Demon carb questions

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74desertduster

74desertduster

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So I have this Dart Sport with a 360 and Magnum heads with headers. Don't know the cam but she's a good runner. Intake is a Mopar M1.

Anyway, it has this Demon carburetor on it and I know nothing about them. This one will stall if I brake too hard or corner hard but I don't know if that's normal or not.

Was wondering how hard it would be to switch to an Edelbrock carb as far as intake/linkages etc. and if this Demon carb is worth anything?

Thanks!

Brian

CARB.JPG


CARB2.JPG
 
Sounds like you float is set to low......jets get uncovered during hard manuveurs and it stalls the engine. Also check the fuel pressure.
 
A lot of people hate Demons. Most of them hate them because they don't know how to tune them or don't take the time to tune them. My 850 Speed Demon ran like crap straight out of the box, but after a day of tuning it starts and runs better than any other carb I've had. The Demon is essentially a revised Holley, so many of the tuning tips and tricks apply.
 
I'll trsde you eddy 750 performer,6 months old straight across.
 
Demon carbs. are very very finiky,if you don't have experience tuning a carb don't buy one..i had one years ago when they first came on the market,biggest piece of crap carb i ever bought,and i do know how to tune them.finally got this one running pretty decent just as i was selling the car,Edelbrocks aren't much better..handsdown,if you want a GOOD carb. worth every penny you spend on it get a Quickfuel,i was amazed how well it performed right out of the box,and has improved the performance of my car,everytime i tune/play with it but for the most part i really haven't needed too...
 
Looks like you have a Lokar(?) aftermarket kickdown cable and bracket - you should have some adjustablity with that to make it work. the carb itself will bolt right on. you'll have to fiddle with the carb fuel line - I think the Eddy is a single feed.

BTW - I went from Eddy to Demon on my big block. I love the Demon - before you go buying a new carb, I'd give it a once over to tune it properly.
 
It runs fine other than the stalling on hard braking and it doesn't have a high idle when cold...I haven't even looked to see if there is one and it just needs adjusting and the choke etc...

I guess Im just more familiar with the Eddy carbs and was thinking about a swap...
 
Sounds like the float is way too low on the demon. When it comes to Demons you have to make small adjustments. On a Holley I would say go a whole turn on the air/fuel screw. On a demon that would be a 1/4 to 1/2. The precision milling makes them very touchy.

Nice thing about the Eddy is it is mostly a bolt and go. Just be aware that you will not be getting all the power out of the engine you get with a Demon or a Holley.

Dan...
 
To me it sounds like the float level is too high. What you describe I've seen many times on Holleys I've tuned. Thats is the carb floods when you brake or turn hard from the too much fuel in the bowl. If the level was too low it'd run dry under hard acceleration. There is a fast idle adjustment also. I would check that and check the float level. Or rebuild it and start over. Unless of course you really want an Edelbrock.
 
I realize this is an older post...been chasing other things and going through a split with my wife.

Anyway...started messing with the carb a bit today and the float levels look good.

I am wondering about my fuel pressure. At idle I am 3.5 lbs and the manual doesn't really say anything other than most race engines can perform at between 6 and 7 lbs...

Am I too low? Has a bit of stumble at takeoff...acts like an accelerator pump.

Thanks folks!
 
74desertduster said:
I realize this is an older post...been chasing other things and going through a split with my wife.

Anyway...started messing with the carb a bit today and the float levels look good.

I am wondering about my fuel pressure. At idle I am 3.5 lbs and the manual doesn't really say anything other than most race engines can perform at between 6 and 7 lbs...

Am I too low? Has a bit of stumble at takeoff...acts like an accelerator pump.

Thanks folks!
Click to expand...

Is your intake a dual or single plane and have you got a spacer between it and the carb, is it open or 4 hole. You say your fuel pressure is 3.5 at idle, what is it at 4000 rpm. Either way you should have 6 psi across the entire range. What kind and make of fuel pump are you running. This low pressure will not cause the stumble at takeoff but will cause problems at full.
 
Ok..pressure this morning was about 3psi through the rpm range to 4000 rpm

Sometime fluctuated lower.

Fuel pump and filter change? Appears to be a stock mechanical fuel pump.

pressure.jpg
 
Ok..changed the fuel filter and still have 3 psi across the board...so I think I am down to a fuel pump or a bad gauge.

Unless they put a regulator someplace on the car I don't know about.
 
Demon recommends against running jet extensions on a street carburetor because they say the car will stall out on hard braking.

I'd see if you've got those in the secondaries, pull them, and see if the problem goes away.

That Demon will run the balls off of an Edelbrock carb any day of the week if its set up right.

Steve
 
FYI, A lot of gauges read low when they get hot, but then again, you might need a fuel pump.

The book "How to Tune and Win with Demon Carburetion" is a really good read for Holley and Demon carbs both.

Good luck

Steve
 
OK...for 17 bucks I changed the fuel pump. Still reads about 3.5 lbs so will look for a gauge or see if this one is blocked by dirt something.
 
Stock tank, pull the sending unit and check the sock. It might look like this...

pickup.jpg


The car that came out of ran, just not real well!

Also, make sure none of the lines are collapsing under suction.
 
i think they say about the middle of the site glass-float adjustment.
yes you should have 6psi, 3psi is crap.

is that the manifold vacuum you have hooked to your vac advance?

i think the front one is ported and the rear is manifold [constant]
 
Demon Carbs are Excellent & easy to install & tune. But like anything else, if someone's messed w/ it before you, it's hard to tell what's been done. I love my road Demon because it's straightforward & wreaks of quality. The only real issue I (might) have, is MPG. But that's most likely due to the bigger cam in my car, probably not the carb so much.

If you ever have questions about your Demon, the guys @ Barry Grant are very responsive on their tech Support line (whose number I don't have on me).

I'm currently looking to buy another carb & will definitely make a Demon the choice (unless I get something else for free).
 
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