Subject: [Fot] GT6 cam timing advice

From: [email-masked]
Date: Mon, 18 Apr 2016 19:45:54 +0000 (UTC)

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FoT=20
I'm building a motor for a club member and am having some difficulty with c=
am timing specs. It's an APT=20
cam and the spec sheet they provided is not only nonsensical but it has som=
e of the data crossed out and=20
some of the numbers hand written in. No real usable data on timing it for i=
t's best performance. At best it's really=20
more of a fast road cam. I didn't spec the cam or buy it. It has 108 degree=
 lobe centers, .280 lobe lift and a=20
duration of 270 degrees at .020 lift. The data sheet says Time to ATDC 103 =
- 104 degrees and it's supposed to have=20
.071 lift at TDC. This cam won't do both.=20
When I time it to 104 degrees ATDC=C2=A0at full lift I get 9 degrees BTDC a=
t .071, which also translates to 20 degrees BTDC at .050 lift=20
which to me sounds more reasonable. I've contacted APT twice now and the fi=
rst answer was a lot of jibberish and they=20
haven't answered the second inquiry yet regarding the math that will not wo=
rk.=20
What I don't want to do is inadvertently RETARD the cam. I'm used to workin=
g with .050 for valve opening but APT doesn't consider=20
.050 an open valve.=20
Any advice would be more than welcome.=20
jim g=20

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<html><body><div style="font-family: Arial; font-size: 12pt; color: #000000"><DIV>FoT<BR></DIV>
<DIV>I'm building a motor for a club member and am having some difficulty with cam timing specs. It's an APT</DIV>
<DIV>cam and the spec sheet they provided is not only nonsensical but it has some of the data crossed out and </DIV>
<DIV>some of the numbers hand written in. No real usable data on timing it for it's best performance. At best it's really </DIV>
<DIV>more of a fast road cam. I didn't spec the cam or buy it. It has 108 degree lobe centers, .280 lobe lift and a </DIV>
<DIV>duration of 270 degrees at .020 lift. The data sheet says Time to ATDC 103 - 104 degrees and it's supposed to have</DIV>
<DIV>.071 lift at TDC. This cam won't do both.</DIV>
<DIV>When I time it to 104 degrees ATDC&nbsp;at full lift I get 9 degrees BTDC at .071, which also translates to 20 degrees BTDC at .050 lift</DIV>
<DIV>which to me sounds more reasonable. I've contacted APT twice now and the first answer was a lot of jibberish and they </DIV>
<DIV>haven't answered the second inquiry yet regarding the math that will not work.</DIV>
<DIV>What I don't want to do is inadvertently RETARD the cam. I'm used to working with .050 for valve opening but APT doesn't consider </DIV>
<DIV>.050 an open valve. </DIV>
<DIV>Any advice would be more than welcome.</DIV>
<DIV>jim g</DIV></div></body></html>
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_______________________________________________
[email-masked]

http://www.fot-racing.com

Archive: http://www.team.net/archive

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From: Rick Parent <[email-masked]>
Date: Tue, 19 Apr 2016 01:52:31 +0000 (UTC)

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Hi Jim,
103-104 at the lobe=C2=A0is where you want to be.=C2=A0The 270 would be at =
the valve.
Hope this helps?
Rick=20

    On Monday, April 18, 2016 6:47 PM, "[email-masked]" <toodamnf=
[email-masked]> wrote:
=20

 FoT
I'm building a motor for a club member and am having some difficulty with c=
am timing specs. It's an APTcam and the spec sheet they provided is not onl=
y nonsensical but it has some of the data crossed out and some of the numbe=
rs hand written in. No real usable data on timing it for it's best performa=
nce. At best it's really more of a fast road cam. I didn't spec the cam or =
buy it. It has 108 degree lobe centers, .280 lobe lift and a duration of 27=
0 degrees at .020 lift. The data sheet says Time to ATDC 103 - 104 degrees =
and it's supposed to have.071 lift at TDC. This cam won't do both.When I ti=
me it to 104 degrees ATDC=C2=A0at full lift I get 9 degrees BTDC at .071, w=
hich also translates to 20 degrees BTDC at .050 liftwhich to me sounds more=
 reasonable. I've contacted APT twice now and the first answer was a lot of=
 jibberish and they haven't answered the second inquiry yet regarding the m=
ath that will not work.What I don't want to do is inadvertently RETARD the =
cam. I'm used to working with .050 for valve opening but APT doesn't consid=
er .050 an open valve. Any advice would be more than welcome.jim g
_______________________________________________
[email-masked]

