Installed Valve Spring Height
Installed Valve Spring Height I installed a G5X3 LG Motorsports (comp) cam with PAC 1519 springs, seats and retainers in my otherwise stock LS1 with 241 heads. I am currently setting up my valve train and have a question for the more experienced. I am a fan of quality beehive springs and believe that if they are set up correctly will provide better performance than duals. I hope I am able to learn something here and not have this thread turn into a bash beehive session.
My spring height using the stock spring seat is reading 1.792 and utilizing the PAC spring seat is reading 1.772. I know that the spring pressure specifications are provided at a 1.8 installed height. I have read that static height readings are somewhat tighter than after they are ran - that when the engine starts the spring seats the retainer even further into the keeper an additional .010 - .020, causing a loss in spring pressure. The stock spring seats are getting extremely close to the recommended 1.8 installed height but it appears to me that I'd be better with the PAC seats if they actually settle. I also think it would be good to have a little more spring pressure due to the lobes on this cam. Thoughts?
I've also read that whenever in doubt about seat pressure run a little more and not a little less. Am I safer to assume I should use the thicker seats in this situation. Of course double checking coil bind also to make sure I have clearance. If I am figuring my math correctly it puts coil bind at .062. Is this correct and sufficient clearance?
Anybody have any experience and recommendation with this? Thanks for helping!
My spring height using the stock spring seat is reading 1.792 and utilizing the PAC spring seat is reading 1.772. I know that the spring pressure specifications are provided at a 1.8 installed height. I have read that static height readings are somewhat tighter than after they are ran - that when the engine starts the spring seats the retainer even further into the keeper an additional .010 - .020, causing a loss in spring pressure. The stock spring seats are getting extremely close to the recommended 1.8 installed height but it appears to me that I'd be better with the PAC seats if they actually settle. I also think it would be good to have a little more spring pressure due to the lobes on this cam. Thoughts?
I've also read that whenever in doubt about seat pressure run a little more and not a little less. Am I safer to assume I should use the thicker seats in this situation. Of course double checking coil bind also to make sure I have clearance. If I am figuring my math correctly it puts coil bind at .062. Is this correct and sufficient clearance?
Anybody have any experience and recommendation with this? Thanks for helping!
Last edited by high impact; Aug 5, 2013 at 12:50 PM.
spring specs:
150# at 1.800”
363# at 1.200”
.625” Max Lift
Coil Bind: 1.100"
75 grams
Can I simply double check that number by using a feeler gauge in between coils at full lift?
According to my math the thicker seats give me slightly over .060 coil bind. If I have this figured correctly... coil bind 1.1 plus .060 plus my actual highest lift .610 equals 1.77 for my final installed height. Appears I may be right on the ragged edge. Is there a tolerance since not every spring will be exact? Like =/- .010 or something like that? This also means I need to check every valve correct?
150# at 1.800”
363# at 1.200”
.625” Max Lift
Coil Bind: 1.100"
75 grams
Can I simply double check that number by using a feeler gauge in between coils at full lift?
According to my math the thicker seats give me slightly over .060 coil bind. If I have this figured correctly... coil bind 1.1 plus .060 plus my actual highest lift .610 equals 1.77 for my final installed height. Appears I may be right on the ragged edge. Is there a tolerance since not every spring will be exact? Like =/- .010 or something like that? This also means I need to check every valve correct?
Last edited by high impact; Aug 5, 2013 at 02:20 PM.
You must litteraly take each spring to solid height, this is your CB number. Add 0.060 to that number. Each one will be different. Now add the lift to that number. Now factor in every valve having a different installed height. Yes it gets to be a pain.
Nope. Coil bind is not 0.060 between each coil. CB clearence is the sum of 0.060 between all coils. Since most springs do ned deflect the same amount in each coil, especially beehives, you cannot simple use a feeler gauge.
You must litteraly take each spring to solid height, this is your CB number. Add 0.060 to that number. Each one will be different. Now add the lift to that number. Now factor in every valve having a different installed height. Yes it gets to be a pain.
You must litteraly take each spring to solid height, this is your CB number. Add 0.060 to that number. Each one will be different. Now add the lift to that number. Now factor in every valve having a different installed height. Yes it gets to be a pain.
That makes sense. PAC lists my springs coil bind at 1.1 so can I use that listed spec for all 16 springs? Is .060 a good margin? That means I am shooting for 1.77. What is my spring height tolerance?
Do you mean installed height or free height. You should be able to keep the installed height pretty close. I don't recall the exact numbers but mine were within +/- 0.010" installed height and may have actually been closer. I set everthing up in a spread sheet and monitored each valve set as I did them so I could look over both heads when I was done. In included clearance to coil bind and also clearance between the retainer and the valve seal, something that a few have overlooked and then hammered the seals when they ran the motor. Having a shim kit available my be required as well unless you are going just with the seat.
Also, with regards to seat value, having a little too much seat force won't kill a valve train but having too little could. I wouldn't worry about the 1.800" but rather the final seat force of the spring. I can't recall any of the heads I have worked on being at 1.800", they are always at a shorter installed height including stock heads.
Also, with regards to seat value, having a little too much seat force won't kill a valve train but having too little could. I wouldn't worry about the 1.800" but rather the final seat force of the spring. I can't recall any of the heads I have worked on being at 1.800", they are always at a shorter installed height including stock heads.
I have a related question: I have heads setup by TEA with PAC dual springs. If I remove the springs to install checker springs, and I reinstall the springs, should I recheck them? Or would simple removal of the retainer and spring and reinstallation cause a change in height?
Trending Topics
If you do not remove any shim the installed height should not change. With OE locks I do not know if this would be the case but any aftermarket machined lock will be identical (it should be at least).
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
