Valve spring shim installation
#1
Valve spring shim installation
I was always under the impression that the shims for the springs went under the valve spring seat. However, I have found them above the seat on my new heads. The seat is part of the one piece valve seal/seat. Does the location matter, since they won't fit below the seal/seat anyhow? I believe them to be the hardened shims from Comp.
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if they were thick shims then i would def put it under the spring to keep the shim from becoming another moving part that adds weight to your valvetrain.If they are thin then dont worry about it.They make shims to fit any heads in any size,just have to find them.
#5
Originally Posted by redtail2426
if they were thick shims then i would def put it under the spring to keep the shim from becoming another moving part that adds weight to your valvetrain.If they are thin then dont worry about it.They make shims to fit any heads in any size,just have to find them.
The springs are under the spring no matter what, on an LSx head. They are either under the spring and the seat/cup, or just under the spring and on top of the seat/cup...
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#9
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My shims went under my spring cups (Comp 921 springs, AFR 205 heads).
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
#12
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If you shim under the seat the seal will move up and off of the valve guide.
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Shims
First off we dont use the wrong parts when we assemble heads. Second it doesnt matter with that head either way because of the one piece seal/shim. 3rd take into consideration the fact if you shim under, one you move the seal up higher on the guide so you dont get all the grip, two it moves the seal closer to the bottom of the retainer. This obviously would cause a problem with retainer to seal interference and will decrease the gross lift that you could run, lets say it can normally handle .640 from seal to retainer, now you shim under the seal/shim with a .040 shim now it can only clear a .600 lift camshaft. See the dilemma.
Parts are machined with tolerances, and in some cases heads out there may use very little shim or none at all, and in this case it may be under, and still allow the head company to achieve the larger clearance range.
Intake and exhaust shims shouldnt necessarily match as the valve lengths are different from intake to exhaust on the LS heads, and also when you install springs you are setting up for peak lift, spring pressure for that lift point, and this is affected by installed height, so you might have .040 under some, .015 under some, none or .060 who knows, thats why professionals use spring height micrometers to measure, and shim accordingly!
You know Dart has a tech email address and can answer these questions correctly after all they build over 40,000 heads per year, who can be more qualified to answer these questions. darttech@dartheads.com
Parts are machined with tolerances, and in some cases heads out there may use very little shim or none at all, and in this case it may be under, and still allow the head company to achieve the larger clearance range.
Intake and exhaust shims shouldnt necessarily match as the valve lengths are different from intake to exhaust on the LS heads, and also when you install springs you are setting up for peak lift, spring pressure for that lift point, and this is affected by installed height, so you might have .040 under some, .015 under some, none or .060 who knows, thats why professionals use spring height micrometers to measure, and shim accordingly!
You know Dart has a tech email address and can answer these questions correctly after all they build over 40,000 heads per year, who can be more qualified to answer these questions. darttech@dartheads.com
Last edited by Dart331Stroker; 01-04-2006 at 11:15 AM. Reason: forgot dart email address
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Originally Posted by Dart331Stroker
First off we dont use the wrong parts when we assemble heads. Second it doesnt matter with that head either way because of the one piece seal/shim.
#17
Thanks for all the information Dart331Stroker. I have actually been in contact with Greg Wold with questions via e-mail (he probably thinks I am a pain by now ), but many times it is to the benefit of all here on LS1Tech to get correct information from the manufacturer and that is why I also posted here. I didn't see any other way the shims would fit correctly, but I also have never seen it done this way and my two LS1 books show them under the seat.
As for the seals, I have priced the GM one piece seal/seat and they are not cheap!!!! Good to know the seals are also quality parts
I did carefully remove them making sure I lubed up the seal before removal. I am assuming I can re-use them as they look perfect and I don't think they seal on the threaded portion of the guide anyhow.
As for the seals, I have priced the GM one piece seal/seat and they are not cheap!!!! Good to know the seals are also quality parts
I did carefully remove them making sure I lubed up the seal before removal. I am assuming I can re-use them as they look perfect and I don't think they seal on the threaded portion of the guide anyhow.
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Yep you can re-use them, as long as they're not damaged. Nope, you're not a pain. You have enough sense to ask questions before you do something, instead of after breaking parts.
As for the LS1 books, I'm not sure why they chose to put the shims underneath the seats. Like I said, you could do it that way, however, we prefer them over the seats, for the reasons mentioned above.
As for the LS1 books, I'm not sure why they chose to put the shims underneath the seats. Like I said, you could do it that way, however, we prefer them over the seats, for the reasons mentioned above.
#19
Greg,
Thanks, I think I sent this to you in an e-mail, it appears that the Dart heads are shimmed so all the seat pressures are the same. Is there an advantage/disadvantage to putting a little more pressure under the heavier intake valve, or is it more important to have consistant pressure on all 16?
Thanks, I think I sent this to you in an e-mail, it appears that the Dart heads are shimmed so all the seat pressures are the same. Is there an advantage/disadvantage to putting a little more pressure under the heavier intake valve, or is it more important to have consistant pressure on all 16?