I just found (actually was told about) this thread and have read the whole thing. Wow - what a trove of information. Thanks Tom!
I'm "right now" in the middle of trying to get an AED "850" HO Annular dialed in on my 69 GTO. It's my first experience with a Holley platform so my learning curve is steep. It's on a Northwind single plane on a 461 stroked 400, solid roller (251/257 @ .050, 110 LSA, 106 ICL, .620 net lift at the valves after adjusting for lash), 10.3:1, 72 cc Edelbrock round port heads, 2.190/1.77 valves, TH 400 w/3100 rpm converter, 3.50 gears, 27.7" tall Nitto NT555-R's. I just got the engine back together and running recently after being down for "awhile" (long story) and made the aforementioned changes as part of that. Previously it had less cam (236/242 @ .050 - .010 less lift) less compression (10:1) running a real 455 SD QJet on a Torker 1 (only intake I had at the time that would cover the ports in the heads).
I have an AEM X-series digital A/F meter in it. Out of the box it was really rich everywhere, especially at part throttle light cruise - A/F in the 9's-10's all the time, and it was actually a little leaner at WOT but not by much. The carb out of the box came with 81/91 primary/secondary jetting, 4.5 power valve on the primary side only (secondary has a plug), .035 pump nozzles, .070 idle air bleeds, .031 high speed bleeds, and .035 idle feed restrictions in what thanks to your thread I now know to be the less than ideal "high" location on the metering blocks. I struggled with it for a good while before finally making some progress with it. Already I've changed the oil more than once due to it smelling like fuel.
I've been able to do a lot to get cruise mixtures to where I think they should be - 13's-14's even occasionally low 15's - that AEM meter reacts really quickly, and one thing that has been a surprised is how widely the mixture varies even under what I'd thought would be steady state.
What I've changed so far:
Idle air bleeds: .084
Jets 76/86
Idle feed restrictions .031
Idle RPM 950 in gear , mixture screws 1 3/4 turns out - gives me a meter reading in the 13's-14's. and 10" of idle vacuum. It's amazing to see how large an effect even 100 rpm of idle has on vacuum and also mixture reading. It's dramatic.
WOT is still fat, 11.9:1 - thinking I might go down one more number on the jets in both ends.
Plugs are looking decent - medium brown coloration now (93 octane unleaded), whereas before they were sooty black (duh)
I've also got Dave Vizard's Holley book and have been studying that.
Should I "move" the IFR to the lower location you think? Do the changes I've made so far make sense?
Thanks,
Bear
|