Valve Spring Installed Height 1.900 ????
04-01-2012, 08:04 AM
#1
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Valve Spring Installed Height 1.900 ???? Not sure if i can shim these springs this much or if something is wrong. I am putting a set of pac racing 1518 valve springs onto a stock untouched set of 243 LS6 heads. I am using pac spring seats, locks and retainers.
Yesterday i measured the installed height and i am just over 1.900. Pac says to install at 1.800. This seems like to much to shim but i am still new at this. Any ideas?
Here are some pics
Yesterday i measured the installed height and i am just over 1.900. Pac says to install at 1.800. This seems like to much to shim but i am still new at this. Any ideas?
Here are some pics
04-01-2012, 08:23 AM
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Looks to me like the seat is under the tool. Stock height is around 1.8 or so, so something is off. I remember setting up my Lunati duals and they came out to 1.81.
04-01-2012, 09:13 AM
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04-01-2012, 09:22 AM
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04-01-2012, 09:24 AM
#7
Installing at 1.8 gives the pressures listed from the manufacturers...
installing at a taller height will give less pressures open and closed...
to get the proper spring pressures and seat pressures...you need to add a shim and instal at the recommended height...
leaving it at 1.9 can allow the lack of pressures to cause valve float and lack of proper valve control.
as long as the coil bind at installed height is less than your lift, then you can shim it up as far as you need to.
example... coil bind at 1.1
install at 1.8
max lift = .700...typically it will say spring good to .650
and I also like to follow the .50 from bind rule that most manufacturers put on their springs.
same spring.. if installed at 1.9 will have the same coil bind at 1.1... but that will allow for .750 lift or it will say good to .700 and will have less open and closed pressure than if installed at 1.8 by adding a shim.
conversely... shimming a spring to be at a lower installed height will increase pressures...which can also be useful on a low lift cam with a spring with a lot of travel before coil bind.
installing at a taller height will give less pressures open and closed...
to get the proper spring pressures and seat pressures...you need to add a shim and instal at the recommended height...
leaving it at 1.9 can allow the lack of pressures to cause valve float and lack of proper valve control.
as long as the coil bind at installed height is less than your lift, then you can shim it up as far as you need to.
example... coil bind at 1.1
install at 1.8
max lift = .700...typically it will say spring good to .650
and I also like to follow the .50 from bind rule that most manufacturers put on their springs.
same spring.. if installed at 1.9 will have the same coil bind at 1.1... but that will allow for .750 lift or it will say good to .700 and will have less open and closed pressure than if installed at 1.8 by adding a shim.
conversely... shimming a spring to be at a lower installed height will increase pressures...which can also be useful on a low lift cam with a spring with a lot of travel before coil bind.
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04-01-2012, 09:38 AM
#8
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Installing at 1.8 gives the pressures listed from the manufacturers...
installing at a taller height will give less pressures open and closed...
to get the proper spring pressures and seat pressures...you need to add a shim and instal at the recommended height...
leaving it at 1.9 can allow the lack of pressures to cause valve float and lack of proper valve control.
as long as the coil bind at installed height is less than your lift, then you can shim it up as far as you need to.
example... coil bind at 1.1
install at 1.8
max lift = .700...typically it will say spring good to .650
and I also like to follow the .50 from bind rule that most manufacturers put on their springs.
same spring.. if installed at 1.9 will have the same coil bind at 1.1... but that will allow for .750 lift or it will say good to .700 and will have less open and closed pressure than if installed at 1.8 by adding a shim.
conversely... shimming a spring to be at a lower installed height will increase pressures...which can also be useful on a low lift cam with a spring with a lot of travel before coil bind.
installing at a taller height will give less pressures open and closed...
to get the proper spring pressures and seat pressures...you need to add a shim and instal at the recommended height...
leaving it at 1.9 can allow the lack of pressures to cause valve float and lack of proper valve control.
as long as the coil bind at installed height is less than your lift, then you can shim it up as far as you need to.
example... coil bind at 1.1
install at 1.8
max lift = .700...typically it will say spring good to .650
and I also like to follow the .50 from bind rule that most manufacturers put on their springs.
same spring.. if installed at 1.9 will have the same coil bind at 1.1... but that will allow for .750 lift or it will say good to .700 and will have less open and closed pressure than if installed at 1.8 by adding a shim.
conversely... shimming a spring to be at a lower installed height will increase pressures...which can also be useful on a low lift cam with a spring with a lot of travel before coil bind.
