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Isn't part of the reason that the valve dissipates heat into the head when i=
t is seated, so part of the reason for valve clearance is to allow the valve=
to cool?
Maybe try a 4 thou valve clearance and see how it goes?=20
I probably won't!!=20
:-)
Chris=20
Sent from my iPhone
> On 14 Jan 2019, at 10:23 am, Michael Salter <michael.salter@gmail.com> wro=
te:
>=20
> This is another subject that I often wonder about.=20
> If the valve clearance is there to ensure that the valves are fully closed=
when the engine is hot then why, when I check the clearances on a hot engin=
e after a dyno run, are they hardly any less than they were cold?
> I can appreciate that the valve train components grow because of the heat b=
ut surely the block and head and rocker shaft pedistals also grow and thus t=
here is little if any net change.
> I also appreciate that the exhaust valve stem get really hot but ????
> Just wondering....
>=20
> M
>=20
>> On Sun, Jan 13, 2019, 6:42 AM WILLIAM B LAWRENCE <ynotink@msn.com wrote:
>> I disagree that valve clearances are not critical. As the engine comes up=
to temperature the metal parts of the valve train (valves, lifters, push ro=
ds, the head itself and the rocker shaft towers) increase in length and the v=
alve clearances are calculated to assure that this expansion isn't allowed t=
o affect the sealing of the valves on their seats. If the valves are set too=
tight they reach a point where they won't touch the seats and therefore won=
't seal. Hot gases rushing through the gaps will quickly erode the valves. A=
lso increasing the duration and/or lift of the cam has the effect of the de=
creasing the length of the opening and closing ramps on the back side of the=
cam This reduces the length of time (dwell) the valve remains on the seat. I=
ncreasing the valve clearance restores the dwell time the valve needs to tra=
nsfer its heat load to the cooling system through the valve seat and the cyl=
inder head. Too little dwell time or the lack of proper valve sealing are tw=
o causes of burned valves.
>>=20
>> In my own experience I installed an Isky cam with a grind a little more a=
ggressive than the 100M cam and set the clearances to 0.012" per the manual.=
Within about 2,000 miles the exhaust valves were trashed. I then took the t=
ime to read the Isky installation instructions which specifically state the v=
alve clearance needs to be set to 0.018". I re-installed the head with new v=
alves and set them to Isky's spec and never had another problem with burned v=
alves.
>>=20
>> Follow the cam grinder's recommendations and you will avoid trouble.
>>=20
>> Bill Lawrence
>> BN1 #554
>> From: Healeys <healeys-bounces@autox.team.net> on behalf of Bob Spidell <=
bspidell@comcast.net>
>> Sent: Saturday, January 12, 2019 11:10 PM
>> To: Michael MacLean; healeys@autox.team.net
>> Subject: Re: [Healeys] Valve clearances
>> =20
>> I should note the rockers are pretty noisy at 0.015; IIRC I tightened the=
m up just a bit.
>>> On 1/12/2019 2:39 PM, Michael MacLean wrote:
>>> I'd go with .016. You can always tighten it. Better loose than tight.
>>> Mike MacLean
>>>=20
>>> On Saturday, January 12, 2019, 11:01:32 AM PST, Bob Spidell <bspidell@co=
mcast.net> wrote:
>>>=20
>>>=20
>>> Makes sense (for some reason). I put a DWR1 cam in my BJ8 which, accord=
ing to DWR, 'is a little better than the BJ8 cam and so works well in any st=
andard or mildly tuned car' but I think the 0.015" applies to all profiles o=
n the spec sheet.
>>> Bob
>>>> On 1/11/2019 8:48 PM, John Rowe wrote:
>>>=20
>>> Simon,
>>>=20
>>> Modified cams require the large clearance (don=E2=80=99t ask me why?) So=
go for .015 that is what mine is.
>>>=20
>>> John Rowe
>>>=20
>>> Qld
>>>=20
>>> Australia
>>>=20
>>> =20
>>>=20
>>> From: Healeys [mailto:healeys-bounces@autox.team.net] On Behalf Of simon=
.lachlan@alexarevel.plus.com
>>> Sent: Saturday, 12 January 2019 9:14 AM
>>> To: Healeys
>>> Subject: [Healeys] Valve clearances
>>>=20
>>> =20
>>>=20
>>> The car is a MkII BT7.
>>>=20
>>> The BMC manual says adjust the clearances, cold, to 0.012=E2=80=9D.
>>>=20
>>> Denis Welch said I should go 0.015=E2=80=9D, cold, after fitting their =E2=
=80=9CFast Road=E2=80=9D cam.
>>>=20
>>> The rolling road guy said 0.016=E2=80=9D, warm.
>>>=20
>>> =20
>>>=20
>>> I have the radiator out right now so I can get a nice socket onto that n=
ut and have a go at the clearances.
>>>=20
>>> Stick with 0.015=E2=80=9D, cold?
