. They are only 0.010 out. But like Steve said that's only 3 lbs for every 0.010. Pulls alot harder on top end. I also added my old set of heavy duty rocker arms and shaft to help hold things together under higher RPM. All i can say is the back R/H too are a bitch to change. But i modified the spring tool by taking off the top handle and welding on a 13/16th nut to the top and was able to reach both back springs with no problem. Thanks again Steve for the help, and everyone elses comments.