[chiphead]

I'm mainly concerned with near WOT curve for now. Steady road cruise is fairly close. I get 18" at light throttle on a flat road at 2400.

Basically, could I add 2* of timing to the top 3 rows (near WOT where there is little vacuum) and then pull timing when I got into some pinging?

Current curve pulled 5 degrees below 3000 and added 3 back in above 3400. That seems to work, but the car has lost a bit of oomph 2000-3000. I also richened the carb up, so its not going lean anywhere. Going back to the classic holley metering block/HSAB calibration corrected the fuel delivery.

I know from previous testing with my MSD distributor, that the engine will start to ping at 36* at 3000 with heavy throttle and a lean (low 15s) mixture. Confirmed with pepper on the plugs. So I know 36* at 3000 is an upper bound I should stay away from.

[JLMounce]

Originally Posted by chiphead

I'm mainly concerned with near WOT curve for now. Steady road cruise is fairly close. I get 18" at light throttle on a flat road at 2400.

Basically, could I add 2* of timing to the top 3 rows (near WOT where there is little vacuum) and then pull timing when I got into some pinging?

Current curve pulled 5 degrees below 3000 and added 3 back in above 3400. That seems to work, but the car has lost a bit of oomph 2000-3000. I also richened the carb up, so its not going lean anywhere. Going back to the classic holley metering block/HSAB calibration corrected the fuel delivery.

I know from previous testing with my MSD distributor, that the engine will start to ping at 36* at 3000 with heavy throttle and a lean (low 15s) mixture. Confirmed with pepper on the plugs. So I know 36* at 3000 is an upper bound I should stay away from.

Yes you can do that. Same basic tuning technique you would use when adding timing via a mechanical distributor.

Take a stopwatch and make timed runs. Increase timing by 2* and retest. Continue to add timing until the car either doesn’t go faster or goes slower. Then back off 2*

[chiphead]

Wanted to follow up on this.

I went for a 100 mile cruise in 95* heat a few weeks ago to a car show in Georgia.. Car ran really well, no complaints. Engine temps below 50 MPH were right at 180F thermostat. 60-75 MPH, the temp went up to 185-190F. AFR at 70MPH is 12.8-13.2. Sitting in traffic it creeped to 195 but cooled down once I started moving.

I pulled a few plugs after the engine cooled, and I'm seeing a bit of peppering on the insulators. I don't hear any detonation/pinging. The TH400 doesn't like to downshift once it's in Drive. If I'm doing 45, a hard throttle stab to 3/4 throttle will flash the converter to 3600 but it doesn't downshift. So the engine is fairly heavily loaded at moderate RPM.

Looking at my timing curve in the first post, where should I pull timing?