WSpohn4@aol.com wrote:
>With a stock cam you can use stock springs. I'm at work and don't have all my
> material here, but I believe the stock valve bounce is about 6200 rpm or so.
> The power peak on a stock engine is well below 6000, but you can run it to
> 6000 all day without needing a cross-drilled crank. 6500 is the frontier
> beyond which stock cranks should not venture!
>
> If you are using a stock gearbox, you will _need_ to use 6000, so that you
> hit somewhere near the torque peak in the next gear.
>
> Bill S.
>
> PS - have fun!
I'm a bit slow following up on this, but I've got some questions.
First, what is "cross-drilling" the crank? How does that help? I assume that
this is a "find a good race prep shop" type thing, and not an off-the-shelf
item, yes? What are the methods and reasons for strenghtening a crank?
Second, about the stock crank: I have a slightly warmed-up cam, stiffer valve
springs, etc. In my last autocross, I touched 6500 at the end of one
particular straight, on each of five runs.
Once, a couple of years ago, the throttle stuck on a shift, and went from 6000
to well past 7000 in the blink of an eye, burying the needle on the tach. I
shut it down ASAP, but still a bit worrysome.
So, I'd say that my motor has spent maybe 15 seconds of its life at 6500+ RPM,
with maybe 5 of those at over 7000. Is the crank just going to snap one of
these days, from the repeated abuse? (Oh, it's a 5-main, from 1970, and it's
ground .020)
Just trying to learn more about the bottom end -- any info. appreciated.
Thanks,
Matt
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