<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Isn't part of the reason that the valve 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="AppleMailSignature">Maybe try a 4 thou valve clearance and see how it goes? </div><div id="AppleMailSignature">I probably won't!! </div><div id="AppleMailSignature">:-)</div><div id="AppleMailSignature">Chris <br><br>Sent from my iPhone</div><div><br>On 14 Jan 2019, at 10:23 am, Michael Salter <<a href="mailto:michael.salter@gmail.com">michael.salter@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="auto">This is another subject that I often wonder about. <div dir="auto">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 engine after a dyno run, are they hardly any less than they were cold?</div><div dir="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="auto">I also appreciate that the exhaust valve stem get really hot but ????</div><div dir="auto">Just wondering....</div><div dir="auto"><br></div><div dir="auto">M</div></div><br><div class="gmail_quote"><div dir="ltr">On Sun, Jan 13, 2019, 6:42 AM WILLIAM B LAWRENCE <<a href="mailto:ynotink@msn.com">ynotink@msn.com</a> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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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 valve clearances are calculated
to assure that this expansion isn't allowed to 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. Also i<span style="font-family:Calibri,Helvetica,sans-serif;background-color:rgb(255,255,255);display:inline!important">ncreasing the duration and/or lift of the cam has the effect of the decreasing 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. Increasing the valve clearance restores the dwell time the valve needs to transfer its heat load to the cooling system through
the valve seat and the cylinder head. Too little dwell time or the lack of proper valve sealing are two causes of burned valves.</span></div>
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In my own experience I installed an Isky cam with a grind a little more aggressive 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 time to read the Isky installation
instructions which specifically state the valve clearance needs to be set to 0.018". I re-installed the head with new valves and set them to Isky's spec and never had another problem with burned valves.</div>
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Follow the cam grinder's recommendations and you will avoid trouble.</div>
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Bill Lawrence</div>
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BN1 #554</div>
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<div id="m_1603937236670712738divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Healeys <<a href="mailto:healeys-bounces@autox.team.net" target="_blank" rel="noreferrer">healeys-bounces@autox.team.net</a>> on behalf of Bob Spidell <<a href="mailto:bspidell@comcast.net" target="_blank" rel="noreferrer">bspidell@comcast.net</a>><br>
<b>Sent:</b> Saturday, January 12, 2019 11:10 PM<br>
<b>To:</b> Michael MacLean; <a href="mailto:healeys@autox.team.net" target="_blank" rel="noreferrer">healeys@autox.team.net</a><br>
<b>Subject:</b> Re: [Healeys] Valve clearances</font>
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<p>I should note the rockers are pretty noisy at 0.015; IIRC I tightened them up just a bit.<br>
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<div class="m_1603937236670712738x_moz-cite-prefix">On 1/12/2019 2:39 PM, Michael MacLean wrote:<br>
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<div>I'd go with .016. You can always tighten it. Better loose than tight.</div>
<div>Mike MacLean<br>
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<div>On Saturday, January 12, 2019, 11:01:32 AM PST, Bob Spidell <a class="m_1603937236670712738x_moz-txt-link-rfc2396E" href="mailto:bspidell@comcast.net" target="_blank" rel="noreferrer">
<bspidell@comcast.net></a> wrote: </div>
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<p>Makes sense (for some reason). I put a DWR1 cam in my BJ8 which, according to DWR, 'is a little better than the BJ8 cam and so works well in any standard or mildly tuned car' but I think the 0.015" applies to all profiles on the spec sheet.<br clear="none">
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<p>Bob<br clear="none">
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<div class="m_1603937236670712738x_yiv1110160614moz-cite-prefix">On 1/11/2019 8:48 PM, John Rowe wrote:<br clear="none">
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<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span style="color:#1f497d">Simon,</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span style="color:#1f497d">Modified cams require the large clearance (don’t ask me why?) So go for .015 that is what mine is.</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span style="color:#1f497d">John Rowe</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span style="color:#1f497d">Qld</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span style="color:#1f497d">Australia</span></p>
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<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt">From:</span></b><span lang="EN-US" style="font-size:10.0pt"> Healeys [<a rel="nofollow noreferrer" shape="rect" class="m_1603937236670712738x_yiv1110160614moz-txt-link-freetext" href="mailto:healeys-bounces@autox.team.net" target="_blank">mailto:healeys-bounces@autox.team.net</a>]
<b>On Behalf Of </b><a rel="nofollow noreferrer" shape="rect" class="m_1603937236670712738x_yiv1110160614moz-txt-link-abbreviated" href="mailto:simon.lachlan@alexarevel.plus.com" target="_blank">simon.lachlan@alexarevel.plus.com</a><br clear="none">
<b>Sent:</b> Saturday, 12 January 2019 9:14 AM<br clear="none">
<b>To:</b> Healeys<br clear="none">
<b>Subject:</b> [Healeys] Valve clearances</span></p>
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<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">The car is a MkII BT7.</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">The BMC manual says adjust the clearances, cold, to 0.012”.</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">Denis Welch said I should go 0.015”, cold, after fitting their “Fast Road” cam.</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">The rolling road guy said 0.016”, warm.</span></p>
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<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">I have the radiator out right now so I can get a nice socket onto that nut and have a go at the clearances.</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">Stick with 0.015”, cold?</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB"> </span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">Thanks,</span></p>
<p class="m_1603937236670712738x_yiv1110160614MsoNormal"><span lang="EN-GB">Simon</span></p>
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