LS3 Intake Valve Stem length/height?
 

I'm building a L92 out of a 2007 Escalade for my Camaro.

I bought hollow LS3 Intake Valves to replace the solid L92 ones per the advise on this site, I got caught up with installing the Springs.....Measuring Installed height etc etc. & didn't notice that the Intake Stems are taller than the Exhaust Stems by about .020" until the heads were torqued down.

My PAC Springs came with an extra keeper/lock, With it on an original L92 Intake valve......Sure enough, The LS3 Valve is .020" taller from the Keeper Groove to the Tip.
I put a straight edge across a junk L92 head & all the Stems are the same height.

I was pretty confused at this point, So I took a Valve Cover & Rockers off a 2013 LS3 with 0821 heads & the Intake Valves are also .020" taller.......

WTF?? What do I do here? I know this will throw off lifter preload, Is it common to run 2 different length pushrods on a LS3??

Pic of the stock LS3.....
Attachment 594854

It's fine. The LS6 hollow stems are like that too. It's not going to throw off the lifter preload enough to matter either.

Unless you are running short travel lifters, the plunger should take up the difference without ill-effect.

Yep. Measure for pushrod length and run it.

The stock ls3 pics should tell you something. ...I think your heads are fine and your sweatin over nuthin'......I noticed the same thing when I built my first ls....ran with the original pushrods on an asa cam with no issues. ...but yea when I noticed the valvestem heights too I was concerned but upon more research I found it to be normal and ran with it.....don't fry your brain trying to figure these engines out....they are quite simple! !!

I don't care if this is 3yrs old btw....

Better late than never....in some cases...maybe not this one!

We can already see the butt hurt people .....nothing better to do than monitor the dates of stuff and get there panties in a bunch!!!!!...can't we all just get along

this was never quoted on this thread....you copied and dragged this from your butthole

I only see one, It is funny to see someone answer a persons tech question that was most likely resolved years ago... It's kind of like a guy saying hey if I jump out of this building tomorrow will I die.... What's the point of answering the day after he jumped?

Zombie thread! ;) Those taller LS3 hollow stem valves puzzled me, too, when I built my engine a couple of years ago. I found one article in an old journal that seemed to explain it. When GM spec-ed the higher performance LS6 variant, they increased intake valve lift, reduced the base circle of that cam lobe, and made the intake valve correspondingly taller, all so they could use the same pushrods and maintain equal lifter preload. The author of that article said the longer valve minimized the number of other parts that needed to change. For my build I ordered different length pushrods from Manton to keep my lifter preload the same across all of the valves.

Preload would be corrected but geometry will be out of spec. All stem heights must be the same, otherwise the pedestal height will need to be adjusted for the difference. You can also go with adjustable rockers or remove the .020 from the top of the stem.

Yes the lengths are different between the LS3 and L92 intake valves and running a same length pushrod on a lifter that likes 0.010 preload would be a problem when running a stock rocker arm. The top of the valves on the L92 or 823 cylinder heads all line up but the LS3 or 821's which have the hollow stem valves do not. The reason you can run a same length pushrod is because the lifters have enough preload range to allow for the .020-.025 difference. Is there anything else somebody would like to add to close the book on this thread!

The only thing this affects is the spring pressure since you're changing the installed height.

Geometry is unaffected on the stock rockers since they are not shaft mounted. And they are sloppy to begin with. You can't center them since they slide over the valve like a rocking chair anyway.

Pushrod length can adjust for any additional preload that may be introduced.

Etc. etc.

Actually the groove between the two valves are the same so spring height is the same. The difference is the height of the stem above the groove in the valves where the keepers sit.