C7 LT1 Valve Spring Rate
Thread Starter
Burning Brakes
Joined: Jun 2012
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From: NJ
C7 LT1 Valve Spring Rate
Does anyone know what the valve springs specs are for the Gen V LT1 & LT4? So far I found the Spring height 1.90". I'm trying to find the spring rate.
Please Help
Thanks[/QUOTE]
Please Help
Thanks[/QUOTE]
Last edited by phantom1; Jul 13, 2020 at 05:13 PM.
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Thread Starter
Burning Brakes
Joined: Jun 2012
Posts: 1,024
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From: NJ
I searched everywhere and I could not find an answer. Only 2 places I can think of that may have an answer. There is @FYREANT here on the forum or you can maybe contact a speciality engine builder like WeaponX in Ohio. Try those.
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Search is your friend.
See my thread https://www.corvetteforum.com/forums...rear-axle.html ... I uploaded a spreadsheet in that thread (post #30), that included tons of spring rates.
THAT SAID, I do not have a spring tester available to me, and so I have not tested a stock/OEM "yellow stripe" or "blue stripe" spring. I do have several available ...
See my thread https://www.corvetteforum.com/forums...rear-axle.html ... I uploaded a spreadsheet in that thread (post #30), that included tons of spring rates.
THAT SAID, I do not have a spring tester available to me, and so I have not tested a stock/OEM "yellow stripe" or "blue stripe" spring. I do have several available ...
Last edited by AEK; Jul 14, 2020 at 12:34 AM.
Intermediate
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LT1 springs are 1.870" installed height intake and exhaust
Intake seat pressure - 113lbs
Exhaust seat pressure - 116lbs
Intake open pressure - 323lbs
Exhaust open pressure - 310lbs
LT4 springs are 1.800" intake installed height and 1.870" exhaust installed height
Intake seat pressure - 139lbs
Exhaust seat pressure - 115lbs
Intake open pressure - 331lbs
Exhaust open pressure - 328lbs
This is using stock LT1 and LT4 cam lift specs for open pressures and OEM installed heights.
I just measured these this morning.
Intake seat pressure - 113lbs
Exhaust seat pressure - 116lbs
Intake open pressure - 323lbs
Exhaust open pressure - 310lbs
LT4 springs are 1.800" intake installed height and 1.870" exhaust installed height
Intake seat pressure - 139lbs
Exhaust seat pressure - 115lbs
Intake open pressure - 331lbs
Exhaust open pressure - 328lbs
This is using stock LT1 and LT4 cam lift specs for open pressures and OEM installed heights.
I just measured these this morning.
Intermediate
Joined: Feb 2008
Posts: 26
Likes: 8
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Instructor
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Thanks!
Yes, LT1 and LT4 springs should be the same ... LT4 uses different valve(s) with different keeper/lock groove locations (I think), I presume mainly to handle the additional pressure on the face of the intake valve due to boost
Yes, LT1 and LT4 springs should be the same ... LT4 uses different valve(s) with different keeper/lock groove locations (I think), I presume mainly to handle the additional pressure on the face of the intake valve due to boost
Thread Starter
Burning Brakes
Joined: Jun 2012
Posts: 1,024
Likes: 88
From: NJ
Search is your friend.
See my thread https://www.corvetteforum.com/forums...rear-axle.html ... I uploaded a spreadsheet in that thread (post #30), that included tons of spring rates.
THAT SAID, I do not have a spring tester available to me, and so I have not tested a stock/OEM "yellow stripe" or "blue stripe" spring. I do have several available ...
See my thread https://www.corvetteforum.com/forums...rear-axle.html ... I uploaded a spreadsheet in that thread (post #30), that included tons of spring rates.
THAT SAID, I do not have a spring tester available to me, and so I have not tested a stock/OEM "yellow stripe" or "blue stripe" spring. I do have several available ...
Were you able to find out the stock spring rate?
Last edited by phantom1; Jul 15, 2020 at 01:27 PM.
