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Stumble from my 850 Mighty Demon? #69347 06/07/08 07:32 PM 06/07/08 07:32 PM
Joined: Jun 2004 Posts: 192 Maryland D dduster73 OP member
dduster73 OP member D Joined: Jun 2004 Posts: 192 Maryland	73 Duster 440/4speed 9.7 compression rebuilt engine 1 3/4 TTI headers. Stock Holley Street Dominator intake.Comp Cams XE 285 HL hydraulic camshaft 285-297 241/247@.050 545/545 @1.5 rockers.850 Demon carb has 72/80 jets,31 squirters and 4.5 powervalve with 8.5" of vaccuum @800 rpm.Had a 6.5 power valve but no change.Car will stumble @ part throttle when pulling away from a light.Seems to do this at anything under 3000 rpm.Any help appreciated. Thanks ,Dave

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69348 06/07/08 07:49 PM 06/07/08 07:49 PM
Joined: Jan 2003 Posts: 5,444 Indiana Y YO7_A66 master
YO7_A66 master Y Joined: Jan 2003 Posts: 5,444 Indiana	I just checked the Demon web sight and found that a stock 850 MD comes with 85/93 jets. Your 72/80 is almost what a 650 Speed Demon comes stock with. Have you checked your plugs to see if you are lean? Have you tried a 035 squirter? Have you checked to see if fuel comes out of the squirter AS SOON as the throttle moves? 1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69349 06/07/08 07:55 PM 06/07/08 07:55 PM
Joined: Apr 2007 Posts: 1,261 ILL mark7171 pro stock
mark7171 pro stock Joined: Apr 2007 Posts: 1,261 ILL	your driving this car on the street? probably not built for the street and stop and go....no? eehh?

Re: Stumble from my 850 Mighty Demon? [Re: mark7171] #69350 06/07/08 08:05 PM 06/07/08 08:05 PM
Joined: Jun 2004 Posts: 192 Maryland D dduster73 OP member
dduster73 OP member D Joined: Jun 2004 Posts: 192 Maryland	Yes this is a mild street car.Runs on pump gas.The 850 Mighty Demon came out of the box with 80/88 jets, but the plugs were black so i jetted it down.If i just nail it it has a bog.No black smoke out the exhaust.Dave

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69351 06/07/08 08:13 PM 06/07/08 08:13 PM
Joined: Apr 2007 Posts: 1,261 ILL mark7171 pro stock
mark7171 pro stock Joined: Apr 2007 Posts: 1,261 ILL	your gonna get rolled. whats your timming like? itial+mechanical+vacuum... let me guess ... no vacuum advance.... you have a race car. the transitition circuit probably wont cover the demand, and it will be a WOT machine. tim + eric say- GREAT JOB !

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69352 06/07/08 08:16 PM 06/07/08 08:16 PM
Joined: Apr 2007 Posts: 1,261 ILL mark7171 pro stock
mark7171 pro stock Joined: Apr 2007 Posts: 1,261 ILL	Quote: 73 Duster 440/4speed 9.7 compression rebuilt engine 1 3/4 TTI headers. Stock Holley Street Dominator intake.Comp Cams XE 285 HL hydraulic camshaft 285-297 241/247@.050 545/545 @1.5 rockers.850 Demon carb has 72/80 jets,31 squirters and 4.5 powervalve with 8.5" of vaccuum @800 rpm.Had a 6.5 power valve but no change.Car will stumble @ part throttle when pulling away from a light.Seems to do this at anything under 3000 rpm.Any help appreciated. Thanks ,Dave that is not street car specs. i find this makes me laugh.

