> Hello, new to the list here...I was wondering if anyone had a ballpark
> figure
> as to how high the TR4 engine can be revved with stock but prepared
> crank and
> rods (nitrided, shot peened, balanced)? Will they hold up to an
> occasional
> 6,000 RPMs? How about 6,500? Or would that be risking a blow-up...
As one who drives a TR3A who's tack needle frequently visits the 6000
RPM line I would be happy to tackle that question:
There are major crank shaft harmonics around 5200, 5800 and 6200 RPM.
The one at 5200 RPM tends to break the crank at the base of the
flywheel mounting flange if you spend much time there. The one at 6200
is at the middle of the crank and tends to beat up the middle main
bearing. Time may tell me what the 5800 RPM harmonic breaks.
Triumph factory race cars were red lined at 5000 RPM (same as a stock
engine) so they would not break the crank on a long race.
There is a harmonic dampener kit currently available (Racetorations in
the UK, British Frame & Engine in the US) that tames the 5200 RPM
harmonic quite a bit and possibly the others as well. Nitriding the
crank increases its hardness and is a must if you want to rev the
engine. So are such things as balancing the engine, lightening the
rocker assembly, going to an aluminium flywheel and going to stronger
valve springs and retainers.
Also be aware that current stock non asbestos clutch disk linings seem
to come apart if you spend much time at or above 6000 RPM.
Revs above 5000 are not for the stock engine without a shelf of spare
cranks. if you want to spend time above 6000 RPMs you would have to
get serious about special cranks and rods. Nitriding & balancing will
not be enough.
TeriAnn J. Wakeman
Marigold Ltd.
www.marigoldltd.com
/// triumphs@autox.team.net mailing list
/// or try http://www.team.net/cgi-bin/majorcool
/// Archives at http://www.team.net/archive
|