<html><body><div style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt; color: #000000"><div><br></div><div>Larry, you say most camshafts smack the lifters hard. Will a smaller valve clearance relieve this a bit? Has it disadvantages to set the clearance smaller than recommended?(except that the valves will run hotter)</div><div>Marcel</div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>Van: </b>"fot" <fot@autox.team.net><br><b>Aan: </b>"fot" <fot@autox.team.net><br><b>Verzonden: </b>Woensdag 19 februari 2020 22:14:38<br><b>Onderwerp: </b>Re: [Fot] Camshaft recommendation<br></div><div><br></div><div data-marker="__QUOTED_TEXT__">I agree with much of what Richard says. The problem with the TR6
engine is it has a tiny 0.8" diameter lifter, so as Richard says the
higher ratio rocker can help to overcome this limitation. As you
mention, one wants a quick opening (and closing). That means high
acceleration. Remember Newton's law F = ma? What most people don't
realize is that the rocker ratio's effect on the forces is squared:
(1.65/1.5)^2 = 1.21. So the valves and valve springs are effectively
20% heavier. Ideally, to do it properly you would develop a grind
for the specific rocker ratio. That being said, from measuring a
number of after market cams, I've found most are not particularly
aggressive in terms of the acceleration, but many smack the lifter
hard initially and slam the valve back down on the seat (high ramp
velocity), which can cause valve bounce and other problems. You can
find a bit more discussion at my website -
<a href="http://tildentechnologies.com/Cams/CamSprings.html" target="_blank" rel="nofollow noopener noreferrer">http://tildentechnologies.com/Cams/CamSprings.html</a>.<br>
<br>
Another point. I think people get hung up on valve lift. After all,
the valve is at maximum lift for an infinitesimal time. I suggest
you look at the duration the valve is open at intermediate lifts of
say 0.20. To avoid losing the low end, you want to do this without
excessively large seat-to-seat duration. For a given seat-to-seat
(or 0.050) duration, there is no downside to more lift, since it
usually produces more duration at intermediate lifts.<br>
Cheers,<br>
Larry Young<br>
<br>
<div class="moz-cite-prefix">On 2/12/2020 12:19 PM,
van.mulders.marcel--- via Fot wrote:<br>
</div>
<blockquote>
<div style="font-family:'verdana' , 'arial' , 'helvetica' , sans-serif;font-size:10pt;color:#000000">
<div><br>
</div>
<div>Richard,</div>
<div>dare I answer again...</div>
<div>You say :" first decide what will be the optimum lift for
your engine , then... ": in that case : what is the point of
high ratio rocker arms, if you want to end at the same maximum
valve lift? With a higher lobe x lower rocker ratio, the valve
opening speed will be the same and you have a lower force
(load) at the pushrods and lobe/cam followers. I think the
only reason for a higher rocker ratio is the camfollowers
having a too small a diameter to be able to get at the maximum
valve lift you want?</div>
<div>Marcel</div>
<hr id="zwchr">
<div><b>Van: </b>"Richard Good"
<a href="mailto:goodparts@verizon.net" target="_blank" rel="nofollow noopener noreferrer"><goodparts@verizon.net></a><br>
<b>Aan: </b>"van mulders marcel"
<a href="mailto:van.mulders.marcel@telenet.be" target="_blank" rel="nofollow noopener noreferrer"><van.mulders.marcel@telenet.be></a><br>
<b>Cc: </b>"fot" <a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer"><fot@autox.team.net></a><br>
<b>Verzonden: </b>Woensdag 12 februari 2020 17:25:10<br>
<b>Onderwerp: </b>Re: [Fot] Camshaft recommendation<br>
</div>
<div><br>
</div>
<div>
<p dir="ltr">Marcel,</p>
<p dir="ltr">Yes, if you increase rocker ratio and do not
change the cam lift, the maximum lift will also increase by
13%.</p>
<p dir="ltr">Richard</p>
<p dir="ltr">Sent from AOL Mobile Mail <br>
Get the new AOL app: mail.mobile.aol.com</p>
<hr style="border:0;height:1px;color:#999;background-color:#999;width:100%;margin:0 0 9px 0;padding:0"><span style="font-size:14px;color:#999999">On Wednesday, February
12, 2020 van.mulders.marcel <<span style="color:#0000a0"><a href="mailto:van.mulders.marcel@telenet.be" target="_blank" rel="nofollow noopener noreferrer">van.mulders.marcel@telenet.be</a></span>>
wrote:</span><br>
<div>
<div style="font-family:'verdana' , 'arial' , 'helvetica' , sans-serif;font-size:10pt;color:#000000">
<div>Richard, </div>
<div>dare I answer this...</div>
<div>Do you mean that, with the higher rocker ratio, the
valve is moving faster in the first part of the opening
phase and hence moving slower nearing the maximum lift?
