Quadrajet running lean after head and cam swap

[bcarlson78248]

Thanks again, Cliff.

I put it the carburetor together and having it running, so there are a few more items to tweak.

I tried to check to see if the APT needs adjustment, using the tip-in procedure in the book.  When I had it running at about 2000 rpm and then pushed the choke nearly closed, it took about 1-2 seconds and then the idle starting going up.  However, it went up more than the 50-100 RPM described in the book - probably closer to at least 300 rpm.   Maybe I'm not doing it right.

I set the idle and then took it out for drive.  It starts, idles and pulls extremely well and very evenly at part throttle.  Everything seems to work smoothly and power comes on quickly.

When I went to full throttle acceleration it also pulled well, but I noticed that under hard acceleration the AFR stayed at about 14.0.  IIRC, with my old settings the AFR would go to about 12.5 or lower when the secondaries kicked in, but maybe I'm mixed up.   I have the air door tension set to about 1/2 turn after removing all free play and it moves freely. I also checked the secondary throttle plates, and they do open to 90 degrees when the accelerator pedal is floored.  Should I try setting the spring tension a little looser?

Bruce

[Cliff Ruggles]

Tune the idle mixture first, then the APT.  If it runs and drive good on the primaries and idles fine you are done

Once the primary system is fine tune the secondaries by changing metering rods for best power at full throttle.  The spring setting is for smooth transition not how much fuel it adds.

It's difficult to tune WOT without a dyno or drag strip.  I don't have much faith in A/F meters, tuning for best results is the goal.  You can usually get close with "seat of the pants" assessments, but to really dial in an engine for best power at full throttle one really needs to be able to measure engine/vehicle performance.......Cliff

[bcarlson78248]

The APT is 3 1/2 turns out, and the idle screws are 3 1/2 turns out.   Idle is stable at about 650-700 RPM in drive (TH350).

When I tried using the APT tip-in procedure at 2000 rpm I'm not sure I was doing it right.  There was no immediate change in RPM when I pushed the choke plate nearly closed, but then after 1-2 seconds the RPM started to rise and went up at least 200-300 rpm.   

I understand the concept of the APT, but I don't understand what to expect when I change the settings.    For example if I screwed it in another 1/2 turn, what change would I expect to see?  Or should I just leave it alone?

Thanks,

Bruce

[Cliff Ruggles]

Don't worry about the "tip-in" test.  If it's working good put some fuel thru it and evaluate engine performance, fuel economy, etc.  You can make very small adjustments to the APT and see if they make things better and always return to the original settings if they don't.....Cliff