Ron-
Exhaust Valves tend to wear faster because: 1) They get less lubrication
because the pressure from the exhaust gas makes it harder for oil to make
it's way down the valve stem. Since air is being sucked into the engine
during the exhaust stroke, it is easier for oil to make its way down the
valve guide.
2) Exhaust valves are subjected to high temperature exhaust gases. Intake
valves are cooled by the intake charge.
> -----Original Message-----
> From: Ron Soave [SMTP:soavero@yahoo.com]
> Sent: Monday, August 16, 1999 8:38 AM
> To: spridgets@autox.team.net
> Subject: Engine advice needed (kind of long)
>
> Listers,
> You may recall a month ago I posted that my 1275 had
> gone weird driving home from work (car revved like
> crazy, then made no power, gas spitting out carbs,
> etc.). After a month of distractions, I got into it
> the other night and was not too happy with what I
> found. The engine is a 1275 with a road cam, less
> than 2000 miles on it. The engine was broken in
> properly, and the cam was run in properly.
>
> Good news was that the block looked excellent. The
> cylinders were clean as could be, with the honing
> pattern visible perfectly. Bad news is on the #3
> exhaust valve, the adjusting nut on the valve had
> backed completely off the screw. The valve stem was
> beat up pretty badly, with the stem mushroomed beyond
> the diameter of the guide. This I can understand, but
> what really disturbed me was the condition of #1 and
> #2 exhaust valves as well. Both these stems were
> showing signs of wear as well. I assume the exhausts
> wore first because there is more effort for the rocker
> to open them against higher cyclinder pressure? The
> head is off the car right now, but I will check
> pushrod height relative to deck height to see if the
> lifters / cam are ok.
>
> When the engine burped, what happened was the throttle
> cable stuck, and the revs shot up. I believe I caught
> it by 6,000 RPM, but I'm not sure. The engine would
> normally rev to 5500 no problem. I adjusted the
> valves 3 times prior to this incident, and clearances
> were always near correct (.017" for this cam). The
> valves and springs were retained from the original
> engine; guides, seals, rocker assembly are new. Does
> anyone have any ideas, and has anyone seen this
> before? The cam is more radical than stock, but only
> mildly so (similar to a Kent 266). Right now the
> immediate fix is easy and cheap, but I'm afraid this
> is a systemic problem.
>
> Thanks,
> Ron
>
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