Re: Stumble from my 850 Mighty Demon? [Re: mark7171] #69353 06/07/08 08:20 PM 06/07/08 08:20 PM
Joined: Nov 2007 Posts: 21,831 Kirkland, Washington Pacnorthcuda Too Many Posts
Pacnorthcuda Too Many Posts Joined: Nov 2007 Posts: 21,831 Kirkland, Washington	Quote: your gonna get rolled. whats your timming like? itial+mechanical+vacuum... let me guess ... no vacuum advance.... you have a race car. the transitition circuit probably wont cover the demand, and it will be a WOT machine. Quote: Huh????? What part of his specs scream "race car only" to you???? While the cam is a little larger than I prefer on a street car, I have run bigger. And with less vacuum (6.5")

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69354 06/07/08 08:24 PM 06/07/08 08:24 PM
Joined: Jan 2003 Posts: 5,444 Indiana Y YO7_A66 master
YO7_A66 master Y Joined: Jan 2003 Posts: 5,444 Indiana	""The 850 Mighty Demon came out of the box with 80/88 jets"" I just checked again and the 850 "AD" Mighty Demon comes with 80/88 jets and the 850 Mighty Demon comes with the 85/93 jets. Does this carb have annular boosters? Is this carb a blower carb by chance? ------------- I found this to be a #5563020GC 850 Mighty Demon Annular Mechanical Secondary carb. This helps explain the smaller jetting. The annulars pull alot more fuel thru smaller jets. If your plugs look good, then I would try raising the squirter size . Last edited by YO7_A66; 06/07/08 09:05 PM. 1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)

Re: youre right it could be? [Re: YO7_A66] #69355 06/08/08 12:09 AM 06/08/08 12:09 AM
Joined: Apr 2007 Posts: 1,261 ILL mark7171 pro stock
mark7171 pro stock Joined: Apr 2007 Posts: 1,261 ILL	my comments are a little raw. your engine that you built should be streetable, because as they say " it runs on pump gas " . people do some strange things to there cars. what package did you try to come close to ... or in between ? look at holleys systemax I,II. or edelbrocks performer, torquer II, or RPM. OR the mopar performance packages in the back of the jobber MP catalogs. mp's suggestions goes to 8.90's i believe...if you still cant come close look at Trickflo's twisted wedge package offerings. Last edited by mark7171; 06/08/08 10:08 PM.

Re: youre right it could be? [Re: mark7171] #69356 06/08/08 07:40 AM 06/08/08 07:40 AM
Joined: Jul 2004 Posts: 3,811 Arlington, Texas B bobby66 master
bobby66 master B Joined: Jul 2004 Posts: 3,811 Arlington, Texas	Get your initial timing around 20 and your total around 36. Make sure you have no vacuum leaks. I run a similar combination and it responds real good on the street. I use the 750 Mighty Demon, though.

Re: youre right it could be? [Re: bobby66] #69357 06/08/08 12:46 PM 06/08/08 12:46 PM
Joined: Jun 2004 Posts: 192 Maryland D dduster73 OP member
dduster73 OP member D Joined: Jun 2004 Posts: 192 Maryland	Yes it has annular boosters.Will try to add more inital timing its at 15* now. Then i'll try 35&36 squirters.If that makes no difference will go back to the 80/86 jets. The cam was chosen by Comp Cams reccomendation.Thanks to all for the advice. Dave

Re: youre right it could be? [Re: dduster73] #69358 06/08/08 01:48 PM 06/08/08 01:48 PM
Joined: Dec 2003 Posts: 5,314 Carstairs, Alberta, Canada dave571 master
dave571 master Joined: Dec 2003 Posts: 5,314 Carstairs, Alberta, Canada	Quote: Yes it has annular boosters.Will try to add more inital timing its at 15* now. Then i'll try 35&36 squirters.If that makes no difference will go back to the 80/86 jets. The cam was chosen by Comp Cams reccomendation.Thanks to all for the advice. Dave I think the timing is your main issue. 15 is waaaaaaayyyyyyy not enough for that cam duration, and that compression. Your inital should be more like 22. If you can set it up for 22-24 initial with 35 total, all in by 2800, I think you will be amazed at the difference FWIW...I have less cam (242@50) with more comp (10.7:1) and I run 24 intial.

Re: youre right it could be? [Re: dduster73] #69359 06/08/08 09:03 PM 06/08/08 09:03 PM
Joined: Oct 2005 Posts: 312 Alberta, Can JUST_N_TIME enthusiast
JUST_N_TIME enthusiast Joined: Oct 2005 Posts: 312 Alberta, Can	make the changes Dave571 said and change jetting to 76/84 w/35 squirters. should make a big difference.

