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Thanks to all of you for the usefull information.
35kgs seat pressure seem to be too low : with shimming, 50kgs/110lbs is
possible without risking coil binding and the nose pressure will then be
120kgs/265lbs. For the cylinderhead with 25kgs seat pressure, I've to look
for new springs.
I've been weighing the parts of the drive train :
Depending on what push rods are used, minimum weight is 380 g, maximum is
420g! ( half of the weight of the springs and the rockers is taken into
account). My heaviest 'race' pushrods are 130 g, the lightest are
still 90g. Standard pushrods are about 73 g : I wonder if these pushrods are
strong enough?
I forgot about the valve train for years, it's strange and maybe it's the
same for you , but I always have blind spots for some area's of my race car.
Marcel
_____
Van: Fot [mailto:fot-bounces@autox.team.net] Namens Enquiries Road & Track
Verzonden: woensdag 16 september 2015 22:24
Aan: fot@autox.team.net
Onderwerp: [Fot] re TR6 Cannon Intake Manifold
re valve seat pressures
valve seat pressures are normally considered as a pair, seat pressure and
nose pressure. more often than not, the cam grinder suggests what "over the
nose" pressure is probably needed and you then work backwards and find the
seat pressure.
you can make small alterations by shimming the bottom of the valve springs.
some brands of springs used to come with suggested shim thicknesses, but in
our engine shop we have a spring rate gauge to work this out
all of this needs some experimentation and definitely on a cam-by-cam basis.
generalist advice is often not helpful as it might seem
spring pressure is not the only consideration for valve float at high revs
so dont become fixated on this. valve train weight, spring interference
(inner to outer) and cam lobe ramp design, are all equally critical issues.
in days of old, very high pressures were used , often because the people
involved had no other method of controlling valve bounce at high revs.
today, analysis of working springs using a strobe light and some times high
speed video, ultra light weight valve gear, controlled inner/outer spring
interference, all combine to allow spring rates to fall dramatically on a
modern, highly accurately ground cam
on a TR6 with the stock "heavy" valves, pushrods & lifters, and an old
design cam something like 250lb over the nose is likely to be needed on a
wild race cam.
all of my engines run the lowest possible pressures and the lightest
possible valve train. we have got nose pressure down to 150lb on several TR6
race engines
Terry O'Beirne
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<DIV dir=3Dltr align=3Dleft><FONT color=3D#0000ff size=3D2 =
face=3DArial><SPAN=20
class=3D733074207-18092015>Thanks to all of you for the usefull=20
information.</SPAN></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN =
class=3D733074207-18092015></SPAN><SPAN=20
class=3D733074207-18092015></SPAN><FONT face=3DArial><FONT =
color=3D#0000ff><FONT=20
size=3D2>3<SPAN class=3D733074207-18092015>5kgs seat pressure seem =
to=20
be too low : with shimming, 50kgs/110lbs is possible without =
risking coil=20
binding and the nose pressure will then be 120kgs/265lbs. For the =
cylinderhead=20
with 25kgs seat pressure, I've to look for new=20
springs.</SPAN></FONT></FONT></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><FONT face=3DArial><FONT =
color=3D#0000ff><FONT size=3D2><SPAN=20
class=3D733074207-18092015> I've been weighing the parts of the =
drive train=20
:</SPAN></FONT></FONT></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN =
class=3D733074207-18092015></SPAN><SPAN=20
class=3D733074207-18092015></SPAN><FONT face=3DArial><FONT =
color=3D#0000ff><FONT=20
size=3D2>D<SPAN class=3D733074207-18092015>epending on what push rods =
are used,=20
minimum weight is 380 g, maximum is 420g! ( half of the weight of the =
springs=20
and the rockers is taken into account). My heaviest 'race' pushrods are =
130=20
g, the lightest are</SPAN></FONT></FONT></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN =
class=3D733074207-18092015></SPAN><SPAN=20
class=3D733074207-18092015></SPAN><FONT face=3DArial><FONT =
color=3D#0000ff><FONT=20
size=3D2>s<SPAN class=3D733074207-18092015>till 90g. Standard pushrods =
are about 73=20
g : I wonder if these pushrods are strong=20
enough?</SPAN></FONT></FONT></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN =
class=3D733074207-18092015></SPAN><SPAN=20
class=3D733074207-18092015></SPAN><FONT face=3DArial><FONT =
color=3D#0000ff><FONT=20
size=3D2>I<SPAN class=3D733074207-18092015> forgot about the valve train =
for years,=20
it's strange and maybe it's the same for you , but I always have =
blind=20
spots for some area's of my race car.</SPAN></FONT></FONT></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN =
class=3D733074207-18092015></SPAN><SPAN=20
class=3D733074207-18092015></SPAN><FONT face=3DArial><FONT =
color=3D#0000ff><FONT=20
size=3D2>M<SPAN=20
class=3D733074207-18092015>arcel</SPAN></FONT></FONT></FONT><BR></DIV>
<DIV lang=3Dnl class=3DOutlookMessageHeader dir=3Dltr align=3Dleft>
<HR tabIndex=3D-1>
<FONT size=3D2 face=3DTahoma><B>Van:</B> Fot =
[mailto:fot-bounces@autox.team.net]=20
<B>Namens </B>Enquiries Road & Track<BR><B>Verzonden:</B> woensdag =
16=20
september 2015 22:24<BR><B>Aan:</B> =
fot@autox.team.net<BR><B>Onderwerp:</B>=20
[Fot] re TR6 Cannon Intake Manifold<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=3Dltr>re valve seat pressures
<DIV><BR></DIV>
<DIV>valve seat pressures are normally considered as a pair, seat =
pressure and=20
nose pressure. more often than not, the cam grinder suggests what "over =
the=20
nose" pressure is probably needed and you then work backwards and find =
the seat=20
pressure.
<DIV><BR></DIV>
<DIV>you can make small alterations by shimming the bottom of the valve =
springs.=20
some brands of springs used to come with suggested shim thicknesses, but =
in our=20
engine shop we have a spring rate gauge to work this out<BR>
<DIV><BR></DIV>
<DIV>all of this needs some experimentation and definitely on a =
cam-by-cam=20
basis. generalist advice is often not helpful as it might seem</DIV>
<DIV><BR></DIV>
<DIV>spring pressure is not the only consideration for valve float at =
high revs=20
so dont become fixated on this. valve train weight, spring interference =
(inner=20
to outer) and cam lobe ramp design, are all equally critical =
issues. </DIV>
<DIV><BR></DIV>
<DIV>in days of old, very high pressures were used , often because the =
people=20
involved had no other method of controlling valve bounce at high revs. =
today,=20
analysis of working springs using a strobe light and some times high =
speed=20
video, ultra light weight valve gear, controlled inner/outer spring=20
interference, all combine to allow spring rates to fall dramatically on =
a=20
modern, highly accurately ground cam <BR>
<DIV><BR></DIV>
<DIV>on a TR6 with the stock "heavy" valves, pushrods & lifters, and =
an old=20
design cam something like 250lb over the nose is likely to be needed on =
a=20
wild race cam. </DIV>
<DIV><BR></DIV>
<DIV>all of my engines run the lowest possible pressures and the =
lightest=20
possible valve train. we have got nose pressure down to 150lb on several =
TR6=20
race engines </DIV>
<DIV><BR></DIV>
<DIV>Terry O'Beirne<BR>
<DIV>
<DIV=20
class=3Dgmail_signature><BR></DIV></DIV></DIV></DIV></DIV></DIV></DIV></B=
ODY></HTML>
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_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
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