Fine Tuning a 360 Magnum with a Brawler "Double Pumper"

jmanhoff said
Right now I have a 35 shooter, went up from a 31 that came stock. Still have the stock white cam.

The stumble happens when I'm off the throttle and quickly get into it. For the most part, if I'm already down on the throttle a tiny bit and I quickly press it, it revs up with a very slight hesitation. If I'm fully off the throttle and I smash the gas it cuts out and then goes.

Doing Dominos, I can get a lot of different scenarios knocked out in a short span of time which I guess is useful to a point lol. If I ease into the throttle it doesn't hiccup at all, it's just anytime I remotely quickly get into the gas.

I think it's difficult to get that pump shot figured out because it's a relatively light truck with a really short first gear, and a bunch of torque so it gets moving quickly. If I was to try to fully open the primaries and try to get moving fast, I guess the best way to describe what the engine sounds like is puh-WAHHHH *shift* puh-WAHHHHH. (The "puh" being a cutout lol, it throws you forward into the wheel and the nose drops, then the other circuits catch up and then it throws you backward into the seat)

I don’t use 35’s on anything that isn’t a tunnel ram or a carb that’s far too big and poorly tuned.

I’m still trying to figure out if it’s going lean on tip in or if it’s fat. I’m leaning towards it’s going rich but I’m not sold on it yet. I’m still thinking.

One issue is if you are cruising and you just lean into the throttle and it stumbles is different from cruising along and sticking your foot through the floorboards and it stumbles.

The former will never get cleaned up from pump shot. You can test this by holding the engine at cruise rpm and then just ease into the throttle and you’ll see the fuel just pee out of the squirter.

The less aggressive the pump cam and/or bigger nozzle will make it worse.

I’m talking about with the car parked and you running the throttle by hand to see that.

The other thing is main air bleed size. The main air bleed controls when the booster starts. A bigger main air bleed starts the booster sooner so it will be richer sooner. There is overlap between the T slots and the mains. Start the booster too early and they get rich.