Suppose the cam lift of both camshafts is such that the
maximum lift is 13mm for both the 1.65 and 1.50 ratio
and duration at 0.050" is 240°, thus the crank has to
move 120° to go from 0.050" lift to maximum lift in both
cases. If the valve is opening 13% faster all the way
from 0.050" lift untill maximum lift, the maximum lift
will also be 13% higher! When an engine is at, say
5000rpm or any other speed, it takes the same time to
move 120° (from 0.050" to maximum lift) : the rocker arm
ratio does not change that and the valve that is opening
13% faster with the 1.65 ratio will end at a maximum
lift that is also 13% higher. </div>
<div>Marcel</div>
<hr id="yiv9741220511zwchr">
<div><b>Van: </b>"Richard Good"
<a href="mailto:goodparts@verizon.net" target="_blank" rel="nofollow noopener noreferrer"><goodparts@verizon.net></a>)<br clear="none">
<b>Aan: </b>"Michael Zbarsky"
<a href="mailto:mzbarsky@yahoo.com" target="_blank" rel="nofollow noopener noreferrer"><mzbarsky@yahoo.com></a>, <a href="mailto:gkbyrne@optusnet.com.au" target="_blank" rel="nofollow noopener noreferrer">gkbyrne@optusnet.com.au</a>,
"van mulders marcel"
<a href="mailto:van.mulders.marcel@telenet.be" target="_blank" rel="nofollow noopener noreferrer"><van.mulders.marcel@telenet.be></a>
<div class="yiv9741220511yqt0090589858" id="yiv9741220511yqtfd74605"><br clear="none">
<b>Cc: </b>"fot" <a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer"><fot@autox.team.net></a><br clear="none">
<b>Verzonden: </b>Woensdag 12 februari 2020 02:23:07<br clear="none">
<b>Onderwerp: </b>Re: [Fot] Camshaft recommendation<br clear="none">
</div>
</div>
<div class="yiv9741220511yqt0090589858" id="yiv9741220511yqtfd30775">
<div> 7.887</div>
<div>
<p dir="ltr">Michael,</p>
<p dir="ltr">People often seem to overlook the main
performance benefit of increasing the rocker ratio.
That is the increase in valve velocity. The
velocity of a flat tappet is limited by it's
diameter. If you grind the cam lobe for too much
velocity the contact patch will move out past the
edge of the lifter and things will self destruct.
So tappet velocity is limited. However, since
tappet velocity times rocker ratio equals valve
velocity, increasing the rocker ratio will increase
valve velocity.</p>
<p dir="ltr">First decide what will be the optimum
valve lift for your engine then divide by rocker
ratio to determine the net cam lift needed to
achieve that valve lift. Yes, you can grind the cam
with a large enough lobe to reach desired lift using
stock rockers but you are limited in how fast you
can open the valve. Now if you grind the cam with
less lift then use 1.65:1 rockers to reach that same
desired valve lift you will be moving the valve
about 13% faster. That means it will be open further
in a given period of time. Graph it out and you
will see a big difference. Valve velocity is a huge
factor in performance. </p>
<p dir="ltr">I can understand why someone who has
tried to use high ratio rockers with a cam that was
already maxing out the valve lift with stock rockers
would decide that high ratio does not work. Valve
lift was already at max. Increasing it further may
be a detriment. If duration was also maxed out for
reasonable torque then the increase in lift during
the overlap period caused by the increase in rocker
ratio may reduce the low end torque. Properly
applied with the right cam profile, high ratio
rockers enable performance that is just not
achievable with stock rockers.</p>
<p dir="ltr">Richard Good<br clear="none">
Good Parts Inc</p>
<p dir="ltr">Sent from AOL Mobile Mail <br clear="none">
Get the new AOL app: mail.mobile.aol.com</p>
<hr style="border:0;min-height:1px;color:#999;background-color:#999;width:100%;margin:0 0 9px 0;padding:0"><span style="font-size:14px;color:#999999">On Tuesday,
February 11, 2020 Michael Zbarsky via Fot <<span style="color:#0000a0"><a href="mailto:mzbarsky@yahoo.com" target="_blank" rel="nofollow noopener noreferrer">mzbarsky@yahoo.com</a></span>>
wrote:</span><br clear="none">
<div>
Thanks everyone! Good stuff. I’m sticking to a
redline of just over 6K. I’d also like to keep the
1.65 setup rather than invest in a 1.55 so keep the
intel and suggestions coming. The GP3 is a definite
contender.