Re: youre right it could be? [Re: JUST_N_TIME] #69360 06/08/08 09:26 PM 06/08/08 09:26 PM
Joined: Jun 2004 Posts: 192 Maryland D dduster73 OP member
dduster73 OP member D Joined: Jun 2004 Posts: 192 Maryland	Okay I'll try more initial timing and go back to bigger squirters. Thanks again for all the help. Dave

Re: youre right it could be? [Re: dduster73] #69361 06/08/08 10:12 PM 06/08/08 10:12 PM
Joined: Apr 2007 Posts: 1,261 ILL mark7171 pro stock
mark7171 pro stock Joined: Apr 2007 Posts: 1,261 ILL	if its NOT timming and IS the carb...it will be a lean problem. cover it up with a longer pump shot. it will deliver the fuel its not pulling for itself. get you past and on to going fast. a smaller squirter, or larger 50cc pump , can accomplish this as well as bumping the pump cam around till it lasts longer.

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69362 06/09/08 12:37 AM 06/09/08 12:37 AM
Joined: Feb 2007 Posts: 5,080 organ M maximum entropy master
maximum entropy master M Joined: Feb 2007 Posts: 5,080 organ	Quote: 73 Duster 440/4speed 9.7 compression rebuilt engine 1 3/4 TTI headers. Stock Holley Street Dominator intake.Comp Cams XE 285 HL hydraulic camshaft 285-297 241/247@.050 545/545 @1.5 rockers.850 Demon carb has 72/80 jets,31 squirters and 4.5 powervalve with 8.5" of vaccuum @800 rpm.Had a 6.5 power valve but no change.Car will stumble @ part throttle when pulling away from a light.Seems to do this at anything under 3000 rpm.Any help appreciated. Thanks ,Dave mighty demons are calibrated for larger cams. your cam should be big enough for that carb to work properly. every demon carb i've ever worked on has been full of metal chips from manufacture. in the main wells, everywhere. first you need to make sure that thing is absolutely clean. if it's mainly street driven and the plugs are black, it's most likely idle mixture. that carb does not have an intermediate circuit. make sure your float level is good. does your carb have idle ez? what kind of torque converter do you have? mighty demons are almost impossible to tune if your stall speed isn't high enough. for what is the good life if not doing things thoughtfully?

Re: Stumble from my 850 Mighty Demon? [Re: maximum entropy] #69363 06/09/08 06:22 PM 06/09/08 06:22 PM
Joined: Jun 2004 Posts: 192 Maryland D dduster73 OP member
dduster73 OP member D Joined: Jun 2004 Posts: 192 Maryland	The car is a manual transmission.There is a screw where the air cleaner stud goes, and it did come with an addendum paper work on the idle ez, but adjusting the center screw does not make any difference.I adjusted the idle settings using a vaccumm gauge for highest vaccumm.I adjusted the float level to the middle of the site glass.When i jetted it down i pulled the bowls and metering blocks off and it was very clean.I will try the suggestions one at a time when i get back to the garage. Thanks again, Dave

Re: Stumble from my 850 Mighty Demon? [Re: dduster73] #69364 06/09/08 11:16 PM 06/09/08 11:16 PM
Joined: Jan 2004 Posts: 9,066 Eugene, Oregon M minivan master
minivan master M Joined: Jan 2004 Posts: 9,066 Eugene, Oregon	A friend just installed a mighty demon on his Olds race car.. His carb came with the wrong jets and when he called Barry Grant, he was told the specs were incorrect.. Might want to call yourself....

Re: Stumble from my 850 Mighty Demon? [Re: minivan] #69365 06/10/13 11:18 PM 06/10/13 11:18 PM
Joined: Mar 2013 Posts: 571 Spring Hill Fl 65Fury440 mopar
65Fury440 mopar Joined: Mar 2013 Posts: 571 Spring Hill Fl	I just put a mighty demon on my 440 with lumpy cam, Edelbrock Performer RPM intake, 1 3/4 headers, MP electronic ignition, 4 spd car, The previous owner took out the primary power valve and blocked it, secondary also blocked. The carb has 86 primary jets,88 secondary. It doesnt run bad, but is running rick just driving normally. The plugs are dark tan, is there alot to gain by putting in the PV and dropping the jets down 8 or so sizes?

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