BURNT VALVE
Think of it as a home baked pie, now cut and remove a piece using a
spoon. That's what it
looks like. No build up, just a portion melted away.
A lean condition is apt to cause a valve to burn in as much as the
mixture runs "hot", whereas a
richer mixture gives a "quenching" effect, burning somewhat cooler by
comparison. This is not
the only nor most common cause of failure.
The valve not seating properly generally causes a valve to burn. While
the valve is in a
constant state of openness, hot exhaust flows over the thin edges of the
valve face. This causes
hot spots which will eventually, literally, melt.
I am a strong advocate for the use of a good leak down tester
(45-65$'s). With it it is quite easy
to determine whether you problem is a burnt valve, hole in a piston, bad
rings, cracked head or
block, etc.
A quick and easy method to determine a "weak" cylinder is to
(momentarily) remove one spark
plug wire at a time. RPM drop should be about the same between all
cylinders. If one drops
more, you've located the problem cylinder.
WFO Herb
Michael Graziano wrote:
Hey folks.
Didn't have time to recheck that compression last night. In fact,
I'm
pretty busy till next weekend :(. Wedding this weekend :).
BUT, Can you believe, I still have questions!
1: I'm replacing the bushings on the front sway bar and noticed that
the
two locators (stops) had different distances between them and the
bushings.
The passenger side had 1/2 inch and the driver had 7/8". And they
were
positioned between the bushings vs the ouside as in Moss' catalog.
What is
the correct distance, and should they be affixed on the inside,
outside, or
it doesn't matter? And the replacements are the Prothane Poly with
that
lubricant. Does the lubricant go inside the center whole of the
bushing
only, or all around them (inside and between the outside and the
mounts)?
The rubber inside the balls on both links looks pretty dry as well.
Should
I replace those?
2: What do they mean by a "burnt" valve? Are pieces of it melted?
Or is
there simply a layer of caked on goop that interferes with the closing
of
the valve. And why would a lean mixture cause this? How can you tell
if a
valve is burnt without pulling the head?
and 3: The Lower Prothane bushings package reads Midget till '74. I
didn't
think there was a difference from the '74 to the '78. Is there a
compatibility problem? Planning on getting these done next weekend.
Oh so many questions......
Michael
'78 Midget 1500
_____________________________________
/ \
| Michael Graziano |
| Long Term Capital Management L.P. |
| Phone: 203-552-5706 |
| Fax: 203-553-5869 |
| Email: mgrazian@ltcm.com |
\_____________________________________/
|