[urq] k24 - Schrick combo

[QSHIPQ at aol.com]

Glen:
Advice:  Read Bruce Bell's comments carefully.  I believe if you put pencil 
to paper on the specs of the 272 cam, OR do a back to back comparo of the 272 
cam vs a stock, you just might find that the stock cam outperforms the shrick 
with your combination.

Having done back to back comparos of the 272 to a stock cam (MC big valve 
head, RS2 turbo, 2pc em, ICmod, 3in turbo back) with *all* mods short of 
displacement, I can share that the 272 has too much overlap in the low end to 
justify it's high end goodness.  What rules the world is torque, I think you 
negated your big block gains with a compromised cam choice.  Put another way, 
you can do better than what you have.  

IME, the overlap in the lower rpm band is very noticeable on the 272.  In 
fact, you might see *only* the same boost levels at the same rpm in both (mit 
k24), but the 5psi>5psi comparison is dramatic (btdt).  Back to back tests on 
the 272 (done this swap several times over the years, same day) certainly 
indicates that the lift of the 272 is desireable, but it offsets that with 
duration (=undesireable), and at least IME/O, so much so that the stock cam 
(or the ABT if you can find it) equals or betters performance if you baseline 
them in some measurable way.  Or call Ned, I believe he's got a few good 
choices for you as well (don't forget to ask him about the 272;)

Neither Bruce or I will "argue" that what you have isn't good, but we both 
agree you could have better.  I encourage you to try it out, you just might 
not have to live thru Bruces calculator and spreadsheets (you've been 
warned!:), and my diatribe.

Cheers

Scott Justusson
'87 44tqwRS2 (Abt cam - RS2 turbo)
'84 RS2URQ (RS2cams - RS2 turbo)
'83 Urq (WR cam - k24 turbo)  

In a message dated 3/18/02 12:30:04 AM Central Standard Time, 
bbell at surview.com 
writes:


Hi Glen,

Interesting combination.  Did you start with the k24 then add the cam or
visa versa? You mention, or suggest,  in a subsequent post this is a "full
race engine", I'm wondering if you have any baseline numbers for evaluating
the performance benefit of the changes.  I ask because the combination of
the k24 and Schrick cam are quite a counterintuitive combination to my
thinking. While the K24 is a great turbo for providing low end response and
the Schrick a great cam for high end response, at least in a NA motor, and
this at first blush this would seem reasonable given both cam and turbo are
essentially VE (torque) modifiers and your combination would provide the
best combination to provide torque from low to high. However, the low end
torque provided by the K24 is due in big part to the small exducer on the
turbine. a feature, which at high flow, provides considerable backpressure
in the exhaust manifold and the Schrick 272 (with 50 degrees overlap) does
not want to see high backpressure in the exhaust. In fact too much
backpressure will dramatically reduce VE, especially with lots of overlap.
I'm wondering if you tried other combinations before selecting this one. For
a "full race engine", especially with 2.4 liters and big valves, I would
have expected you to go with the K26 or even the k27 with that cam.

I'd love to see the shape of your torque curve, any chance you have times in
say third gear from 2-3-4-5-6-7 K rpms?

My thinking Glen is that cams, valves and turbos are all VE modifiers but
they can't be considered independently and that the cam and turbo need
consideration as a matched pair for a specific use. i.e. daily driver,
occasional track, race etc.

Without a BTDT on your particular combination, my discourse is purely
philosophical, I'm just hoping you can provide some real world numbers that
the rest of us can use for baseline evaluation.


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