Calling all Holley guys!

[msbaugh]

Ok. I've made some great progress but need a little bit more advice. Help me get this thing 100%.

I tracked the WOT lean condition down finally, but still have a long to do list. It turned out to be an ignition issue    I had a spark plug or two that weren't keeping up and a boot that had burnt through to the metal underneath the heat covers. I was thinking about it completely wrong. These a/f meters measure O2 content in the exhaust. So the fuel was there, it just wasn't getting a complete burn causing 14:1-17:1 readings. Now I'm good at WOT... running like a bat out of hell!

The issue is that I still get a bad lean spot when hitting the throttle before the secondaries start to open. I jetted the primaries up 2 more (73 to 75) and it got wayyy too rich cruising part throttle that it started surging. Went back to 73.  I also upped the squirter size on the primary from 31 to 32, no big change. Should I put a cam on the primary that has more lift early on?

I have new power valves on the way. I idle in drive between 7-8 inches. I have a 6.5 PV in now on both and will try 4.5s and maybe 3.5s when they get here.

Any advise here is appreciated. Maybe I just need to do more experimenting.

I wish I could have the secondaries open a little sooner.  On another note, fuel pressure is steady at 6 psi and fuel pump pushrod is good. But I have vapor lock when idling too long. It drops to 2-3 psi, but clears when I get some airflow cruising. I'm going to do some re-routing, move the regulator further away from the headers, and go crazy with some thermo-tech heat shield.

[jimynick]

I think you're on the right track with the shooters, but if memory serves, I think Holley recommends you go 3 steps for each change. The other thing would be the pump cam and there's a kit made with a variety of different cams that change the amount and duration of the squirt. There's also a recommended clearance between the pump arm and the linkage, but I can't remember what it is- somewhere around .015" maybe. Congrats on finding the ignition foibles! On to the next! 

[734406pk]

Are you running a 50cc accelerator pump?

[msbaugh]

Are you running a 50cc accelerator pump?

No, the 750 HP double pumper I have came with 30cc pump/diaphrams.  They do sell a 50cc conversion kit that will work...  but hopefully I can avoid spending the money and get it right with jut squirters and a pump cam change out.

I've got a high stall and 3.93 rear gears in this car so it needs the extra fuel pretty quick.  Are there guidelines to when you should need a 50cc pump?

[734406pk]

Sorry no guidelines, RB's like a lot of fuel. I would recommend a 50cc kit on the primary and you can change the squirters and cams to suit your needs. The squirters only change the time it takes for the fuel to inject not the volume. Check the Holley site for accelerator pump adjustment procedure. Full throttle opening you should have .015" clearance from bottoming out your acc fulcrum lever. This is a process to tune a carb but when its right you will be happy.

[msbaugh]

That might be the key with the 50 cc primary pump!  I'm not sure. I took the 6.5 Powervalves out and put in the 4.5. On both sides. I'm lean as hell now to the point where it's worse than it's ever been. Once the secondaries open up I'm good but it's soo lean before they open, that I can barely even get there.

I don't know what way to go now. The whole half your vacuum or minus 2 " trick hasn't worked. Either I leave the 4.5s in and jet up again on the primaries, or I put the 6.5 PVs back in and try the 50 cc pump for the lean primary spot.

Maybe there's several different ways of getting to the same place. I just need to adjust the right thing one at a time. I understand these more and more as I go on its just difficult to bring it all together.

[734406pk]

That might be the key with the 50 cc primary pump!  I'm not sure. I took the 6.5 Powervalves out and put in the 4.5. On both sides. I'm lean as hell now to the point where it's worse than it's ever been. Once the secondaries open up I'm good but it's soo lean before they open, that I can barely even get there.

I don't know what way to go now. The whole half your vacuum or minus 2 " trick hasn't worked. Either I leave the 4.5s in and jet up again on the primaries, or I put the 6.5 PVs back in and try the 50 cc pump for the lean primary spot.

Maybe there's several different ways of getting to the same place. I just need to adjust the right thing one at a time. I understand these more and more as I go on its just difficult to bring it all together.

The power valve number is where in the manifold vacuum range they open and enrich the air fuel mixture.  Therefor the 6.5 power valve opens sooner than the 4.5. The 1/2 idle vac setting is just a guideline and further tweaking may be necessary. I would first install a 50cc primary accelerator pump and a 40 squirter nozzle then tune from there.  For a big block that is. There are 4 fuel circuits for the Holley as I see it: idle mixture, accellerator pump, main metering then power valve and beyond that is secondary metering etc. They all need to transition smoothly For the best performance. It takes time and patients, but this is carb tuning !