Just got off the chassis dyno with my Morris pickup (948 bored to 972,
Shorrocks supercharger, HIF44 carb), and got it tuned reasonably decently,
but would like to hear some input. At idle, I set it to 15:1 mixture at 8
degree BTDC. I did my initial tests up to 5000 RPM. The BDL needle leans
out too much at the top, but I was able to get top-end performance on a
BBC. BBC was too lean at midrange, so put in a BDK. I hit peak torque at
3200 at 47 ft/lb, and was at 42HP and climbing at 5000 RPM. Torque stays
between 40 and 47 from 2100 to 5000 rpm. Either advancing or retarding the
timing cause slight power loss, so I think I have it dead on.
The remaining problem is that as soon as I hit the throttle, it leans out
to around 18:1 until I hit 2100 RPM, and then starts to richen decently.
This happened on all three needles. My dashpot is full of 20 weight, and I
put in 30 WT and didn't get any significant change. To get it to run well
through that range, I need to richen it to 12:1... fat black smoke at idle.
I can put in either a BDP or a BCA (if I can find one) to get a little
richer on the bottom, but I was wondering if there might be something else
wrong. That leaning with thick dashpot oil has me concerned. Anything else
to look at, or just go ahead with new needles?
KWW
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