ZeeOSix

Yes, IMO PAC 1518s are one of the best replacement springs. I went with them after doing a lot of research on springs.

Also, if you measure the wire diameter, it's actually slightly oval shaped I believe. You might want to measure the wire diameter in both directions and report to verify.

Here's a couple of other specs on the 1518s to help out.

Weight = 75 grams
Coil bind = 1.140" (from the 1.800" height)

tungstenfoot

Thanks ZeeO! These checked 72 grams. I guess they could be PAC1218 too? The wire does check ovalized:
From ID to OD direction, dia of wire checks .202".
From bottom to top direction, dia. of wire checks .166"

For future reference, the Blue Springs GM PN 12625033 check ovalized too:
From ID to OD direction, dia of wire checks .212".
From bottom to top direction, dia. of wire checks .170"
(These measurements obviously include a small amount of blue paint)

So, now what..stick with these? Use new GM Blues? I guess it depends on IF all the install heights check to spec...so I checked a few with calipers and its difficult to get accurate reading with them. I was getting 1.800" +/-.009, which was from the head machined surface to the underside of the top retainer. are these the correct surfaces to measure?

Asked a different way: If I get a spring height micrometer do I remove the valve seal/seat or do I use the measurement with the valve seal installed?

ZeeOSix

The 1518s will have a very smooth surface and be kind of gold colored ... this is from the microbeed blasting and nitrited surface treatment. The 1218s are have a rougher surface and are more grey metal colored I believe.

You have to measure with the valve seal in place because the steel base of the valve guide seal is the seat the spring sits on and acts like a shim. The installed height of the spring is when it's sitting installed with the valve closed, and part of that system is the valve guide seal installed. You will probably find that distance to be around 1.780"-ish ... which is perfectly fine. I have never heard of anyone having to use additional shims on top of the valve guide base.

tungstenfoot

lol mine had extra .016" shims installed... go figure! leave it up to me to be the first.
Well, measuring with the seal in place & of course valve fully closed, gotcha-makes sense. I loosened the rockers from the pedestal and tried to measure with calipers but I can't catch the top of the valve seal flange...I definitely need a micro-height tool special for this. I did check the flange thickness on the valve seals, they check .042" - .047" thick.

Since I have to remove the .016" shims and replace my rocker pedestal, I might as well buy a gauge and check them all while I have it apart. I think I'm going to sell these springs and my new OEM blue springs and just get new PAC's. I started this project to reset the hours on the valvetrain, might as well do it all new...its just working out to be WAY more expensive and time consuming than I thought...but, its piece of mind and heck, I learned alot in the process too! bonus

ZeeOSix

That spring looks more like a PAC 1218 because the surface looks too rough and it has a more gray color.

Here is a photo from PACs website of the 1518. It's more gold colored and very smooth surface.


Note that per the PAC Racing catalog, the 1218 and 1518 have all the same dimensions and specs. The difference is the 1518 is a 1218 with added micro-blasted surface and nitride treatment which gives them more lift capability (0.625" for 1518 vs 0.600" for 1218) and reliability.

Here is a photo from PACs website of the 1218. See the difference.

tungstenfoot

^^ I agree. It seems most likely mine are PAC1218's. Thanks for helping me through this!

This Spring Height Gauge ? wierd. The part #'s are same but pics show different top features...
http://www.proformtools.com/product-...ategory_id/170

http://www.summitracing.com/parts/pro-67390/overview/

ZeeOSix

Glad to help solve the mystery.

Same P/N listed on each website. The description on Summit Racing says the finish is black, so photo is probably old. I'd guess the black one is the current build.

BlackZ2003

My 03 vin 24549 experienced valve spring failure at 57k miles

VROOM66

2003 Z06 31,4xx miles. Build date is 9/2002. No failures, but I had new springs and seals installed. Went with PAC 1218's. Old springs were yellow. Thanks to all on this Forum for the heads-up and for the great analysis.

RED02Z

Gracias for this thread. Whoever is responsible def deserves props.

LuckySon

Just had mine replaced for good measure. I did NOT experience a failure.

2003 Z06 with 17,134 miles on the odometer. Late year build, VIN XX119079.

Replaced with COMP Cams springs at Cooper Corvettes in Triangle, VA.

rbartick

2002 Z06 16,xxx miles, build date of 2/2002, no spring failures. I just installed new GM springs and seals. My original springs are yellow and the replacements are blue.

lilesv

Replaced my '03 Z06 (built 11/02) springs with COMP cams [105 lbs@1.800"; 293 lbs@1.200"; 313 lbs/in spring rate; coil bind 1.140]. Old springs look just like the new ones (sort of bronze-y), only significantly shorter...

Corvette_D

2003 C5 Z06 with a little over 35k miles on it. Build date is 10/02. Changed the valve springs on 6/27/2014. I did NOT have a valve spring failure. Old ones are yellow, and I still have them. They look like they are still in good shape. I couldn't find any cracks or anything.

The new ones are blue. The part number the dealership gave me for the new springs is 12625033.

Fast Lane

April 3, 2002 build for my Z06. Started the spring replacement today. Original yellow one's are good at 49,000. Putting new blue replacements in GM# 12499224 Changed the valve seals, plugs, and wires.

jml_911

And another C5 Z06 with a broken valve spring

Jan 2002 - ***** 113532 /64,000 miles / yellow

Trash

This is kind of a tangent, but I have a JAN 2002 build with a VIN#xxx119306. Kind of curious about GMs numbers.

Trash

I have a 2002 build which I installed new springs too. I did not have a failure. The odd thing is I ordered the exact same springs as you and others did BUT my new springs are yellow too. I am possibly the only person to have this happen.

I will be the black sheep experiment and continue to run the new yellow springs. Originals were replaced at 22xxx miles. New yellow have 45,xxx on them (67xxx total on motor). When and if she blows I'll let you know, but for now its full speed ahead.

skyavonee

That date and VIN don't match up, according to my records. Please verify whether or not one of them was mis-typed.

CGGS

Where is the cheapest place to buy the GM springs from? What is the part# I see conflicting part#'s in some of the posts

Do they include the seals, or do you have to purchase that separately?