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Thanks, Paul!
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.
Thanks!
Stan
On Sun, Jul 14, 2019 at 4:31 AM PaulHunt73 <paulhunt73@virginmedia.com>
wrote:
> IME you should always hear some hissing when putting compressed air into a
> cylinder, ring sealing isn't perfect.
>
> Removing one plug at a time may show which cylinder or cylinders are at
> fault if the pulsing lessens.
>
> Air pulsing out of the rocker cover definitely indicates a major
> compression leak from somewhere, despite your compression readings.
>
> Having said that AFAIK an MGA should also have a 'road draught tube'
> hanging down from the front tappet chest cover, which is another route for
> air to pass in and out of the crankcase. Perhaps that is blocked.
>
> PaulH.
>
> ----- Original Message ----- kcase ventilation
>
> I have an MGA 1600, under 2,000 miles since the engine rebuild. While
> working on an unrelated issue, I discovered that the front air filter was
> thoroughly soaked in oil. The source was the vent hose between the air
> filter and the valve cover. I found significant (to my lack of experience
> with this system!) pulsing air blowing through the hose at idle.
>
>
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Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">Thanks, Paul!<div>I concluded when I cranked the motor wit=
h no plugs installed and still felt the pulsing air that it was not a compr=
ession 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 el=
se would pump air into the crankcase/rocker cover! I checked the draught tu=
be 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 t=
hat with the starter motor turning to see if it's consistent between th=
e two tubes.</div><div>Thanks!</div><div>Stan</div></div><br><div class=3D"=
gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Sun, Jul 14, 2019 at =
4:31 AM PaulHunt73 <<a href=3D"mailto:paulhunt73@virginmedia.com"; target=
=3D"_blank">paulhunt73@virginmedia.com</a>> wrote:<br></div><blockquote =
class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px sol=
id rgb(204,204,204);padding-left:1ex"><u></u>
<div bgcolor=3D"#ffffff">
<div><font size=3D"2">IME you should always hear some hissing when putting=
=20
compressed air into a cylinder, ring sealing isn't perfect.</font></div=
>
<div><font size=3D"2"></font>=C2=A0</div>
<div>
<div><font size=3D"2">Removing one plug at a time may show which cylinder o=
r=20
cylinders are at fault if the pulsing lessens.</font></div>
<div><font size=3D"2"></font>=C2=A0</div></div>
<div><font size=3D"2">Air pulsing out of the rocker cover definitely=C2=A0i=
ndicates=20
a major compression leak from somewhere, despite your compression=20
readings.=C2=A0 </font></div>
<div><font size=3D"2"></font>=C2=A0</div>
<div>
<div><font size=3D"2">Having said that AFAIK an MGA should also have a '=
;road draught=20
tube' hanging down from the front tappet chest cover, which is another =
route for=20
air to pass in and out of the crankcase.=C2=A0 Perhaps that is=20
blocked.</font></div>
<div><font size=3D"2"></font>=C2=A0</div>
<div><font size=3D"2">PaulH.</font></div></div>
<blockquote style=3D"border-left:2px solid rgb(0,0,0);padding-left:5px;padd=
ing-right:0px;margin-left:5px;margin-right:0px">
<div style=3D"font:10pt arial">----- Original Message ----- kcase=20
ventilation</div>
<div><font size=3D"2"></font><br></div>
<div dir=3D"ltr">I have an MGA 1600, under 2,000 miles since the engine r=
ebuild.=20
While working on an unrelated issue, I discovered that the front air filt=
er=20
was thoroughly soaked in oil. The source was the vent hose between the ai=
r=20
filter and the valve cover. I found significant (to my lack of experience=
with=20
this system!) pulsing air blowing through the hose at=20
idle.</div></blockquote></div>
</blockquote></div>
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