<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=utf-8" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 8.00.6001.23588">
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT size=2>If it's not compression leaking then I can't think what would
cause excessive pulsing out of the breathers. Except ...</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Although two pistons are going down while the other two
are going up, the movement is not symmetrical. Don't ask me to explain the
physical logic behind it, but when the crank has turned 90
degrees </FONT><FONT size=2>from TDC the piston has moved more than halfway
down the stroke, and from that position to BDC the piston moves less
than half the stroke. So for that 90 degrees of crank movement the
undersides of the pistons coming down the first 'half' of the
stroke are displacing more air than the ones going up can
'absorb' so you get a positive pressure, but for the second half of the strokes
the situation is reversed to give a slight negative pressure. But on my
MGB - different crankcase ventilation system but still two routes in and out of
the crankcase - I can seal off one and I get no more than a slight fluttering in
the other.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Maybe the problem is not so much excessive pulsing, with you
expecting there to be no movement in the breather at all, but excessive oil in
the rocker cover around the vent. The road-draught system is
pretty hit and miss as to which way air will flow through the crankcase,
and I wouldn't have though that suck unfiltered air in from the road-draught
tube was a Good Thing, but if the intake can suck air through the rocker cover
tube at any time, then it will draw oil along with it. The question is why
there should be enough negative pressure on that tube to do it. I don't
know about the MGA but on the MGB that tube is on the 'dirty' side of the
filter, which in theory shouldn't be under significant negative pressure, unlike
the 'clean' side of the filter at wide throttle openings. Unless the
intake to the can is restricted somehow. But if the tube is connected to
the clean side of the filter then the intake system will be continually sucking
air through the tube, and any oil droplets that are in the
vicinity.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>PaulH.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"
dir=ltr>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=spridget@gmail.com href="mailto:spridget@gmail.com">Stan Fickes</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=paulhunt73@virginmedia.com
href="mailto:paulhunt73@virginmedia.com">PaulHunt73</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=mgs@autox.team.net
href="mailto:mgs@autox.team.net">mgs@autox.team.net</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, July 14, 2019 8:05 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Mgs] MGA crankcase
ventilation</DIV>
<DIV><BR></DIV>
<DIV dir=ltr>Thanks, Paul!
<DIV>I concluded when I cranked the motor with no plugs installed and still
felt the pulsing air that it was not a compression issue. For completeness, I
need to try the same thing with the plugs installed, to see if there is a
difference. I just can't think what else would pump air into the
crankcase/rocker cover! I checked the draught tube this afternoon by squirting
some low-pressure air into the rocker cover tube, and felt a gentle stream of
air out the bottom. I should also check that with the starter motor turning to
see if it's consistent between the two tubes.</DIV>
<DIV>Thanks!</DIV>
<DIV>Stan</DIV></DIV>
<DIV class=gmail_quote>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>
<DIV bgcolor="#ffffff">
<BLOCKQUOTE
style="BORDER-LEFT: rgb(0,0,0) 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV
dir=ltr> </DIV></BLOCKQUOTE></DIV></BLOCKQUOTE></DIV></BLOCKQUOTE></BODY></HTML>