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Hi,
If your compression and leak down numbers are good, you could have a valve
guide problem. BUT, you should put a vacuum gauge on that engine to see what
sort of vacuum you are pulling. If your ignition timing is way off, it is
possible that the resulting vacuum is the source. Also, you mention "all the
pollution stuff is gone" - that's a red flag to me. The 74 had the following:
crankcase ventilation, e.g. positive crankcase ventilation aka PCV, Exhaust gas
recirculation aka EGR, evaporative emmission control or the carbon canister and
related parts and finally ignition timing retard for idle emissions. Of those,
the only one that would effect performance in any way is the ignition timing
retard.
That said, if you have a high vacuum state and loose valve stems, it is
possible that you are sucking oil down the intake valve guides. If that is the
case, you will see either black or wet plugs or in some cases if you peek into
the spark plug hole you can see carbon deposits on the valve or valves that are
leaking.
IF you can isolate the problem to the valve guides, it is possible to install
valve guide seals without pulling the head. It's not that hard to do. I did
this on a car earlier this year and it solved the problem. I made a tool to
compress the valve spring while I used my leak-down tester to pressurize the
cylinder - you can use the rope trick too - to keep the valve from falling down
into the cylinder.
Regards,Bob Lang
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<html><head></head><body><div class=3D"yahoo-style-wrap" style=3D"font-fami=
ly:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div dir=
=3D"ltr" data-setdir=3D"false">Hi,</div><div dir=3D"ltr" data-setdir=3D"fal=
se"><br></div><div dir=3D"ltr" data-setdir=3D"false"><div>If your compressi=
on and leak down numbers are good, you could have a valve guide problem. BU=
T, you should put a vacuum gauge on that engine to see what sort of vacuum =
you are pulling. If your ignition timing is way off, it is possible that th=
e resulting vacuum is the source. Also, you mention "all the pollution stuf=
f is gone" - that's a red flag to me. The 74 had the following: crankcase v=
entilation, e.g. positive crankcase ventilation aka PCV, Exhaust gas recirc=
ulation aka EGR, evaporative emmission control or the carbon canister and r=
elated parts and finally ignition timing retard for idle emissions. Of thos=
e, the only one that would effect performance in any way is the ignition ti=
ming retard.</div><div><br></div><div dir=3D"ltr" data-setdir=3D"false">Tha=
t said, if you have a high vacuum state and loose valve stems, it is possib=
le that you are sucking oil down the intake valve guides. If that is the ca=
se, you will see either black or wet plugs or in some cases if you peek int=
o the spark plug hole you can see carbon deposits on the valve or valves th=
at are leaking.</div><div dir=3D"ltr" data-setdir=3D"false"><br></div><div =
dir=3D"ltr" data-setdir=3D"false">IF you can isolate the problem to the val=
ve guides, it is possible to install valve guide seals without pulling the =
head. It's not that hard to do. I did this on a car earlier this year and i=
t solved the problem. I made a tool to compress the valve spring while I us=
ed my leak-down tester to pressurize the cylinder - you can use the rope tr=
ick too - to keep the valve from falling down into the cylinder.</div><div =
dir=3D"ltr" data-setdir=3D"false"><br></div><div dir=3D"ltr" data-setdir=3D=
"false">Regards,</div><div dir=3D"ltr" data-setdir=3D"false">Bob Lang<br></=
div><div><div dir=3D"ltr"><br></div></div></div></div></body></html>
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