http://www.fot-racing.com/

tt.net

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<html><head></head><body><div style=3D"color:#000; background-color:#fff; f=
ont-family:HelveticaNeue-Light, Helvetica Neue Light, Helvetica Neue, Helve=
tica, Arial, Lucida Grande, sans-serif;font-size:13px"><div id=3D"yui_3_16_=
0_ym19_1_1461030396303_3488"><span id=3D"yui_3_16_0_ym19_1_1461030396303_34=
87">Hi Jim,</span></div><div><span></span><br></div><div id=3D"yui_3_16_0_y=
m19_1_1461030396303_3499" dir=3D"ltr"><span id=3D"yui_3_16_0_ym19_1_1461030=
396303_3498">103-104 at the lobe&nbsp;is where you want to be.&nbsp;The 270=
 would be at the valve.</span></div><div id=3D"yui_3_16_0_ym19_1_1461030396=
303_3497" dir=3D"ltr"><span></span><br></div><div id=3D"yui_3_16_0_ym19_1_1=
461030396303_3496" dir=3D"ltr"><span>Hope this helps?</span></div><div id=
=3D"yui_3_16_0_ym19_1_1461030396303_3495" dir=3D"ltr"><span></span><br></di=
v><div id=3D"yui_3_16_0_ym19_1_1461030396303_3516" dir=3D"ltr"><span>Rick</=
span></div> <div class=3D"qtdSeparateBR"><br><br></div><div class=3D"yahoo_=
quoted" style=3D"display: block;"> <div style=3D"font-family: HelveticaNeue=
-Light, Helvetica Neue Light, Helvetica Neue, Helvetica, Arial, Lucida Gran=
de, sans-serif; font-size: 13px;"> <div style=3D"font-family: HelveticaNeue=
, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 1=
6px;"> <div dir=3D"ltr"><font face=3D"Arial" size=3D"2"> On Monday, April 1=
8, 2016 6:47 PM, "[email-masked]" &lt;[email-masked]&gt=
; wrote:<br></font></div>  <br><br> <div class=3D"y_msg_container"><div id=
=3D"yiv4681683778"><div><div style=3D"color: rgb(0, 0, 0); font-family: Ari=
al; font-size: 12pt;"><div>FoT<br></div>
<div>I'm building a motor for a club member and am having some difficulty w=
ith cam timing specs. It's an APT</div>
<div>cam and the spec sheet they provided is not only nonsensical but it ha=
s some of the data crossed out and </div>
<div>some of the numbers hand written in. No real usable data on timing it =
for it's best performance. At best it's really </div>
<div>more of a fast road cam. I didn't spec the cam or buy it. It has 108 d=
egree lobe centers, .280 lobe lift and a </div>
<div>duration of 270 degrees at .020 lift. The data sheet says Time to ATDC=
 103 - 104 degrees and it's supposed to have</div>
<div>.071 lift at TDC. This cam won't do both.</div>
<div>When I time it to 104 degrees ATDC&nbsp;at full lift I get 9 degrees B=
TDC at .071, which also translates to 20 degrees BTDC at .050 lift</div>
<div>which to me sounds more reasonable. I've contacted APT twice now and t=
he first answer was a lot of jibberish and they </div>
<div>haven't answered the second inquiry yet regarding the math that will n=
ot work.</div>
<div>What I don't want to do is inadvertently RETARD the cam. I'm used to w=
orking with .050 for valve opening but APT doesn't consider </div>
<div>.050 an open valve. </div>
<div>Any advice would be more than welcome.</div>
<div>jim g</div></div></div></div><br>_____________________________________=
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></div></body></html>
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