Shane,
I agree with some of your points, but take issue with many more.
First, in your previous post you didn't state that your $100 estimate was
for rear wheel hp, but even so, I think I it is too high.
In your first paragraph, you took my lower figure of 24 hp, not the total hp
of 40 (seen on Kastner's table). What would 40 hp at the crank look like at
the rear wheels.
I agree that I don't have 10:1, but is the difference in .5 compression that
great?
When Kastner says stock in his manual, I take him at his word. If he worked
up the bottom of his motor, it is not stock. Further, my head has been
ported and matched per Vizard's instructions. A bit more than just shaved.
Time will tell if I should have beefed-up the bottom first. Since it is not
a daily driver, I'm betting that I'll not see the need to do this.
Finally, I think the cost per hp is very dependant upon where you start from
and where you end. The cheapest hp gains are at the bottom of the curve and
the most expensive are at the top. I took my engine from stock to a point
part way up the curve. Any gains at this point will cost well in excess of
$100 per hp.
In conclusion, a question. What was the rear wheel hp of a stock 250? Based
upon discussion so far, I'm thinking the 105 number was crank hp.
Peter
'68 TR250 (? hp, maybe I'll get it on a dyno one day)(oh yeah, a blast to
drive)
on 10/5/02 8:16 AM, Shane Ingate at madmax_xx@hotmail.com wrote:
> Peter wrote:
>
>> Anyway, if you look at the power curve in the Kastner manual, this work
>> pushes the hp from stock of 105 to about 139 at 4500RPM an increase of
>> 24hp.
>> If you look at the total hp increase it is more like 40hp. Based upon my
>> costs, this works out to $30 for each horse. Of course, I did the assembly
>> work myself.
>
> Kastener's dyno figures are for *net* horsepower, not at the rear-wheels.
> So his 24hp
> increase at the crank (not even the flywheel) probably equates to 18hp at
> the wheels.
> Further, his curve is for 10:1 compression, not 9.5 as you built into your
> motor.
>
> I am also quite sure that when Kastener did this work, he did not simply
> shave the head
> and throw in a cam; that is not his style as he was a perfectionist. I am
> sure that the
> modified motor was probably balanced, blue-printed, and possibly running
> lightened rods.
> He was probabl also running his lightened pushrods and lifters
> This is worth another 2hp, over the straightforward approach of "bolting on"
> go-faster
> bits.
>
> If we do the sums so far, it is possible that you may have gained 12-14 rwhp
> with the work
> that you performed.
>
> And finally, putting effort into the top-end without rebuilding the bottom
> end is only
> ensuring that you will be rebuilding the bottom-end sooner.
>
> Peter, I am sure that what you did is an absolute blast to drive, and I
> think should
> be a minimum that any owner consider when rebuilding their motor. These
> mods do
> not detract from driveability, makes the motor more responsive and a hoot at
> that.
>
> However, I stand by my statement; horsepower is not cheap. We may argue
> whether
> it costs $80/hp, or $100/hp. I tend to lean towards the higher number,
> because I would
> like to last several seasons between major rebuilds.
>
> Shane Ingate in Maryland
>
>
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