On 6/26/11 10:45 PM, Randall wrote:
> However, even the stock camshaft should pull OK out beyond 5000 rpm. The
> factory redline was not because the engine ran out of cam, but because they
> weren't sure it would hold together for the entire warranty period if turned
> faster than that.
Which makes the standard cam good for for a stock engine and maybe a
mild 260 cam might have a bit more pull approaching 5000 RPM. Bigger
cams, like a 280 degree cam pulls strong into the 6000 RPM area but
that is not an area where stock engines should be playing.
if memory serves, the reason for the 5000 RPM red line is that there
is a real nasty harmonic around 5200 - 5400 RPM that breaks the crank at
the base of the flywheel mounting flange if you spend much time in the
low 5000 RPM range.
The whole purpose of the common harmonic dampener kit is to tame that
harmonic.
I don't remember exactly where it is but I believe the next major
harmonic is in the low to mid 6000 RPM range and it tends to break
cranks in the middle and beat up the middle main bearing. Spend much
time in that range and it probably would not hurt to drop the pan and
inspect main bearings every once and a while.
That said, fully prepped race engines often run at 6500 with a nitrided
stock crank.
My TR3 has the harmonic dampener kit and a nitrided crank. I usually
shift at 6000 RPM when I'm on it and the engine has held together well.
I have a 280 degree cam that pulls strongly to about 6000 RPM and has a
wide peak. But with a totally stock engine I would shift at 5000 RPM
just because I worry about major harmonics.
Getting back to cams, compression affects how well they work. If you
have a TR4 head & 87mm pistons the 260 degree cam might be best. But if
you have the TR3 head with less squish area you might see added benefit
with a 280 degree cam and a harmonic dampener kit. You need to go to an
electric pusher fan if you go to the harmonic dampener kit.
There have been soft lifters offered for sale over the years. Either buy
new lifters that have already been individually hardness tested or have
them tested before installing. Each should be Rockwell hardness or 56
or above.
And be sure to use an oil with adequate ZDDP.
Teriann
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