Just a couple of comments from the lesser of the technos:
Your break occured where most of them break. It might have been cracked for a
very long time. Given the useage of your engine over 21 race weekends
including enduros, not to mention driving the car to the track you did very
well,
methinks.
I ran my old street TR4A engine for several years with no problems in
autocross and other abuses. But when I went to rebuild the engine, the crank
was
'cracked'.
With your self imposed 5500 RPM limit with "VNE" of 6000 RPM, the expense of
a Moldex is not likely justified.
Frankly, I run a crank that is stock (.010) & balanced but nothing else.
Other opinions may prevail, but this is my story, and I am sticking to it.
And I suspect the snout does not have as much to do with the mayhem on your
crankshaft as the flywheel........Investing in a high quality all steel
lightened flywheel might be a suggestion.
Joe (A)
> Group,
>
> I too have just uncovered an arresting discontinuity in my
> crankshaft....number three journal at the aft connection to the
> throw...fairly clean vertical break. The connecting rod was still attached
> to the journal. Nothing came apart.
>
> A Moldex crank might be a little over-kill for a motor which is not revved
> over 5500 rpm, except something went wrong with this last one. It had 21
> races on it including 18 Enduros and another 9500 street miles towing a
> motorcycle trailer.
>
> Which leads me to two questions:
>
> 1. If one "does" a Moldex crank, is one then obliged to then cough up the
> resources for Carrillo rods...and then go for some sort of special pistons?
>
> 2. I have a totally unsupportable notion that my crankshaft failed because
> of fatigue caused by harmonic flex. Several years ago I installed a radiator
> fan and simply unbolted the old iron one. This left that 6" snout wiggling
> out to the front of the engine. Was that a mistake? Should I install an MGB
> harmonic balancer? If I have the crank, flywheel & clutch balanced before
> installation, will this obviate the malevolent harmonic potential?
>
> On the other hand, now that I am down to a raw block, the temptation to
> forget economics and put together a bullet proof bottom end is pretty
> tempting.
>
> I look forward to your comments.
>
> Richard Taylor
> TR-4
> Atlanta
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