<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">I see. Difficult for me to compare, as all of the cam opening/closing data I have is at 50/1000, not the recommended operating clearances. I do agree with Phil Gott’s email that the compression numbers are primarily useful as relative checks against each other. If something is out of line it indicates an issue.<br class=""><div><br class=""><div class="">On May 3, 2020, at 2:25 AM, <a href="mailto:van.mulders.marcel@telenet.be" class="">van.mulders.marcel@telenet.be</a> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class=""><div style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt;" class=""><div class="">Hi Scott,</div><div class="">The 110° degrees is really the valve overlap, in crankshaft degrees, as you understand it, but at the recommended operating valve lash, 0.016". Checking at 0.050" would result in much lower overlap. Installed at 103°(=advanced a bit) , inlet valve is opening 53° before TDC and exhaust valve is closing at 57° after TDC. But 110° is a lot of overlap :the BFE24 grind has 112° but most racecams are between 95 and 105° it seems. The cam in my engine is installed at 104°, I'm thinking of trying to advance it to 100° ; then the inlet valve is closing earlier. Now the engine has a REAL 210 hp, with the leaking valves and I'm just starting the testing on my engine dyno. People who are racing TR6 engines are easily talking about 230 and 250hp but you never know what that means. But 210° is disappointing, it should go up, more so because the displacement is 2720cc (evenly spaced bores of 78mm)</div><div class="">Marcel</div><div class=""><br class=""></div><hr id="zwchr" data-marker="__DIVIDER__" class=""><div data-marker="__HEADERS__" class=""><b class="">Van: </b>"Scott Janzen" <<a href="mailto:sjanzen@me.com" class="">sjanzen@me.com</a>><br class=""><b class="">Aan: </b>"van mulders marcel" <<a href="mailto:van.mulders.marcel@telenet.be" class="">van.mulders.marcel@telenet.be</a>><br class=""><b class="">Cc: </b>"tr4racing" <<a href="mailto:tr4racing@googlemail.com" class="">tr4racing@googlemail.com</a>>, "fot" <<a href="mailto:fot@autox.team.net" class="">fot@autox.team.net</a>><br class=""><b class="">Verzonden: </b>Zaterdag 2 mei 2020 23:36:31<br class=""><b class="">Onderwerp: </b>Re: [Fot] Valve overlap and compression test<br class=""></div><div class=""><br class=""></div><div data-marker="__QUOTED_TEXT__" class="">Maercel, I’m puzzled. Are you referring to the lobe separation angle, or to the overlap between the intake valve opening before TDC and the exhaust valve closing after TDC on the same revolution? Unless I’m reading them wrong, I’ve looked at some pretty radical cam specs and the opening/closing overlap does not approach 110 degrees, more like 50 degrees on a really aggressive cam, but the lobe separation angle is about 104 degrees on the cam I have in the car and 107 on the cam I’m putting in another engine.<br class=""><div class=""><br class=""><div class="">On May 2, 2020, at 4:30 PM, van.mulders.marcel--- via Fot <<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer" class="">fot@autox.team.net</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-style:normal;font-weight:normal;letter-spacing:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;font-family:'verdana' , 'arial' , 'helvetica' , sans-serif;font-size:10pt" class=""><div class=""></div><div class="">Hallo Chris,</div><div class="">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 class="">Marcel</div><div class=""><br class=""></div><hr id="zwchr" class=""><div class=""><b class="">Van:<span class="Apple-converted-space"> </span></b>"fot" <<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer" class="">fot@autox.team.net</a>><br class=""><b class="">Aan:<span class="Apple-converted-space"> </span></b>"fot" <<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer" class="">fot@autox.team.net</a>><br class=""><b class="">Verzonden:<span class="Apple-converted-space"> </span></b>Zaterdag 2 mei 2020 21:29:59<br class=""><b class="">Onderwerp:<span class="Apple-converted-space"> </span></b>Re: [Fot] Valve overlap and compression test<br class=""></div><div class=""><br class=""></div><div class=""><div class="WordSection1"><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class=""><span lang="DE" class="">Hello Marcel,</span></div><p class="MsoNormal" style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif"><span lang="DE" class=""> </span></p><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">Your engine has leaking valves.</div><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">It won’t get better from changing measurement procedures.</div><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">Maybe the seat is rough, or the valves bent, or offset .</div><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">Something to make sure about.</div><p class="MsoNormal" style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif"> </p><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">Enlarging the valve leash could result in hammering everything dead in the valve train.</div><p class="MsoNormal" style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif"> </p><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">Cheers</div><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class="">Chris</div><p class="MsoNormal" style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif"> </p><div class=""><div style="border-style:solid none none;border-top-width:1pt;border-top-color:rgb( 225 , 225 , 225 );padding:3pt 0cm 0cm" class=""><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class=""><b class=""><span lang="DE" class="">Von:</span></b><span lang="DE" class=""><span class="Apple-converted-space"> </span>Fot <<a href="mailto:fot-bounces@autox.team.net" target="_blank" rel="nofollow noopener noreferrer" class="">fot-bounces@autox.team.net</a>><span class="Apple-converted-space"> </span><b class="">Im Auftrag von<span class="Apple-converted-space"> </span></b>van.mulders.marcel--- via Fot<br class=""><b class="">Gesendet:</b><span class="Apple-converted-space"> </span>Samstag, 2. Mai 2020 14:43<br class=""><b class="">An:</b><span class="Apple-converted-space"> </span>fot <<a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer" class="">fot@autox.team.net</a>><br class=""><b class="">Betreff:</b><span class="Apple-converted-space"> </span>[Fot] Valve overlap and compression test</span></div></div></div><p class="MsoNormal" style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif"> </p><div class=""><div class=""><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class=""><span style="font-size:10pt;font-family:'verdana' , sans-serif" class="">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></div></div><div class=""><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class=""><span style="font-size:10pt;font-family:'verdana' , sans-serif" class="">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></div></div><div class=""><div style="margin:0cm;font-size:11pt;font-family:'calibri' , sans-serif" class=""><span style="font-size:10pt;font-family:'verdana' , sans-serif" class="">Marcel</span></div></div></div></div><br class="">_______________________________________________<br class=""><a href="mailto:fot@autox.team.net" target="_blank" rel="nofollow noopener noreferrer" class="">fot@autox.team.net</a><br class=""><br class=""><a href="http://www.fot-racing.com/" target="_blank" rel="nofollow noopener noreferrer" 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