Jaxem

iTrader: (3)

Hey everyone, getting ready to do a top end swap, i bought a used cc503 off a member here and don't have the cam card, i can't seem to find the valve spring installed height spec on the CC site. anyone know/have this info?

Thanks!

93M6Formula

My CC503 recomends 1.800" installed height. That's with using Comp 918 Springs.

ACE1252

Back when I was doing my CC503, I got PAC1518 springs on a group purchase.

As best I can recall, I think the install height recommended was 1.75 with the retainers and locks I was using.

When I measured, most of them were 1.78....I left them at 1.78.

We will need someone with more experience than me to chime in on this as I know just enough to be dangerous on this topic....

Edit: Looks like 93M6 beat me to it. =)

lt1-xjs

The spring you use dictates the installed height. The spring has to handle the max lift of the cam. There are several options for that cam.

Jaxem

iTrader: (3)

I'll be using Alex's parts springs, the listed 130 lb seat pressure is at like 1.78... Sounds like in that neighborhood should be fine

BALLSS

^^^^^ This.

cam card will show what spring it recommends. Likely the 918. That spring spec for its published seat & open specks is 1.800" installed height. Setting up a 1.800" speck spring a little shorter will increase the springs open & seat pressure. setting them up at 1.780 for example, IMHO, would not be a problem. More important to set all the springs the same height

Jaxem

iTrader: (3)

Fair enough, now if my heads have never had any work at all done on them, would i need to take a micrometer to every spring? or should i be alright to check one or two and treat them all the same?

BALLSS

when you pull the stock springs off you may find shims under some, all or none of the springs. IMHO I would use a valve spring height measure tool and install shims under the spring locator as needed

the spring height tool does not measure the spring by itself, it measures the distance from the top of the locator to bottom of retainer. You want that measurement to = whatever the springs speck installed height is.

get a spring with a installed height to = your stock springs (1.750-1.780 in height

many aftermarket springs are speck for 1.800" height which would require the spring pockets to be machined down to get that height. If you install a 1.800 spring a little shorter than its closed and open seat pressure is higher by "X".

Crane 10308-1 kit is a stock height spring and Alex Springs also offers a drop in kit for the LT1 AL head, do a search for part #

you will need new valve stem seals and it is a good idea to buy a pack of shims. They come in various thickness and you use them under the spring locator to raise it so your installed height is 1.750 or 1.780 whatever the installed height speck of the spring you get

use a spring height measure tool to confirm installed height. Maybe all your springs will wind up not needing shims, some may, all may.

Jaxem

iTrader: (3)

Thanks for the comment, I know the micrometer doesn't measure the actual spring, though it did sound like I thought that now that I re-read it. I mentioned in a previous post in this thread that I bought the Alex parts kit and we'll be installing that. The spec on those is a 1.780" installed height, but when I sent Alex an email about it he said it depended on the cam more than the spring. I'm going to just try to get as close to that 1.780 as I can though. 130 lbs seat pressure is plenty, and the springs have lift to spare with the 503

I'm just curious how with brand new springs and untouched heads, how some might need shims while others don't?

BALLSS

Because the spring pockets may be machined "slightly" different on the GM AL heads. Not saying you will have different size shims under spring locator but you may....which is why you want to measure each one as you swap springs. You may not even have any shims...just the hardened steel spring cup or locator. You need these especially with AL heads as the spring material is much harder than aluminum head

The Alex springs set at 1.780 will give you the published spring rate for that spring installed at that height which I would think is way good for the 503 cam

Jaxem

iTrader: (3)

Great, thanks for the input, I feel a little better about doing this swap now.