How many have used the GM copper shim for LSx springs?

[SappySE107]

Im not sure where this originated exactly, but I recieved a set of these copper shims for use on the older gen 3 heads that have the smaller outside diameter valve guides for a head porting job I did. Thank god they didnt fit the newer heads! It seems someone has been saying that the shims (part number 1256511 are good to be used as a valve spring seat when using the LS1/LS6 springs on our cylinder heads. This is a bad idea.

The copper is not going to protect the aluminum heads like a steel seat will. They are shims, meant to increase the springs pressure by decreasing the installed height. Not only are they a bad idea due to their material, but they are also a tad on the small side and the spring hangs over the edge.

Phil is looking for a good set of seats to use, since GM doesn't sell LS1 spring seats without the heads (wtf). Aftermarket is plentiful but it would be nice to find something that isn't quite as thick as the isky VSL-950 seats. On a stock cam, the LS6 springs come real close to coil bind using these seats and it scares me to think that some people are running around .500 lift with these springs.

[gpse3400]

I use them since my heads are older than "00. But make no mistake Ben they look the color of copper but they sure as shit are not made out of copper. As far as them working...they do. It's one part I didn't have to overhaul. The LS1 conversion is Chris' baby. Included some pics, it looks like coil bind its not touching at all, just a bad camera. Also included a pic of how the 440-T4's TV cable would get attached.

[tejohnson]

Maybe a copper coating, but definitely not copper. In the following pic you can see where I had to open up the ID a tad to fit flush against the seat on a set of 99 heads. You can see that underneath the coating, they are steel:

[Rhedalert]

I can vouch for that too, I removed the LSx shims when disassembling my heads, with a magnetic pickup wand

BTW I just got the Isky Cams VSL 950's, why do you think they're too thick?

[SappySE107]

How many miles were on them? They do take a while to grind through so that takes care of the material:P Not something I wanna grind through to make them work.

The isky valve spring locators are excellent quality but they are .055" thick. $60 plus shipping is the cheapest I have found so far.

[geoffinbc]

If they were copper they would be mashed to shit in a matter of minutes. Just like the aluminum heads would be if you didn't have a steel seat.

[gpse3400]

I had to grind into the them for Tat's engine and they are just fine. Lord knows his engine has more miles on it than mine. Using a grinding wheel, you can cut through them for an exact fit.

[Syn]

i'm using them on my 00 heads with no probs with overhang, had to open the center up just a tad but no prob