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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