At 09:10 AM 11/27/02 -0700, you wrote:
>That's great documentation Bob! Things like this are as good as gold! ...
>thinking about mildly porting my 4.7L heads now .... Canuck
A little closer examination of the printouts that I got did give
some more valuable information.
I made a pull with a short belt as well since that's the way I run
at the track.
The SAE hp curve (short belt bypassing a/c and ps pullies) showed
240.5 @ 5000 (lowest) to 242.5 @ 5750 with the peak of 243.1 @ 5500.
The SAE torque curve showed 253.9 @ 4000 to 252.6 @5000 (lowest)
with the peak of 259.5 @ 4250. Really flat hp/toque curves around
the peaks and pretty broad. I was expecting recouping a small amount
of hp with the short belt but the torque gain kind of surprised me.
My son took a lot of care with the porting to try and minimize any movement
of the peak torque rpm. We were really surprised that the peak torque
rpm actually went down from that with the stock heads. On the other hand,
the peak hp rpm was a couple hundred rpms above where we had thought that
it would move.
Yesterday's air temp. was near freezing, baro. pressure was an uncharacteristic
30.4" (at least for this area), coolant temp. hovered around 177F and the IAT
sensor showed around 50F during the pulls. This meant that my actual
measured peak hp was about 248 and measured peak torque was about 265.
With my driveline loss, these rw figures translate to an estimated, measured
315 hp and 335 lb-ft at the flywheel. Isn't it fun to play with numbers :-)
My baseline pull was with my ram air box with dual 4" air ducts running
to each side of the rad. I then did the pull above. Then followed that
by changing the air cleaners ... one with none ... one with an open 14 x 2.25
(height of filter restricted by hood clearance of the Gen III).
Being on this side of the border, I couldn't even consider buying the MP RT
heads, let alone the aluminum ones :-)
I've learned another lesson too. Next year, I'll always have a new cap/rotor
with me whenever I go to the track :-)
Bob
This archive was generated by hypermail 2b29 : Fri Feb 06 2004 - 11:47:29 EST