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I shim mine to meet the cam maker=E2=80=99s requirements, and usually =
find there is a range of a few shims within which they are all set the =
same. I also find that after two seasons the springs have lost about 30 =
lb seat pressure. I routinely rev my GT6 to 7k (same valve train as =
your Spit) and figured out that at a typical race weekend at Summit =
Point it might go to redline 560 times (about eight times a lap). your =
results may vary!
Anyway, a 30 lb loss is over 10%. My settings are roughly 60 lb closed, =
230 lb open at 0.523 lift. I run the Isky VWE 005/SP116. They also =
make a set with a softer inner spring (SP006) if you don=E2=80=99t need =
as much spring pressure.
I have a fairly radical cam, and these springs are adequate, have been =
running them for years. Other manufacturers offer what seem to be =
similar but not identical spec springs, but if you open up the box and =
they have orange paint on them, they are these Iskys. It seems others =
re-package and sell them. I=E2=80=99ve found this twice from other =
manufacturers, such as comp cams.
My guesses are:
you may not routinely run over 7k and have not noticed this before.
It may be valve float
If it=E2=80=99s a recent change, look for a broken valve spring
make sure your spring loads match the cam maker=E2=80=99s requirements.
If you have been running these springs =E2=80=9Cforever=E2=80=9D, =
replace them. They are a wear item.
See you at Pitt race!
On Jul 10, 2021, at 10:07 AM, ralph hansen via Fot <fot@autox.team.net> =
wrote:
I always set mine up with equal pressures at full closed. I would check =
them at full open and sometimes adjust them a bit to get better balance =
when closed. The pressure to open is more critical (told by a very old =
race tech from back in the day) to balance and smooth out the running at =
high rpm. Think of it as running through a series of eight spring loaded =
closed doors. If they are all the same spring pressure you fly through, =
with spring variances you get through some quicker, others impede your =
movement. I usually ended up with eight different shim stacks under my =
valves to achieve this but my under-developed 1147 would pull to 8k nice =
a steady and run a few ticks off the flyboys and ahead of many stronger =
cars.=20
On Saturday, July 10, 2021, 08:48:40 AM CDT, marty sukey via Fot =
<fot@autox.team.net> wrote:
Hey all. I am trying to decipher some power loss weirdness I was =
experiencing on the dyno Thursday over 7000 rpm on my Spitfire. One of =
the paths I am going down is valve spring pressure at full open. I know =
its cam dependent but what are some of you other Spitfire folks running =
so I can get some ballpark ideas. Heading to PittRace on Wednesday.=20
Thanks,
Marty
_______________________________________________
http://www.fot-racing.com <http://www.fot-racing.com/>
<http://www.team.net/donate.html>
Archive: http://autox.team.net/archive =
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Content-Transfer-Encoding: quoted-printable
charset=utf-8
<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; line-break: after-white-space;" class=3D"">I =
shim mine to meet the cam maker=E2=80=99s requirements, and usually find =
there is a range of a few shims within which they are all set the same. =
I also find that after two seasons the springs have lost about 30 =
lb seat pressure. I routinely rev my GT6 to 7k (same valve train =
as your Spit) and figured out that at a typical race weekend at Summit =
Point it might go to redline 560 times (about eight times a lap). =
your results may vary!<div class=3D""><br class=3D""><div =
class=3D"">Anyway, a 30 lb loss is over 10%. My settings are =
roughly 60 lb closed, 230 lb open at 0.523 lift. I run the Isky =
VWE 005/SP116. They also make a set with a softer inner spring =
(SP006) if you don=E2=80=99t need as much spring pressure.</div><div =
class=3D"">I have a fairly radical cam, and these springs are adequate, =
have been running them for years. Other manufacturers offer what =
seem to be similar but not identical spec springs, but if you open up =
the box and they have orange paint on them, they are these Iskys. =
It seems others re-package and sell them. I=E2=80=99ve found =
this twice from other manufacturers, such as comp cams.</div><div =
class=3D""><br class=3D""></div><div class=3D"">My guesses =
are:</div><div class=3D""><ul class=3D"MailOutline"><li class=3D"">you =
may not routinely run over 7k and have not noticed this before.</li><li =
class=3D"">It may be valve float</li><li class=3D"">If it=E2=80=99s a =
recent change, look for a broken valve spring</li><li class=3D"">make =
sure your spring loads match the cam maker=E2=80=99s =
requirements.</li><li class=3D"">If you have been running these springs =
=E2=80=9Cforever=E2=80=9D, replace them. They are a wear =
item.</li></ul><div class=3D""><br class=3D""></div><div class=3D"">See =
you at Pitt race!</div><div><br class=3D""><div class=3D"">On Jul 10, =
2021, at 10:07 AM, ralph hansen via Fot <<a =
href=3D"mailto:fot@autox.team.net"; class=3D"">fot@autox.team.net</a>> =
wrote:</div><br class=3D"Apple-interchange-newline"><div class=3D""><div =
class=3D""><div class=3D"ydp359c3cd6yahoo-style-wrap" =
style=3D"font-family: Helvetica Neue, Helvetica, Arial, sans-serif; =
font-size: 13px;"><div class=3D""></div>
<div dir=3D"ltr" data-setdir=3D"false" class=3D"">I always set =
mine up with equal pressures at full closed. I would check them at full =
open and sometimes adjust them a bit to get better balance when closed. =
The pressure to open is more critical (told by a very old race tech from =
back in the day) to balance and smooth out the running at high rpm. =
Think of it as running through a series of eight spring loaded closed =
doors. If they are all the same spring pressure you fly through, with =
spring variances you get through some quicker, others impede your =
movement. I usually ended up with eight different shim stacks under my =
valves to achieve this but my under-developed 1147 would pull to 8k nice =
a steady and run a few ticks off the flyboys and ahead of many stronger =
cars. </div><div class=3D""><br class=3D""></div>
=20
</div><div id=3D"ydp4d4ec34dyahoo_quoted_6793605569" =
class=3D"ydp4d4ec34dyahoo_quoted">
<div style=3D"font-family:'Helvetica Neue', Helvetica, =
Arial, sans-serif;font-size:13px;color:#26282a;" class=3D"">
=20
<div class=3D"">
On Saturday, July 10, 2021, 08:48:40 AM CDT, marty =
sukey via Fot <<a href=3D"mailto:fot@autox.team.net"; =
class=3D"">fot@autox.team.net</a>> wrote:
</div>
<div class=3D""><br class=3D""></div>
<div class=3D""><br class=3D""></div>
<div class=3D""><div id=3D"ydp4d4ec34dyiv9492892091" =
class=3D"">
=20
<div dir=3D"ltr" class=3D"">
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: =
12pt;" class=3D"">
Hey all. I am trying to decipher some power loss weirdness I was =
experiencing on the dyno Thursday over 7000 rpm on my Spitfire. One of =
the paths I am going down is valve spring pressure at full open. I know =
its cam dependent but what are some of you other
Spitfire folks running so I can get some ballpark ideas. Heading to =
PittRace on Wednesday. </div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: =
12pt;" class=3D"">
<br class=3D"">
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: =
12pt;" class=3D"">
Thanks,</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: =
12pt;" class=3D"">
Marty</div>
</div>
</div>_______________________________________________<br class=3D""><a =
href=3D"mailto:fot@autox.team.net"; rel=3D"nofollow" target=3D"_blank" =
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</div></div>_______________________________________________<br =
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class=3D"">fot@autox.team.net</a><br class=3D""><br =
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