04-01-2012, 09:41 AM
#9
I definately do not want to install at 1.9. That is the reason i started this thread. The cam has a lift of 634 so i want to make sure they are installed at the proper 1.800 height. So you are saying its ok to shim these the whole tenth? Correct me if i am wrong but with a .060 shim i will still come in at 1.840. So i would need more then 1 shim? Is that ok to do? Or am i completely missing something.
what is coil bind listed as on this spring?
you can shim as far as you want as long as you dont run into coil bind.
and I would stay .050 away from coil bind.
04-01-2012, 09:46 AM
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04-01-2012, 09:58 AM
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That particular spring height mic is not the proper one for our ls1's. The retainer has to sit on top of the mic not in the recess. Your going to have to measure the recess to the top of the mic and subtract it from your measured spring height. The proper one looks like this as you can see there is no recess. Its made specifically for beehive springs.
04-01-2012, 10:01 AM
#12
I think you may need a different spring...
1.800-1.140 = 0.660
I'm not saying you cant run that spring....
but I personally would not run that close to coil bind...
I would try to get a spring with a coil bind of 1.10 or a total of .700 from installed height
or atleast something with a coil bind closer to 1.10
lift of .634 means a spring that will handle .684...
I would be ok with one that lists install at 1.800 and coil bind at 1.125 or a total lift of .675
I think the PRC EHT springs might fit what you are looking for with a 1.8 install height
Specs:
Install Height: 1.800"
Closed Spring Pressure: 157lbs @ 1.800"
Open Spring Pressure: 471lbs @ 1.125"
Maximum Spring Lift: .675"
Coil Bind 1.060"
Spring Rate: 483lbs/in
1.800-1.140 = 0.660
I'm not saying you cant run that spring....
but I personally would not run that close to coil bind...
I would try to get a spring with a coil bind of 1.10 or a total of .700 from installed height
or atleast something with a coil bind closer to 1.10
lift of .634 means a spring that will handle .684...
I would be ok with one that lists install at 1.800 and coil bind at 1.125 or a total lift of .675
I think the PRC EHT springs might fit what you are looking for with a 1.8 install height
Specs:
Install Height: 1.800"
Closed Spring Pressure: 157lbs @ 1.800"
Open Spring Pressure: 471lbs @ 1.125"
Maximum Spring Lift: .675"
Coil Bind 1.060"
Spring Rate: 483lbs/in
Last edited by soundengineer; 04-01-2012 at 10:10 AM.
04-01-2012, 11:21 AM
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yup i just came off a broken 1518 with only .631 lift but the valve stayed up. They swear that these springs are a good fit for the new cam so i guess i'm trusting the experts. people say double save a valve but i've seen just as many dropped valves with duals as beehives so i guess we'll see
04-01-2012, 02:32 PM
#17
That particular spring height mic is not the proper one for our ls1's. The retainer has to sit on top of the mic not in the recess. Your going to have to measure the recess to the top of the mic and subtract it from your measured spring height. The proper one looks like this as you can see there is no recess. Its made specifically for beehive springs.
04-01-2012, 05:26 PM
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I just ordered the comp cams 4930 beehive micrometer. When that comes in, i will re measure and post the results and see where i am at with installed height.
I appreciate all the info and help!
As far as the spring choice i know i am border line on these springs for max lift. The cam was free and i already had the springs. After a call to pac racing they said they should work if installed properly so I decided to try them.
I appreciate all the info and help!
As far as the spring choice i know i am border line on these springs for max lift. The cam was free and i already had the springs. After a call to pac racing they said they should work if installed properly so I decided to try them.
