Where do we pick up shims? I need .030's for 124lb seat pressure.

 

Summit and Jeg's carry them.

 

I got a set of Comp hardened shims from Summit.

FWIW, my Crane dual valve springs are shimmed .060" for use with the Crane 1.80 Quick-Lift rocker arms I'm using.

 

0.030" is a nasty thick shim.

I don't believe it's good practice to install such a heavy shim when it cuts
into bind clearanace and spring harmonics.

If one, or two valves are out by 0.030", you might want to shoot the tech
that did the valve job.

If all of the valves need that much shimming, you would be better off to change the
install height, and cross reference a spring with similar open height pressure.

Of course, this is my opinion.

 

When I installed my Crane '832's, the Crane spring seat locator caused my installed height to be 1.760 and my seat pressure was 125#. The locator acts as a shim so you really don't need to go looking for shims. The locator part number is 144460-16 and I had to use 2001 valve guide seals with the locator. My truck is an 03 Tahoe with a 5.3.

 

Where are you getting your info? Standard shims come in .060, .030 and sometimes .015 for trimming pressures. It is generally accepted practice that springs can safely be shimmed to .090 if there are no coil bind issues. The inconsistancies from spring to spring require shimming if you are going to do a valve job correctly. I agree that the stem height above the spring seat should be recorded for each valve during disassembly and that the stem height should be ground so that all heights are within .005" at reassembly; but that does not eliminate the need to check each spring for tension and shim to get each spring at proper seat pressure. Virtually every service manual, engineering text, and automotive service text state that as a rule of thumb a .030" shim should be used with new springs after a valve job (due to the higher placement of the retainer from grinding the seat and/or valve face) and a .060" shim should be used if reusing the original springs. Sometimes Ford has not recommended a .060 shim, but that is because they were running the OE spring within .060 of coil bind. GM doesn't do this. Don't know where your getting your info, but I think you need to check things out. .030" is not a lot of shim!!!

 

PS: Didn't you read what Mark Campbell wrote above. Shims have no affect on spring harmonics. If you need, I can refer you to several SAE papers that will corroborate his statement!!!

 

I'd like to read that study.

How can a spring that is slightly compressed have the same harmonics as
a spring sitting at full install height?

The dynamics are already different from the start.

 

It's the basic physics of coil spring design. Take a spring that has a rate of 350#/in and the installed height is 1.800 and the seat pressure is 110#. If you put a .030 shim under the spring the effective installed height changes to 1.770 and the seat pressure increases 10.5#(.030in x 350 #/in =10.5# of force...) but the rate doesn't change at all, it still is 350#/in. If you don't understand this basic concept of coil springs, STEP AWAY FROM THE WRENCH!! As far as wanting to see the study, I suggest you read some basic auto repair manuals first!! The same laws apply to coil springs in chassis too!!

 

If you are really serious about wanting to learn get "The Internal Combustion Engine, Theory and Practice" by Charles F.Taylor and published by MIT Press or get a copy of "The Internal Combustion Engine" by Sir Harry Ricardo. The latter was originally published in 1927, but upon reading it you will find that nothing much is new in the internal combustion engine. It's for sure that the physics of coil springs hasn't changed... they even had "beehives" back then!!

 

The "nasty thick" .030" shim has been in common use for decades and so has the, God Forbid, .060" shim.

The shim set that Comp Cams sells comes with 16 shims each (48 total) in .015", .030", and .060" thicknesses. These are the same standard thicknesses that have been used forever.

http://store.summitracing.com/partde...=KeywordSearch

 

What does that have to do with harmonics? OK, so the rate to close the spring doesn't change. But what about the clearance to allow for
rarefaction at open height? Wouldn't you be a little worried cutting into
the clearance by 0.030" @ 6200 RPM?


If I'm using a 0.030 to 0.060" shim in my valve train, I question the quality
of the valve work or spring.

I understand the need to shim springs to get the correct pressure. Don't
misread what I'm stating. I have shims under my springs as well.

What you both are misunderstanding is...0.030" correction for a spring is out
of spec.

If all of the springs are installed at 1.8" and ONE, or TWO springs need a 0.030"
shim to correct the pressure @ 1.770" ...don't you think those springs need to be
swapped out?

That's not the part that bugs me, it's the fact that coil bind comes sooner
and the clearance window is totally off.


OR

If all of the springs are isntalled at 1.8", and ONE, or TWO need 0.030" + shims
to correct a crappy valve job, you'd be happy with that? Sure the springs
are all at 1.8" again, but I'd be handing the heads back to the tech and
get some new valve seats installed at his expense.

Unless you like variance in combustion chamber volume

 

All you are proving by your comments and questions is that you do not have much experience doing cylinder head work or engine building. Please take the time to study a basic physics book on the chapters of coil spring design or contact the SAE at www.sae.org and get at couple of texts explaining springs. Then we can have an intelligent discussion. As it is; just because you don't understand the basic principles doesn't mean that the physics that makes the world go 'round is wrong. Have a safe weekend!! Q/T

 

I think you need to read your books again, or maybe get into working on
cylinder heads instead of trying to apply what you read...to something
you don't quite understand.

Everything in my reply is solid.

If you think adding a 0.030" shim is normal, I question your understanding
of machine work and tolerances. Either that, or the spring selection is way
off.

 

To meet my correct installed height I shimmed my 832's .090 all around

I have absolutely no worries as I know it is setup right.

 

We're not talking about install height for shims, but rather, shimming for
pressure (at least I am).

In all fairness, I re-read the post from top to bottom, and I see that the
discussion refers to another revision of spring on the lower half of the first
page.

What started out as an opinion (Post #24), has turned into a battle.

If you need to shim to get the install height - fine.

If you need to shim to get pressures:

a. Do you have the best suited spring?

b. Are you sacrificing clearance, or spring characteristics?

My position to clarify once again:

A 0.030" correction shim is out of spec IMO. A spring that sits at 1.770" with
125 lbs. seat pressure has a different spring rate than a spring that sits at
1.800" with 125 lbs. seat pressure.

The harmonics throughout each spring in the above scenario will be different.

I would not want a few of my springs shimmed at 0.030" or more, where the
others are at full install height.

As for shimming all springs for seat pressure, I would much rather install an
offset lock, or retainer ... or select another spring before I cut my open
height and clearance by 0.030"

Again, this is my opinion. It's an alternative to setting up a valve train
for correct pressures while leaving enough clearance for high RPM use.

 

Sorry Sir but the whole point of shimming a valvespring is to obtain the correct pressure. Your post makes me even more confident in the strength of the LS1 engine, as so many people do so many different things to them.

 

You think so? I guess that's why they have hundreds of different springs
then...not one size fits all with shimming?

I would think shimming is to balance the entire train pressures.

In any case...to each their own.

 

I didn't know the LS(x) engine has hundreds of different springs available?

Maybe you can point me towards this magical mountain of springs.

 

I typed in "LS1 valve spring" in Google and came up with over 11,800 hits.

I'm sure there's a few different MFG's and spring types to choose from.

Even if those aren't enough, you can always machine the heads to accept
a wider range of spring.