Jetting a speed demon
 

I have a zz502 and it came with a holley 850 vacuum secondary carb. I yanked it off and installed a speed demon 850 mechanical secondary carb. Right now it is jetted 80 primary/88 secondary. I think the primaries may be ok but when I open the secondaries I think it is getting too much fuel. Any ideas what jetting might work best for this application? Street driven..no racing... well,not on the track anyway :D Thanks

My experience has been that Demons are way too rich out of the box, typically by about 6-8 jet sizes the primary side and even fatter on the secondary side; usually I end up having the secondary jets about 4-6 sizes bigger than the primaries.I've messed with over a dozen Demons, both Road Demons, Speed Demons, King Demons, and a couple of their 6-shooter setups and they were all pig-rich as delivered.

It's hard to say without driving your car and checking the plugs but my guess is you'll end up somewhere around 76/82 for jetting, probably even a little leaner.

Also, if it's a brand new Demon completely gut it and clean it-- you might be surprised how many burrs and debris comes out of the main body/airbleed passages/metering blocks... it can cause all sorts of driveability issues depending on where the "junk" goes and what it clogs.

Thanks for your reply.. The carb is used. It came off a buddy of mines 496 which is putting out about 650hp so I'm sure it will need to be jetted down. I may try going 78/84 and see how it works out. Right now it is at 80/86 and it is rich so I may swap them out tomorrow and see how it works out.. Thanks again :D

Cool. Just keep an eye on the plugs and wideband (if you have one.)

Don't forget your powervalve/shooter/etc requirements may be different too.