I have a 383 IROC with a ZZ-9 cam and a 'NEW' Holley 4150 model 4777, 650cfm DP with mechanical secondaries. I switched the two squirters to .037 before I raced it last Saturday, jets are still stock at 67/73. My idle and cruise performance is great, maybe a bit rich. I have an O2 gauge that helps to tune. At the track, I have a slight bog at launch (2,800 rpm) and at each gear shift (5,900 rpm) when I go to WOT. If I ease it to WOT it runs supreme!!

I suspect that it is a lean bog when I go WOT too rapidly. My stock PV is a 6.5. Should I go to an 8.5 and up the jets to 75 on the secondary. I just swapped in .040 squirters, but I have yet to test this setup.

ANY OTHER suggestions from you Holley guys???

Happy New Year!!

Thanks

Just get your pumps dialed in right. Experiment with different pump cams, and go to larger or smaller squiters if you have to, and make sure the adjusting screw on the end of the pump arm is set right. Use the O2 gauge to determine what you need.

However be warned that the o2 gauge has it's limits. If it's a very very rich bog, it will just read lean, so use common sense. I had a guy once come complaining to me about a terrible lean bog he couldn't seem to get rid on on his mild 305. Turns out he'd gone to a 50cc pump and huge squirters..and couldn't figure outwhy his o2 gauge kept reading lean when he floored it.

Pay attentiuon to the gauge while easing into it...see if it tends to go lean or rich.

A 37 squirter is pretty big. Holley suggests going to a 50cc accelerator pump when using a 37 or higher squirter. But that's not gospel.

First, find out if it is a lean bog, or as I suspect, a rich bog.
If it's a lean bog, you should be able to attach a rubber hose to a propane bottle, stick it in the primaries and open up the valve, and when you rev it, it won't bog anymore. If it bogs worse, then it's not a lean bog.

Also, a lean bog will tend to run better when the engine warms up, but a rich bog will tend to run better when the engine is cool.

And everytime you change the accelerator cam, make sure you reset your accelerator pump lever arm adjustment. I like to go for zero lash. The cam determines how much fuel dumps out the squirters WHILE the primaries open up.

My suspicion is that the 37 is way too large. Why? Because my 465 cubic inch built Pontiac in my Firebird likes a LOT of fuel, but a 37 is too large for it, and that's almost 80 more cubic inches.
When you change squirter sizes, jump about 3 sizes. You can fine-tune later, after you know you're going in the right direction.
If I were you, I'd try a 34 squirter. If the bog gets better, go to a 31 squirter. Then you have to try different accelerator cams to give you more or less of a fuel shot as the primaries open, depending upon what your engine likes.

Let me know how that turns out.

Take the carb spacer out and mount the carb right on the manifold.
This will reduce the plenum volume and increase throttle response. This will also return your manifold to a true dual plane design, increasing bottom and lower mid range torque. In this cool winter weather you may need richer jets as compared to hot
summer days. The primary jetting should be close but I'd try
richening the secondary side. If there is a powervalve in the secondary side, go with 75 to 77 sec jets. If there is no secondary powervalve, start rich (82sec jets) and work down
to around 76 to 78. Secondary jet extentions and notched floats
may be required, also try raising the secondary float level a little more. (jet flow will start sooner). For full throttle acceleration
the value of the powervalve is irrelevent because as soon as you mash the throttle open, vaccumm drops to 0 and all powervalves will open instantly. For jetting let your 1/4mile MPH lead you
to the best setup and the 60' times to tune the accelerator pump(s). After you give this stuff a try you'll most likely won't need
that big an accelerator shooter.