>>>=20
>>> =20
>>>=20
>>> Thanks,
>>>=20
>>> Simon
>>>=20
>>>=20
>>>=20
>>>=20
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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div>Isn't part of the reason that the valv=
e dissipates heat into the head when it is seated, so part of the reason for=
valve clearance is to allow the valve to cool?</div><div id=3D"AppleMailSig=
nature">Maybe try a 4 thou valve clearance and see how it goes? </div><=
div id=3D"AppleMailSignature">I probably won't!! </div><div id=3D"Apple=
MailSignature">:-)</div><div id=3D"AppleMailSignature">Chris <br><br>Se=
nt from my iPhone</div><div><br>On 14 Jan 2019, at 10:23 am, Michael Salter &=
lt;<a href=3D"mailto:michael.salter@gmail.com";>michael.salter@gmail.com</a>&=
gt; wrote:<br><br></div><blockquote type=3D"cite"><div><div dir=3D"auto">Thi=
s is another subject that I often wonder about. <div dir=3D"auto">If th=
e valve clearance is there to ensure that the valves are fully closed when t=
he engine is hot then why, when I check the clearances on a hot engine after=
a dyno run, are they hardly any less than they were cold?</div><div d=
ir=3D"auto">I can appreciate that the valve train components grow because of=
the heat but surely the block and head and rocker shaft pedistals also grow=
and thus there is little if any net change.</div><div dir=3D"auto">I also a=
ppreciate that the exhaust valve stem get really hot but ????</div><div dir=3D=
"auto">Just wondering....</div><div dir=3D"auto"><br></div><div dir=3D"auto"=
>M</div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr">On Sun, Jan 13=
, 2019, 6:42 AM WILLIAM B LAWRENCE <<a href=3D"mailto:ynotink@msn.com";>yn=
otink@msn.com</a> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D=
"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir=3D"ltr">
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
I disagree that valve clearances are not critical. As the engine comes up to=
temperature the metal parts of the valve train (valves, lifters, push rods,=
the head itself and the rocker shaft towers) increase in length and the val=
ve clearances are calculated
to assure that this expansion isn't allowed to affect the sealing of the va=
lves on their seats. If the valves are set too tight they reach a point wher=
e they won't touch the seats and therefore won't seal. Hot gases rushing thr=
ough the gaps will quickly erode
the valves. Also i<span style=3D"font-family:Calibri,Helvetica,sans-serif;b=
ackground-color:rgb(255,255,255);display:inline!important">ncreasing the dur=
ation and/or lift of the cam has the effect of the decreasing the leng=
th
of the opening and closing ramps on the back side of the cam This reduces t=
he length of time (dwell) the valve remains on the seat. Increasing the valv=
e clearance restores the dwell time the valve needs to transfer its heat loa=
d to the cooling system through
the valve seat and the cylinder head. Too little dwell time or the lack of p=
roper valve sealing are two causes of burned valves.</span></div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
<br>
</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
In my own experience I installed an Isky cam with a grind a little more aggr=
essive than the 100M cam and set the clearances to 0.012" per the manual. Wi=
thin about 2,000 miles the exhaust valves were trashed. I then took the time=
to read the Isky installation
instructions which specifically state the valve clearance needs to be set t=
o 0.018". I re-installed the head with new valves and set them to Isky's spe=
c and never had another problem with burned valves.</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
<br>
</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
Follow the cam grinder's recommendations and you will avoid trouble.</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
<br>
</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
Bill Lawrence</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt;color:=
rgb(0,0,0)">
BN1 #554</div>
<div id=3D"m_1603937236670712738appendonsend"></div>
<hr style=3D"display:inline-block;width:98%">
<div id=3D"m_1603937236670712738divRplyFwdMsg" dir=3D"ltr"><font face=3D"Cal=
ibri, sans-serif" style=3D"font-size:11pt" color=3D"#000000"><b>From:</b> He=
aleys <<a href=3D"mailto:healeys-bounces@autox.team.net"; target=3D"_blank=
" rel=3D"noreferrer">healeys-bounces@autox.team.net</a>> on behalf of Bob=
Spidell <<a href=3D"mailto:bspidell@comcast.net"; target=3D"_blank" rel=3D=
"noreferrer">bspidell@comcast.net</a>><br>
<b>Sent:</b> Saturday, January 12, 2019 11:10 PM<br>
<b>To:</b> Michael MacLean; <a href=3D"mailto:healeys@autox.team.net"; target=
=3D"_blank" rel=3D"noreferrer">healeys@autox.team.net</a><br>
<b>Subject:</b> Re: [Healeys] Valve clearances</font>
<div> </div>
</div>
<div style=3D"background-color:#ffffff">
<p>I should note the rockers are pretty noisy at 0.015; IIRC I tightened the=
m up just a bit.<br>
</p>
