Annular 80514 HP1000, I'm close, which way to go?

[HarrysTaxi2]

[Right hand drive]

[dave brode]

Gents,

I appreciate the comments/input. However, my issue is not with the main circuit. Although, I do sometimes want to throw the afr gauge away. Black plugs don't lie though.

When I get done with the 4781 experiment, I may well go back to stock on the 1000 just to see.

Pinion seal is leaking badly, might be a delay.

Thanks, and feel free to back and forth.
Dave

[Right hand drive]

[BradH]

I'm definitely following along w/ this thread. I have to say that I'll take drivability over "perfect" -- whatever the He11 that means -- AFR readings. Too many people seem to drive themselves bug-nutz tracking their AFRs and get bent outta shape when they can't get their combination to run some particular AFR. I'll have a wideband O2 on my car for the first time when it's back on the street 'cuz I want to be able to see trends from upcoming tuning efforts, but not shooting for any specific #s.

[Right hand drive]

[FC-Pilot]

You guys have definitely made me do some thinking. I have played on the dyno with an annular booster 750 holley on a 350 sbc. We made just shy of 50 pulls on that engine with three different carbs. We had over 20 pulls just on the annular carb playing with emulation and air bleeds along with jet changes. For sheer power, it liked one e-bleed up high at .028 if I remember correctly. We tried old holley setup with two .028 and a few others with three bleeds. We also tried a bunch of air bleed sizes with each one. Now the downleg the we ended up leaving on the engine due to better HP numbers liked two bleeds at .026 if I remember correctly. It liked a .034 air bleed (or something close, I don’t remember all the details as it was years ago). Now, all this was done on the dyno looking for power, not drivability. This was also a pump gas 7500 rpm small block, so it did not fit into the race category, nor the typical street category either. Now I need to do some more testing to get a better grasp on what all the numbers were telling me. Thanks for stirring my brain, I need it every now and again.

Paul

[Right hand drive]

[FC-Pilot]

We were concerned with power numbers between 5000-7000 rpm’s. We saw an increase in both peak and average in that range. This was for a boat that we knew would slip the prop till about 5000 anyway. Almost like having a torque converter stall to that level. The style of boat is accustom to having 600-1200 hp big blocks in them, so being only 482 hp was creating a very fine line for boat setup (which was much trickier than carb calibration). Down that far on power meant that we needed every bit we could get. Again, we never played with this stuff in the boat. Once it went in the boat we have not touched much as boat setup at this point produces better results than trying to find one more HP.

Paul

[dave brode]

Hello Gents,

I have too many non car fun irons in the fire. The pinion seal is still leaking but I am still fooling with the 4781. You'll see that I went all over the place here, but I believe that I've stumbling in the right direction.

Just for fun, I reversed the bypass air setup on the sec side, went back to normal 2 corner idle, .020" constant feed hole on sec side. Still .035" ifrs. About the same, rich at light throttle in 2000rpm range. Too far in on idle mix screws made for lean sag, as before

Went to .038" IFR on primary as an experiment. Light throttle rich issue a little worse.

I have never felt the need on anything before, but in desperation, I locked the timing out, WITH 16 or so more from vac adv,. [Was at 22 initial / 36* total, plus 16 vac]. Bingo. Much improved. I've never like the locked timing idea on the street, but I'm impressed. Still had rich spot at 2000 rpm level ground and esp on slight decel, but much better. Engine happier. [still .038" PIFR]

Still stabbing in the dark, and dwelling on the sec side constant feedholes, I did poor man's 4 corner idle, 1/16" passages. Plugged sec side constant feed hole. Closed sec throttle plates. Idle mix screws a little more responsive. Rich spot maybe a tad better, I suspect due to the constant feedhole being gone. Decel afr leaner [good for mileage?]

Today, went from .038" to .035" pri IFR. Rich spot almost acceptable, going into the 12s if you try to make it, improved from 11s and occasional high 10s. 2 turns out, idles good, snappy off idle. 1.5 turns "ok", 1.25 turns quite engine unhappy at idle. Changes in idle screws don't have as much effect on rich spot as the umpteen other combinations.

I'm glad that I had the $100 4781 to use as a learning tool. I was really discouraged, but the last three changes made me go whew! I could live with it like it is, shelf it and go on to the 1000 hp, but I'll try a little more. I'm leaning toward .033" ifr. If that doesn't work, maybe try primary TSR. Thoughts?

Thanks for the insight.
Dave