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Ok, this was our third
time we went into the same chassis dyno in Helsinki and dynoed
10 cars. My Mustang had enjoyed the new GEN2 engine for almost
two months by the time of the dyno, and had seen around 3500
miles. So far I had used two Autolite 2100 1.14 carbs and one
Autolite 2100 1.21, and spent the weeks tuning the car better
and better. I do have a vacuum gauge and a A/F ratio gauge there
and I find them invaluable for the process to tune up a pretty
highly modified power plant like the GEN2 is.
The 1.21 never got into
good tune; it ran lean what ever jets I put in it (tested up
to 68). So the normal thing happened and something totally untested
and unfixed was put into action at the last moment. In a hurry
the day before the dyno I swapped the 1.21 to Holley 350, adjusted
the idle a little and that was it. Dyno day morning I drove to
work using on/off method with the throttle; the 56 jets were
way too small and to avoid total lean outs I had to drive throttle
pedal depressed or pressed enough to open the power valve. Accelerate
- coast - accelerate - coast...
I have basic timing at
28 degrees advanced, vacuum advance not in use, and centrifugals
giving some 17 degrees more at high rpms. For the dyno I filled
the gas tank up with premium pump fuel (98E). Normally I drive
with lower octane stuff (95E).
Anyway, we got to the
event after duty hours at work. The pics continue the saga from
here on... |
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First things first; jet change.
We opened the Holley and decided to change 64 jets in. They were
right on target. Should I leave out the fact that my friend's
jet kit started with 64s... |
Dyno stuff is preparing for the
run. The cars were tied up with strong enough ties and the big
fan (seen left) was placed in front of the cars to provide extra
cooling. |
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We estimated the possibility
to make another run and ended up with changing the 350 out and
a Holley 500 in. Luckily (?) the schedule allowed another pull.
Cranking to get fuel to dry bowl again, fire up, adjust fuel
level, idle mix and speed, and we were readly for the rolls again.
The 500 was equipped with 65 jets, has a thirsty 50cc accelerator
pump and sure is all rock'n'roll, but proved to give no gains
at all to this engine. |
Results:
First run with
Holley 350
112kW / 152hp @ 5200
226Nm @ 3410
Second run
with Holley 500
111kW / 151hp @ 5280
220Nm @ 3470
The std rate valve springs gave
up first, so we never know what the results might have been if
springs would have allowed to measure to at least 5600 rpm (announced
range end of the cam) or to 6000 rpm. Higher rpms might have
given a benefit to the bigger carb but this is all speculation. |
