I"m having a bit of trouble with my 850 demon. First, specs on the car and carb. Guessing 3500-3600 84 regal, 430 with SP1 and 284-88h otherwise stock. 15* initial and 33 at about 3200. 373's and th400. I know the intake and cam for this combo aren't the best choice but it's what I have. Regular driving it seems great, no stumbles or bogs. Stabbing the throttle is where I'm having problems. I had 31 shooters front and back and it bogs hard like it's shut off if you stab it from a cruise in high gear. Switched to 35s and it stumbles hard all the way to higher rpms. I have played with the pump cams and shooters down to 28. 31s have had the best feel but I have to roll into the throttle a little slower than a "stab". Was going to check the power valve rating next, I have 14" in park, about 12-13 in gear. Expecting to see a stock 6.5 pv which would be recommended for my vac but was going to try a 5.5-8.5 to see. Right now I'm basically back at square 1 with 31 shooters, looking at the pv next. Am I heading the right direction?
I had a 850 demon on my 350 and 50cc pump on front side cured all stumbling. Never missed a note after that. Shooters, jets, and power valves wouldn't stop it from falling on its face.
My 850 holley did that and I messed with everything. The thing that cured it was accelerator pump cam. A little experimenting and it was cured.
Like mentioned, 50cc pump or pumps will probably solve the issue. Also, for power valves, measure your idle vacuum them install PV's 2 numbers less. eg. if the vacuum at idle is 9 inches, use a 6.5 PV. gary
So far the 31 squirter with the white cam on hole 2 in the secondary has cleaned up almost all of the issue, I need to drive it more to be sure. I got a WB air/fuel gauge that I'll install to help verify what's going on in different conditions.
There is a chart on holley's website that shows the pump cam profiles. Kind of hard to read but is useful. I'll link it when I get a chance.
Add me to the list of guys that had the same problem (mine was a 950) and it was a combo of jets, squirters, cams, but the biggie that finally brought it all together was the 50cc pump. After that the thing was smooth and snappy upon WOT, really a nice running carb. I'm almost regretting selling it....
So after driving more it definitely has been the most crisp setup. Not 100% perfect but not too far off. I was using that pump cam chart as reference and disagreed with some of the data and just started trying different cams after comparing them. Pretty sure I had a pink in the beginning (turned to more clear maybe over time) went to orange, blue, then white as of now. I bought a demon brand pump cam kit though, which if owned by Holley should be the same...