<div><br clear="none">
</div>
<div>Mike <br clear="none">
<br clear="none">
<br clear="none">
<br clear="none">
<div class="yiv9741220511yqt2182859488" id="yiv9741220511yqt21880">
<p class="yiv9741220511yahoo-quoted-begin" style="font-size:15px;color:#715ffa;padding-top:15px;margin-top:0">On
Monday, February 10, 2020, 4:07 PM, Geoff
Byrne <a href="mailto:gkbyrne@optusnet.com.au" target="_blank" rel="nofollow noopener noreferrer"><gkbyrne@optusnet.com.au></a> wrote:</p>
<blockquote class="yiv9741220511iosymail">
<div id="yiv9741220511">
<div>Ditch the 1.65 rockers no good for
racing
<div>Geoff Byrne</div>
<div>TR6 racer down under<br clear="none">
<br clear="none">
<div dir="ltr">Sent from my iPhone</div>
<div dir="ltr"><br clear="none">
<blockquote>On 11 Feb 2020, at 12:52
am, van.mulders.marcel--- via Fot
<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer"><fot@autox.team.net></a> wrote:<br clear="none">
<br clear="none">
</blockquote>
</div>
<blockquote>
<div dir="ltr">
<div style="font-family:'verdana' , 'arial' , 'helvetica' , sans-serif;font-size:10pt;color:#000000">
<div>I also once bought a
Goodparts 1.65 rocker roller
assembly for a TR6 engine, but
in the end I had to use a 1.55
roller rocker assembly, also
from Goodparts, because, with
the 1.65, it is difficult to
find a race camshaft with a
lobe lift that is low enough.
With lobes of 8mm or higher, I
could not find valve springs to
cope with the high valve lift. I
bought a G5 camshaft from
Schneider, they call it the
320-F grind (duration is 268° at
0.050", timing is 57-83 87-53
, installation figure is then
103° :is that the same as the G5
grind?) with 0.340"/8.6mm cam
lift and that makes for a valve
lift of 12.9mm with the 1.55
rocker arms. With 1.65 rockers ,
valve lift would be 14.2mm and I
could not find valve springs for
that lift. The valve springs I
used are part no 281003-063.20
from Summit (Isky), 320lb/inch
spring rate. They recommend
0.45"/11.43mm (1.250" -
0.800"from closed to full open
position, so it is about 1.4mm
more in my engine, but there is
no problem concerning coil
binding : the installed height
is a 1mm more than 1.250 , the
pressure in closed position is
lower of course, but still
34kgs (105kgs at full lift) an
that seems to be enough till
7500 rpm</div>
<div>Racetorations have a race cam
with 7.6mm cam lift, probably
that would work with 1.65 rocker
arms. I still have the 1.65
rocker assembly, it is new and
it could work with a road cam or
any camshaft with a maximum of
8mm cam lift.</div>
<div>Marcel</div>
<div><br clear="none">
</div>
<hr id="yiv9741220511zwchr">
<div><b>Van: </b>"fot"
<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer"><fot@autox.team.net></a><br clear="none">
<b>Aan: </b>"fot"
<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer"><fot@autox.team.net></a><br clear="none">
<b>Verzonden: </b>Maandag 10
februari 2020 02:34:27<br clear="none">
<b>Onderwerp: </b>[Fot]
Camshaft recommendation<br clear="none">
</div>
<div><br clear="none">
</div>
<div>
Hi all, I’m building a TR6 race
engine and have a set of 1.65
ratio roller rockers from
Goodparts. Any recommendations
for a suitable camshaft? I will
be putting in cam bearings.
<div><br clear="none">
<div>Thanks, Mike<br clear="none">
<br clear="none">
<br clear="none">
</div>
</div>
<br clear="none">
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