Andrew---I'll take a stab at this one. I'd first stay around the area of
what changes might have occured as a result of the new parts.
Check to see if an outer valve spring has broken. At low rpm the inner
spring will keep the valve operation working, but this valve can clatter
with increased revs.
Also it is good to have at least .060 of totaled space between the
coils, when the valve is opened.
Engine stethoscopes are cheap and handy for this kind of a hunt.
Dick
From: apackard68@comcast.net(Andrew Packar
d)
Hello list:
It's been a while since I needed serious help figuring out a problem,
but an unfriendly noise developed recently and I fear the worst.
Background:
TR250 with recent engine rebuild. 10:1 compression, GP2 cam, .30
overbore, rimflow valves, uprated valve springs, 1.65 ratio roller
rockers, triple webers, 6-3-1 pulse header, Toyota 5-speed, Nissan
viscous LSD, balanced drive shaft.
Last weekend I adjusted the valve clearances and changed the oil. I had
been about 800-1000 miles since the rebuild, so I removed the regular
oil and replaced it with synthetic, as recommended by the machine shop
that rebuilt the bottom end and did the head work. The valve adjustment
made the engine run smoother as the gaps were high in several of them.
Shortly into my first test drive, I began to hear a sound that sounded
like rocker activity with the valve cover off, but about 2X as loud. I
thought that perhaps a securing nut was loose on one of the rocker arms,
so I readjusted the valves last night, only to hear the same noise while
running. In the garage, the noise is most prevalent at 2000 rpm and
sometimes appears at 1000rpm for a short time. While driving, I can hear
it again at higher rpms on the freeway. With my head under the hood, I
revved the engine enough to create the noise and tried to trace it.
Although it sounded like rocker noise, it seemed to come from the front
of the engine, perhaps at the end of the crankshaft. It's difficult to
pinpoint with the fan spinning and sounds certainly getting deflected
around the engine bay, but that's my best guess and worst fear. The
timing chain was in good shape when I did the engine rebuild, but I did
consider the timing cover as a source of the noise.
Any thoughts are invited and appreciated.
Andy Packard
CD6746L
Bay Area, California
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