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/*]]>*/</style></div><div>Hallo Chris,</div><div>of course the cylinderhead has to be repaired. I think the man who has put the big valves in it, has taken too much risks : the valve seats (the rings that are pressed into the cyl head) are small where they do meet, and maybe the seats are distorted a bit because of this, but I don't know for sure, I will see when pulling the head. I know one cannot change the valve clearance too much, but maybe 0.05mm more valve lash is ok and it will reduce the valve overlap. I believe 110° overlap is a lot, even for a racecamshaft. Any idea's someone about that? The compression test with increased valve lash is much higher than with the recommended valve lash : I wonder if it is making any sense at all to check the compression of a race engine without increasing the valve lash : with the normal clearances, the inlet valve is closing when the piston has already travelled a lot upwards, hence the big difference between the compression test results with normal and with increased valve lash. So I think, if you want to test the compression, you have to increase the valve lash firstly(at least when the engine has a race camshaft).</div><div>Marcel</div><div><br></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>Zaterdag 2 mei 2020 21:29:59<br><b>Onderwerp: </b>Re: [Fot] Valve overlap and compression test<br></div><div><br></div><div data-marker="__QUOTED_TEXT__"><div class="WordSection1"><p class="MsoNormal"><span lang="DE">Hello Marcel,</span></p><p class="MsoNormal"><span lang="DE"> </span></p><p class="MsoNormal">Your engine has leaking valves.</p><p class="MsoNormal">It won’t get better from changing measurement procedures.</p><p class="MsoNormal">Maybe the seat is rough, or the valves bent, or offset .</p><p class="MsoNormal">Something to make sure about.</p><p class="MsoNormal"> </p><p class="MsoNormal">Enlarging the valve leash could result in hammering everything dead in the valve train.</p><p class="MsoNormal"> </p><p class="MsoNormal">Cheers</p><p class="MsoNormal">Chris</p><p class="MsoNormal"> </p><div><div style="border:none;border-top:solid #e1e1e1 1pt;padding:3pt 0cm 0cm 0cm"><p class="MsoNormal"><b><span lang="DE">Von:</span></b><span lang="DE"> Fot <fot-bounces@autox.team.net> <b>Im Auftrag von </b>van.mulders.marcel--- via Fot<br><b>Gesendet:</b> Samstag, 2. Mai 2020 14:43<br><b>An:</b> fot <fot@autox.team.net><br><b>Betreff:</b> [Fot] Valve overlap and compression test</span></p></div></div><p class="MsoNormal"> </p><div><div><p class="MsoNormal"><span style="font-size:10pt;font-family:'verdana' , sans-serif;color:black">A leaking test on my TR6 engine is showing a leaking exhaust valve on cyl no 1 (48% on the gauge of the device) and a leaking inlet valve on cyl no 2 (75%). Compression on cyl no1 is 9.5 bar and on cyl 2 it is 8 bar. The compression on the other cylinders is between 12 and 13.5 bar. This is with a race cam with a valve overlap of 110° (320-F grind). Because of the high overlap, the piston has risen a lot before the inlet valve is closed, so I did the compression test again, but with a valve lash of 2.5mm/0.1" : compression went from 9.5 bar to 14.5 on cyl no 1 and from 8 bar to 15 on cyl no 2. With this valve lash, the compression on the other cylinders went up to 16 - 18.5 bar. Of course, when the engine is running at high rpm, a lot of valve overlap is necessary for best cylinder filling, but I wonder if 110° isn't too much?? The recommended valve lash is 0.40mm/0.016" when the rocker ratio is 1.45(0.43mm/ with my 1.55 roller rockers). Would it be risky to set the valve lash at some 0.05mm/0.002" higher?</span></p></div><div><p class="MsoNormal"><span style="font-size:10pt;font-family:'verdana' , sans-serif;color:black">PS : is it common practice to set the valve lash at a couple of mm to perform a compression test, because it seems that the valve lash has a lot of influence on the result when testing a race camshaft?</span></p></div><div><p class="MsoNormal"><span style="font-size:10pt;font-family:'verdana' , sans-serif;color:black">Marcel</span></p></div></div></div><br>_______________________________________________<br>fot@autox.team.net<br><br>http://www.fot-racing.com<br><br>Donate: http://www.team.net/donate.html<br>Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot<br>Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/van.mulders.marcel@telenet.be<br></div></div></body></html>