DEMON 750 secondaries jet size ?

[skip68]

I got a DEMON 750 mechanical second, no choke carb.  I had it open and saw that the jets for the secondaries are 96's.  Is that too big ?  I don't remember the size of the primaries but it runs great until you get into the secondaries.  It seems to not have as much pull as the primaries and so I was wondering if the jets are too big and it's getting too much fuel ?  Thank's,   Chuck.........

[mopar_nut_440_6]

I do not know your build but I used to run a 750 Holley DP on a 440 AT with a 509 cam fairly well dialed in and if I recall correctly it had 78 primaries and in teh low 80's for secondaries.

[skip68]

440 30 over = 446, custom cast closed chamber heads like Indy, 10.25 to 1 Comp. Ratio,  Ross race pistons,  509 292 cam,  crane gold roller rockers,  forged steel crank,  Torker II single plane intake,  DEMON race 750,  electronic ignition with chrome race box,   Automatic with shift kit,   2.76 open rear that will get changed to a 3.23 sure grip.   I have a feeling I'm jetted to large in the secondaries with those 96 jets.      The car pulls great on the primaries but just doesn't have the much more punch in the secondaries.    Thank's,     Chuck...........

[mopar_nut_440_6]

440 30 over = 446, custom cast closed chamber heads like Indy, 10.25 to 1 Comp. Ratio,  Ross race pistons,  509 292 cam,  crane gold roller rockers,  forged steel crank,  Torker II single plane intake,  DEMON race 750,  electronic ignition with chrome race box,   Automatic with shift kit,   2.76 open rear that will get changed to a 3.23 sure grip.   I have a feeling I'm jetted to large in the secondaries with those 96 jets.      The car pulls great on the primaries but just doesn't have the much more punch in the secondaries.    Thank's,     Chuck...........

That is basically the same build as I had except I ran 4.56 gears and a Holley street dominator intake and 750 DP. IMO you are really rich. I have not ran this engine in 12 years so just going by memory! I would pick up a Holley jet kit as this will give you a variety so you can dial it in. I have had no experience with the Demon carbs so somebody else will likely chime in and set you straight.

[skip68]

Thank's.     4.56 gears     Man I bet that car just lit up the tires and was real quick.   

[firefighter3931]

Chuck, the jetting is waaay too fat on the secondaries. I bet that if you did a full throttle blast and shut it off immediately the plugs would be black. 

I would jet down to 80's and start from there. That cam profile also needs some gear and stall to work well. I would be looking at at least a 3200 stall and 3.91 gears....otherwise it will be a slug out of the hole. 


Ron

[skip68]

Mikes going to hook me up with some gears soon.  I put a B&M 3000 stall in it last year.   80's,     Will a holley jet kit work in a DEMON ?   Thank's Ron.   

[mopar_nut_440_6]

Thank's.     4.56 gears     Man I bet that car just lit up the tires and was real quick.   

It actually hooked pretty well for what it was! Stock suspension (318 car) , air bags and an adjustable pinion snubber (I was on a budget and this is what I had). Ran 12.8 @ 110 with slicks! Stock convertor so it was on the lame side out of the hole.

[skip68]

12.8 at 110 is not bad at all. 

[mally69]

YES, demon carbs use holley jets. 

[skip68]

Thanks     I'll go check out some kits.   Thank you all for the help.     Chuck............

[Chryco Psycho]

the added screw up here is that Demons are not numbered the same , I remember jetting a demon & wnet 3 sizes larger with Holey jets & it leaned out

[skip68]

    So I guess high 80's would be a place to start with Holley jets ?     Can I tell by looking at them that they are smaller ?

[mopar_nut_440_6]

   So I guess high 80's would be a place to start with Holley jets ?     Can I tell by looking at them that they are smaller ?

If it was me and I was worried about it I would probably start with an 86 jet, make a hard run, pull a plug and see what it tells you. I would suspect that you will still end up being close to an 80 but I have never ran a Demon so the characteristics and jetting may be different than the standard 477X Holley. It is better to be rich than lean and jet changes are quick and easy. Let me know how it turns out!

Cheers,

[skip68]

86 sounds good.     I'm going to the speed shop today to get some jets.    

[ronv]

I have always had great success with Demon Carbs. I changed the air bleeds in my mighty demon 850 and got the o2 #'s in line. This produced 15 more hp on the chassis dyno. If you have access to a chassis dyno I'd recommend using it. It's a great tool.