For all you 1/4-milers,
Last winter I ported my heads with the MP porting templates.
My decision for going this route came down to money.
My SAE corrected numbers with the stock heads:
Peak HP: 226.1 @ 5000
Peak Torque: 257.2 @ 4500
My SAE corrected numbers with the ported heads:
Peak HP: 241.7 @ 5750
Peak Torque: 254.1 @ 4250
Unfortunately, circumstances dictated that two dyno shops
using different software and hardware were used so that
comparing the numbers is not exactly like comparing
apples to apples. Also, the printout that I got for the
ported heads were for increments of 250 rpm and not
the normal increments of 100 rpm for the stock heads.
Nevertheless, it gives a close enough ballpark figure of what
to expect.
With my drivetrain loss, there was a gain of about 20 hp at
the flywheel. I certainly was pleasantly surprised to see that
the peak torque rpm had actually dropped a couple of hundreds
of rpms. I also had expected the peak hp rpm to rise but not quite
so high.
As for track performance, weather and track conditions did not
come close to those where I ran my bests last year. 14.313 @ 95.05.
My best this year was 14.42 and I did up my trap speed to 95.92.
At the end of Sept. this year, I began to experience intermittent bucking
and misfiring in the high rpm range. Initial data indicated that the
problem might be air-fuel related and I concentrated on this area.
Last week, I discovered the problem was the cap and rotor. All the
contacts were coated with a hard, thick, 'calcium-like' deposit.
I have never seen a condition like this. Looked like it went through
Jon's mud pit :-)
Also, when the air temps. began hitting the 40Fs and below, I noticed
that my coolant temp. was around 150F (city/highway) and barely cracking
160 at the track. The 180F tstat turned out to be partially stuck open
and I was running quite rich.
Just to show you how much the above problems affect performance, the
dyno numbers with them are:
Peak HP: 217.9 @ 5600
Peak Torque: 245.3 @ 4300
Next week I'll be replacing the RT cam with one that is closer match
to my MPI 4bbl intake and ported heads.
Have a great Thanksgiving, all you USAers.
Bob, Burlington, Ontario.
This archive was generated by hypermail 2b29 : Fri Feb 06 2004 - 11:47:28 EST