Setting up valves. Confused. SBC

My work schedule beat the berk out of me this year so I basically requested and got all of December off.  That gives me some garage time and so I’ve turned my attention back to my junkyard 350 that I started on and made good progress with last Christmas holiday.  Got the whole bottom end done.  New cam that’s basically 1 step hotter than an L-48...so mild.  Ported the heads.  882 castings so I wasn’t afraid of screwing them up.  I didn’t.   Now comes to putting the heads back together.  I got new valves and lifters (hydraulic) but I had planned to reuse the springs.  I was reading on here about the fellow with the SBC swapped 260Z who didn’t have the rocker arm tightened down enough and consequently his valves weren’t sealing.  The directions you folks supplied seemed easy enough to follow and I thought I understood it.  Then I started reading on some hot rod site (maybe HAMB) where everybody was saying that the installed height of the valve needed to be set via shimming to 1.7” + or - xxx.  What is that and how do you even measure the installed height of the spring?  Also, as it turns out, my valves aren’t even all the same height exactly.  

See fifth one from the left is shorter than the others.  There are a few that are shorter.  Is that going to be an issue?  I have no idea of the history of this engine. I can easily spring for new springs but if I don’t need to I won’t.  This will not be a race engine...unless some clown insists on racing in which case I’ll run it until it blows.   No idea what it’s going in.  I’d like to get a mid ‘80’s full-size van back dated to early ‘70’s.  

I think you would be a lot better off with new springs.

It would suck to have an unknown origin spring break and drop a valve destroying a new engine.

And yes, you will most likely have to shim to the proper height.

Spring installed height is determined by installed spring pressure. You need a spring tester to do it correctly. But if you're putting together a street motor with a mild cam you needn't go through all that.

Some heads use different height springs to make up for the exhaust rotator retainer thingie. Other heads have the seat pockets cut deeper to make up for it.

I did 882 heads on the 350 in my Firefly, and I used all new Lunati springs, but I'm pretty sure I had to do away with the exhaust rotators because they 882's used different height springs.  I can't remember exactly, it -was- like 6 months ago.

It’s not shorter - or at least not as short as it looks.  Springs are twisted. And on that one, you can see the end of the spring/twist on the left is as high as the spring next to it. 

Oh it’s shorter.  I checked them all with a digital caliper.  While they’re all over the map, which isn’t unexpected, two are out layers.  

A 401 CJ said:

My work schedule beat the berk out of me this year so I basically requested and got all of December off.  That gives me some garage time and so I’ve turned my attention back to my junkyard 350 that I started on and made good progress with last Christmas holiday.  Got the whole bottom end done.  New cam that’s basically 1 step hotter than an L-48...so mild.  Ported the heads.  882 castings so I wasn’t afraid of screwing them up.  I didn’t.   Now comes to putting the heads back together.  I got new valves and lifters (hydraulic) but I had planned to reuse the springs.  I was reading on here about the fellow with the SBC swapped 260Z who didn’t have the rocker arm tightened down enough and consequently his valves weren’t sealing.  The directions you folks supplied seemed easy enough to follow and I thought I understood it.  Then I started reading on some hot rod site (maybe HAMB) where everybody was saying that the installed height of the valve needed to be set via shimming to 1.7” + or - xxx.  What is that and how do you even measure the installed height of the spring?  Also, as it turns out, my valves aren’t even all the same height exactly.  

 

See fifth one from the left is shorter than the others.  There are a few that are shorter.  Is that going to be an issue?  I have no idea of the history of this engine. I can easily spring for new springs but if I don’t need to I won’t.  This will not be a race engine...unless some clown insists on racing in which case I’ll run it until it blows.   No idea what it’s going in.  I’d like to get a mid ‘80’s full-size van back dated to early ‘70’s.  

First:

 I was reading on here about the fellow with the SBC swapped 260Z who didn’t have the rocker arm tightened down enough and consequently his valves weren’t sealing.  

Rockers were tightened TOO MUCH, so the valves were not closing.

Second:

Then I started reading on some hot rod site (maybe HAMB) where everybody was saying that the installed height of the valve needed to be set via shimming to 1.7” + or - xxx.

The installed height is only changed when the seats and valve faces have been cut.  If the seats are new, and the valves are new, generally no shims required.  After machining, you need to replace the height lost to the valve being further down the port. The height is measured by installing the valves, retainers and keepers, and measuring from the retainer to the head.  There is a special micrometer available to make it easy and accurate, but if you are careful, you can get it close with a vernier caliper or two.

Third:

See fifth one from the left is shorter than the others.  There are a few that are shorter.  Is that going to be an issue?  

Yes.  Buy new springs, and pay real money.

New springs.  No point in skimping, especially because you have a different cam with different needs.  Many people assume that the spring rate corresponds to the RPM range.  This is not the case entirely.  It has more to do with lobe ramp profile and ramp speed.

As long as valve stem height (above the pocket) hasn't changed, shimming shouldn't be needed.

Pretty lady awkwardly shows you how to measure installed height with a tool

This is the right way to measure, and the tool isn't dreadfully expensive.

Let me bring this up again: I am pretty sure the 882 heads use two different valve spring heights. Shorter springs on the exhausts.

Do you happen to have 8 shorter springs in total?

In reply to SkinnyG :

I don’t know.  That’s a good point.  I’ll check tomorrow.