EvilCartman

iTrader: (1)

Started on getting the Mighty Demon 850 tuned for driving around town. Driving along on a very slight incline keeping at a steady speed the car runs fine. Try to speed up a little bit and it runs really rough or if you try and go up a steeper hill. If you go WOT, it stumbles around for a half sec then takes off like a bat out of hell. Idle doesn't seem excesivly rich, throttle blades are set per BG's specs, stock PV of 6.5 is back in it. It did the same stumble with a 4.5 PV. To me it is pointing to the PV circuit just because of the cruise problem, but would like another opinion. I'm running a 35 tube style squirter front and rear plus a blue pump cam on primary and pink on secondary. Also have 31 tube style squirters I can try out too. The eze-idle adjust thing is closed off for now, didn't have it in the 750 I had before and it ran fine.

I went through the carb tonight tweaking on things and cleaning out more junk they left behind. Took too huge metal chips out of the vent tubes. Checked the idle and high speed air bleeds and they were not to spec so I made them to match spec (used a gauge pin and proper drill size). One of the high speed bleeds wasn't even tight! Soon as I put the screwdriver on it, it moved. I reset the throttle blades to be a little better fitting in the bores and tweaked them a bit to have both transision slots even. Went as far as to smooth the inside of the boosters where there was a parting line left plus some burrs at the tube opening. Drove the car after all of this had been done. Getting a hold of a vacuum gauge tomorrow, with the 750 it used to pull 12 inches.

EvilCartman

iTrader: (1)

Welp, thanks the great response to my question the car is running better now.

sofakingdom

iTrader: (1)

Glad to be of service.

Your power valve sounds like it's WAY too low of a number. What makes the stumble, is that it doesn't open until the throttle is nearly WFO; so under all conditions from near cruise on up to WOT, it's too lean.

Try using one that's about 2 #s below the vacuum idling in gear. So if you have 10" idling in gear, use a 7.5 or 8.5; etc. That'll make it open sooner as you slowly ease into the gas, and fix the lean stumble. Also, try using less centrifugal advance, and more static advance, but of course the same 34-36° of "total" advance; so try something like 22° static and 12° of centrifugal, instead of 10° of static and 24° of centrifugal. That'll get your idle vacuum up so you can use a higher PV so you can eliminate the tip-in sag even further.

Lots and lots of people have complained about Demon's QC. They have a great design, but evidently their mfr has very poor execution. Metal chips in the passages is one of the most common defects people talk about.

EvilCartman

iTrader: (1)

Woohoo a response! thanks. Yup, I went with an 8.5 PV and it's still not quite right but a hell of a lot better. idle vacuum is at 12", was 10" before messing with the idle mix screws. Timing is actually locked out to I think 38 degrees right now, been running with locked timing for probably a couple years now.

Quality Control definitely has gone to the crapper that's for sure. Think I'll write an email to them even though I doubt anything will come of it. My old 750 Demon had a chip here and there but nothing like the current one. Went through and checked the primary metering block and it had a bunch of burrs left in it and one of the screw in restrictors was loose. Went through the thing and cleaned it all out plus made sure all the holes I could get to were free of burrs. Need to do the same to the secondary side now. For what I paid for the thing, I can't believe all the stuff I've found not to my liking.

xpndbl3

iTrader: (5)

yea demons have really turned to crap, which is what made me buy the proform carb instead. I pulled a buddies proform apart and every hole and oriface was perfect and no chunks of aluminum like his demon that he bought. Great carbs but I wonder why they don't blow out each hole or tank them or something....probably one of the penny counters in management

EvilCartman

iTrader: (1)

One other thing I found was the boosters weren't even centered in the hole so I had to tweek that too. By the time I get everything taken care of, I'll probably have 500 bucks worth of my time just cleaning and fixing this carb up Oh well, last Demon I'll ever buy new.

five7kid

iTrader: (14)

It would seem that Barry Grant has been spending too much time DNQ'ing in Pro Stock and not enough time watching the shop. I haven't seen his name in the past 3 or so races, maybe he's seen the light and will go home and re-establish the quality that established his initial reputation.

I think both he and the racing public would benefit if he did.