Thread Starter
Burning Brakes
Joined: Jun 2012
Posts: 1,024
Likes: 88
From: NJ
LT1 springs are 1.870" installed height intake and exhaust
Intake seat pressure - 113lbs
Exhaust seat pressure - 116lbs
Intake open pressure - 323lbs
Exhaust open pressure - 310lbs
LT4 springs are 1.800" intake installed height and 1.870" exhaust installed height
Intake seat pressure - 139lbs
Exhaust seat pressure - 115lbs
Intake open pressure - 331lbs
Exhaust open pressure - 328lbs
This is using stock LT1 and LT4 cam lift specs for open pressures and OEM installed heights.
I just measured these this morning.
Intake seat pressure - 113lbs
Exhaust seat pressure - 116lbs
Intake open pressure - 323lbs
Exhaust open pressure - 310lbs
LT4 springs are 1.800" intake installed height and 1.870" exhaust installed height
Intake seat pressure - 139lbs
Exhaust seat pressure - 115lbs
Intake open pressure - 331lbs
Exhaust open pressure - 328lbs
This is using stock LT1 and LT4 cam lift specs for open pressures and OEM installed heights.
I just measured these this morning.
Thanks for the info.
Banned Scam/Spammer
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From: Stockton, ca
The yellow ones have to be stronger 
It is sad that trying to find a stronger easy drop in spring has to be a pain after 6 years. That was one of the good mods I had done to my stang after the SC install. Now my Vett is a ticking time bomb.
It is sad that trying to find a stronger easy drop in spring has to be a pain after 6 years. That was one of the good mods I had done to my stang after the SC install. Now my Vett is a ticking time bomb.
Thread Starter
Burning Brakes
Joined: Jun 2012
Posts: 1,024
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From: NJ
I found a few springs that I like, but they're all 1.80" install height. I found shims that will fit, I'm just concerned will that cause any issues. My first choice would be:
1. PSI-1511ML
2. PAC-1219X
1. PSI-1511ML
2. PAC-1219X
Last edited by phantom1; Oct 12, 2020 at 05:29 PM.
Instructor
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It would (probably) work if shims that matched the available ID (that is increased due to the one-piece valve stem seal's OD) were available ... but all the shims I have seen are designed around standard valve guide diameters, or the valve guide boss diameter ... these are all smaller IDs than the valve stem seal OD. What you want/need is a shim that is designed with a larger ID to match the valve stem seal's larger OD, and that is something that the aftermarket doesn't seem to want to support.
The 1.870" installed height of the LT1 is greater than 1.800", so with the right shims you could achieve an installed height of 1.800", yes.
Going by the measured numbers earlier in this thread, the spring compresses 0.551" (the lift of the LT1 cam on the intake (and exhaust, IIRC) for a change in pressure of 210 bs (323lbs - 113lbs), for a spring rate of 381lbs/in or roughly 385lbs as you surmise.
I do not know if the cam lift is specified at the valve, or at the cam -- I think it's at the valve, so we can ignore the rocker arm ratio.
The 1.870" installed height of the LT1 is greater than 1.800", so with the right shims you could achieve an installed height of 1.800", yes.
Going by the measured numbers earlier in this thread, the spring compresses 0.551" (the lift of the LT1 cam on the intake (and exhaust, IIRC) for a change in pressure of 210 bs (323lbs - 113lbs), for a spring rate of 381lbs/in or roughly 385lbs as you surmise.
I do not know if the cam lift is specified at the valve, or at the cam -- I think it's at the valve, so we can ignore the rocker arm ratio.
Last edited by AEK; Jul 15, 2020 at 08:07 PM. Reason: Corrected some stupidity on my part.
Instructor
Joined: Mar 2018
Posts: 233
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That picture of the valve stem seal standing alone illustrates the issue nicely -- compare its OD down at the bottom, to the OD of the "naked" valve guide to the right in that picture ... it's bigger than the guide's, and so you need shims with larger IDs to fit ... plus, the guide does not have any machined-in features to capture the valve stem seal, so you will be relying on friction alone to keep the seals on the guides if you toss the stock integrated seats/seals ...
And yes, PAC1215 was my main choice for a replacement spring.
And yes, PAC1215 was my main choice for a replacement spring.
Last edited by AEK; Jul 15, 2020 at 08:13 PM.