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"it seems most of the better cam grinders these days have some very
fancy software". - That has not been my experience for TR cams, maybe
for SBC cams. - Larry
On 2/22/2020 3:28 AM, Enquiries Road & Track wrote:
> it seems most of the better cam grinders these days have some very
> fancy software for examining the motion of the valve for any cam/valve
> train being proposed. They can easily calculate the critical
> acceleration and deceleration limits for any valve train mass and its
> not hard to 'plot" the motion of the cam/valve lifter, even if they
> did not create the actual cam being studied.  Ive done this on my
> lathe with a data capture system,. Ive just finished a major exercise
> with one cam maker on my Toyota 4AG race engine where I suspected
> valve train harmonics were responsible for a broken cam (actually
> snapped in 2 at peak rpm) . valve spring makers like PAC in the USA
> are known to have such software.
>
> it seems like many TR cam profiles were created in the ancient past,
> possibly more by trial an error than serious maths. Thats not to say
> they are wrong/bad, but rather there is a more modern alternative that
> might have a place. Some cam makers may be using such approaches with
> TR cams, but I suspect many are just churning out what they did 30
> years ago. .
>
> Terry O'Beirne
>
>
> On Sat, Feb 22, 2020 at 2:14 AM Larry Young via Fot
>
> Yes, the down side to a smaller clearance is that the seat-to-seat
> duration and valve overlap will increase causing a loss of the low
> end. This page > http://tildentechnologies.com/Cams/Tip_Lash.html
> shows a case where the duration would increase about 32 degrees to
> about 4x86 = 344 degrees. I like to call this the "tuning fork
> effect" it sets of all kinds of vibrations which can cause the
> valve to jump off the lifter and bounce off the seat at closing.
>
> I did not intend to imply most smack the lifter, just that many
> do. This is a good reason to thoroughly measure your cam profile.
> Most stuff on the web talks about valve springs as the only cure
> for valve float issues.
> Â - Larry
>
> On 2/20/2020 6:51 PM, van.mulders.marcel@telenet.be
>>
>> 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)
>> Marcel
>
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"it seems most of the better cam grinders these days have some very
fancy software". - That has not been my experience for TR cams,
maybe for SBC cams. - Larry<br>
<br>
<div class="moz-cite-prefix">On 2/22/2020 3:28 AM, Enquiries Road
& Track wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CA+UW8b2GeLKbF+ndrY-U0p8Q1pv_LvpP=D-1oG5fuCpmTWL-Lg@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">it seems most of the better cam grinders these days
have some very fancy software for examining the motion of the
valve for any cam/valve train being proposed. They can easily
calculate the critical acceleration and deceleration limits for
any valve train mass and its not hard to 'plot" the motion of
the cam/valve lifter, even if they did not create the actual cam
being studied.  Ive done this on my lathe with a data capture
system,. Ive just finished a major exercise with one cam maker
on my Toyota 4AG race engine where I suspected valve train
harmonics were responsible for a broken cam (actually snapped in
2 at peak rpm) . valve spring makers like PAC in the USA are
known to have such software.
<div><br>
</div>
<div>it seems like many TR cam profiles were created in the
ancient past, possibly more by trial an error than serious
maths. Thats not to say they are wrong/bad, but rather there
is a more modern alternative that might have a place. Some cam
makers may be using such approaches with TR cams, but I
suspect many are just churning out what they did 30 years ago.
.  <br>
<div><br>
</div>
<div>
<div>
<div dir="ltr" data-smartmail="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>Terry O'Beirne</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
</div>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, Feb 22, 2020 at 2:14
AM Larry Young via Fot <<a href="mailto:fot@autox.team.net";
target="_blank" moz-do-not-send="true">fot@autox.team.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF"> Yes, the down side to a smaller
clearance is that the seat-to-seat duration and valve
overlap will increase causing a loss of the low end. This
page > <a
href="http://tildentechnologies.com/Cams/Tip_Lash.html";
target="_blank"
moz-do-not-send="true">http://tildentechnologies.com/Cams/Tip_Lash.html</a>
shows a case where the duration would increase about 32
degrees to about 4x86 = 344 degrees. I like to call this the
"tuning fork effect" it sets of all kinds of vibrations
which can cause the valve to jump off the lifter and bounce
off the seat at closing. <br>
<br>
I did not intend to imply most smack the lifter, just that
many do. This is a good reason to thoroughly measure your
cam profile. Most stuff on the web talks about valve springs
as the only cure for valve float issues.<br>
 - Larry<br>
<br>
<div>On 2/20/2020 6:51 PM, <a
href="mailto:van.mulders.marcel@telenet.be";
target="_blank"
moz-do-not-send="true">van.mulders.marcel@telenet.be</a>
wrote:<br>
</div>
<blockquote type="cite">
<div
style="font-family:Verdana,Arial,Helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)">
<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<br>
</div>
</div>
</blockquote>
<br>
</div>
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