<div class=3D"m_1603937236670712738x_moz-cite-prefix">On 1/12/2019 2:39 PM, M=
ichael MacLean wrote:<br>
</div>
<blockquote type=3D"cite">
<div class=3D"m_1603937236670712738x_ydpe1d3e9c5yahoo-style-wrap" style=3D"f=
ont-family:times new roman,new york,times,serif;font-size:16px">
<div>I'd go with .016. You can always tighten it. Better loose t=
han tight.</div>
<div>Mike MacLean<br>
</div>
<div><br>
</div>
</div>
<div id=3D"m_1603937236670712738x_yahoo_quoted_8268064185" class=3D"m_160393=
7236670712738x_yahoo_quoted">
<div style=3D"font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;font-s=
ize:13px;color:#26282a">
<div>On Saturday, January 12, 2019, 11:01:32 AM PST, Bob Spidell <a class=3D=
"m_1603937236670712738x_moz-txt-link-rfc2396E" href=3D"mailto:bspidell@comca=
st.net" target=3D"_blank" rel=3D"noreferrer">
<bspidell@comcast.net></a> wrote: </div>
<div><br>
</div>
<div><br>
</div>
<div>
<div id=3D"m_1603937236670712738x_yiv1110160614">
<div>
<p>Makes sense (for some reason). I put a DWR1 cam in my BJ8 which, ac=
cording to DWR, 'is a little better than the BJ8 cam and so works well in an=
y standard or mildly tuned car' but I think the 0.015" applies to all profil=
es on the spec sheet.<br clear=3D"none">
</p>
<p>Bob<br clear=3D"none">
</p>
<div class=3D"m_1603937236670712738x_yiv1110160614yqt0287165987" id=3D"m_160=
3937236670712738x_yiv1110160614yqt70378">
<div class=3D"m_1603937236670712738x_yiv1110160614moz-cite-prefix">On 1/11/2=
019 8:48 PM, John Rowe wrote:<br clear=3D"none">
</div>
<blockquote type=3D"cite"></blockquote>
</div>
</div>
<div class=3D"m_1603937236670712738x_yiv1110160614yqt0287165987" id=3D"m_160=
3937236670712738x_yiv1110160614yqt92654">
<div>
<div class=3D"m_1603937236670712738x_yiv1110160614WordSection1">
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span style=3D"co=
lor:#1f497d">Simon,</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span style=3D"co=
lor:#1f497d">Modified cams require the large clearance (don=E2=80=99t ask me=
why?) So go for .015 that is what mine is.</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span style=3D"co=
lor:#1f497d">John Rowe</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span style=3D"co=
lor:#1f497d">Qld</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span style=3D"co=
lor:#1f497d">Australia</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span style=3D"co=
lor:#1f497d"> </span></p>
<div>
<div style=3D"border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0=
cm 0cm">
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><b><span lang=3D"=
EN-US" style=3D"font-size:10.0pt">From:</span></b><span lang=3D"EN-US" style=
=3D"font-size:10.0pt"> Healeys [<a rel=3D"nofollow noreferrer" shape=3D"rect=
" class=3D"m_1603937236670712738x_yiv1110160614moz-txt-link-freetext" href=3D=
"mailto:healeys-bounces@autox.team.net"; target=3D"_blank">mailto:healeys-bou=
nces@autox.team.net</a>]
<b>On Behalf Of </b><a rel=3D"nofollow noreferrer" shape=3D"rect" class=3D"m=
_1603937236670712738x_yiv1110160614moz-txt-link-abbreviated" href=3D"mailto:=
simon.lachlan@alexarevel.plus.com" target=3D"_blank">simon.lachlan@alexareve=
l.plus.com</a><br clear=3D"none">
<b>Sent:</b> Saturday, 12 January 2019 9:14 AM<br clear=3D"none">
<b>To:</b> Healeys<br clear=3D"none">
<b>Subject:</b> [Healeys] Valve clearances</span></p>
</div>
</div>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"> </p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">The car is a MkII BT7.</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">The BMC manual says adjust the clearances, cold, to 0.012=E2=80=9D.</spa=
n></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">Denis Welch said I should go 0.015=E2=80=9D, cold, after fitting their =E2=
=80=9CFast Road=E2=80=9D cam.</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">The rolling road guy said 0.016=E2=80=9D, warm.</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB"> </span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">I have the radiator out right now so I can get a nice socket onto that n=
ut and have a go at the clearances.</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">Stick with 0.015=E2=80=9D, cold?</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB"> </span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">Thanks,</span></p>
<p class=3D"m_1603937236670712738x_yiv1110160614MsoNormal"><span lang=3D"EN-=
GB">Simon</span></p>
</div>
<br>
</div>
</div>
</div>
</div>
</div>
</div>
<div id=3D"m_1603937236670712738x_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2">
<table style=3D"border-top:1px solid #d3d4de">
<tbody>
<tr>
<td style=3D"width:55px;padding-top:13px"><br>
</td>
<td style=3D"width:470px;padding-top:12px;color:#41424e;font-size:13px;font-=
family:Arial,Helvetica,sans-serif;line-height:18px"><br></td></tr></tbody></=
table></div></blockquote></div></div></blockquote></div></div></blockquote><=
/body></html>=
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