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View Full Version : Might Demon, Idle-eze, Long Duration Cam



Mean 69
07-24-2005, 09:30 AM
I am looking to replace the vac secondary carb on my 383, solid roller, with a 252 degree at .050 cam. Car makes about 10" of vacuum at 1k RPM idle.

I am always skeptical about what I read, but Demon seems to be happy that their Mighty Demon carbs are well suited to longer duration, more serious setup cars.

I don't need a choke, all I want is for the car to run well and not have to fuss too much with it once it is dialed in. I really want to do FI, but it'd take a lot more effort to install and I just don't have the time.

Any specific experience appreciated.

Mark

yody
08-10-2005, 10:33 PM
I would skip the demon crap all together and put an 950HP carb on that motor, better yet contact Pro-systems and see what they say

Matt@RFR
08-11-2005, 07:36 AM
Two things Cody:

1) Look at the date of the original post. Now look at your calender.

2) Define "Demon crap" please.

yody
08-11-2005, 09:00 AM
so what? it was a few weeks ago, did he already buy a carb? Well I have read about 100+ posts about dificulties with demon carbs, and i have tried to tune a 625 road demon, after spending an hour on the phone, reading the manual 2-3 times and spending days on the carb and AFTER flushing out piles of metal flakes from machining, i finally got the carb running right, and it wasn't even all that spectacular. All the probs I had were also probs other people have had. Yes they can be made to work but they are so much trouble and are finicky. There are all these "special" tricks you have to do to get them working right. Just put on a good holley, takes about 10 minutes to tune it right and you are good to go, well they arent shiny aluminum.

Matt@RFR
08-11-2005, 09:42 AM
Yes, Mark did buy the carburetor that he mentioned above allready...and is quite happy with it. More so when I get my hands on it. :)

Demons are extremely touchy...which, personally, is what I look for. Tiny adjustments make a huge difference, as opposed to a Holley where a 1/2 turn on any adjustment is required to see any change. (Not really, but you see my point)

My opinion is that the horror stories you hear are from people that either don't understand how to tune a carburetor, or are not willing to spend the time with it. It's extremely easy to get lost with them...especially with the models that have screw-in air bleeds.

Yeah, Holleys can be made to run ok, but a good carburetor on the same motor can run stellar.

The only way I'd run a Holley on anything with more than 240º @ .050" duration is if a profesional shop built it for that specific motor. Not to be a Richard, but I don't think you'll understand that until you actually pay the $800-$1200 for one, and see how a well tuned carburetor can run. Until then, you don't have a concept of a good carburetor.

And as a side note, a 950 is WAY too much for Mark's 383.

Matt@RFR
08-11-2005, 09:45 AM
There are all these "special" tricks you have to do to get them working right.

Almost forgot. Those "special tricks" are actually industry standards for making carburetors run well. Visit any good dyno facility or carburetor builder and you'll see them doing the same things that are in the Demon book, and more.

yody
08-11-2005, 10:23 AM
Actually, a 950HP is only flowing 830CFM it combines and 750 main body with an 850 baseplate making for excellent throttle response. i have one one my 454 with a [email protected] duration cam, it is probably a tad small for my combo but it works excellent, but it is box stock right now. It definetly needs some adjustments, but i prefer to do it on the rear wheel dyno as it has a wide band 02 and i can see the horsepower changes, next best thing would the track. Also a custom build carb does NOT cost $1200. You can get one for about $800. Also for some reason Demon underates all their carbs, so a 750 actually is a 800. That is straight from the horses mouth, and what about me and others getting carbs full of metal shavings?? That too is documented. My holley has adjusttable idle bleeds and I haven't gotten lost tuning it? Why should it be different on a demon? Why does Demon need special tech guys who surf the internet and have to post on boards to clarify things, and help people with their problematic carburetors, that is probably a good thing that they do that, but I have never seen so many complaints and problems, after drilling out restriction holes, cleaning out metal shavings, cleaing out needle and seats, spending hours with a vacuum guage, changing squirters/jets and etc did i finally get the road demon to run right, I hate edelbrock carbs and he could of just put a stupid edelbrock on it and not adjusted anything and it would of run exaclty the same for a third of the price.

yody
08-11-2005, 10:47 AM
but i should say that i don't think they are pieces of junk, just that I prefer Holleys, and they have been proven to be great perfomers, that don't need 100% tons of work. If tinkering with carbs is your thing, then a demon is just right up your alley
BTW my engine only makes 7" of vacuum and idles great!

Matt@RFR
08-11-2005, 10:51 AM
a 950HP is only flowing 830CFM it combines and 750 main body with an 850 baseplate making for excellent throttle response.
Sounds nice. I wasn't aware of that.


Also a custom build carb does NOT cost $1200.
They can.


You can get one for about $800.
I'm pretty sure that's what I said.


and what about me and others getting carbs full of metal shavings?? That too is documented.
That does suck. It's the first I've heard of it, but I don't disbelieve you. So, you don't take them apart first thing?


My holley has adjusttable idle bleeds and I haven't gotten lost tuning it?
Good! A lot of people do get lost with that stuff. Screw-in air bleeds are nice, aren't they?


I have never seen so many complaints and problems (snip)
Again, I think you're seeing way too many people that expect a carburetor to be a bolt-on part. And once they get into tuning it, they realise that they don't have the knowledge to do it, so they get pissed and bitch.

I do think that Demon (Barry Grant) should have a disclaimer to that end.


I hate edelbrock carbs and he could of just put a stupid edelbrock on it and not adjusted anything and it would of run exaclty the same for a third of the price.
There is no way in hell that would ever happen. Again, I don't think you've ever had the pleasure of dealing with a truly good carburetor, and I think your standards (as set by sub par carburetors) are getting in the way of your common sense.

I have no problem with guys not willing to spend the time to make a carburetor run near perfectly, but for christ sake don't try to do that and then bitch about the carburetor when it's clearly not the reason the motor doesn't run well. (Not directed at you, Cody. Just a general observation)

Matt@RFR
08-11-2005, 10:53 AM
If tinkering with carbs is your thing, then a demon is just right up your alley

Amen brother. :)

kman67rsss
08-11-2005, 01:12 PM
i think a lot of people expect that a carb is a bolt on part. throw it on, play with the idle screws, and go. i was one of them. this was my 1st engine build and i bought what i had read was good, and what my friends had run and liked. i had no idea there were unlimited adjustments on the demons, and i had no clue how to utilize any of them when i started. now that i have been playing with it for a few miles its starting to come around. i still dont know the 1st thing about adjusting a carb well but with the help of people like matt i am surviving and making leaps and bounds in progress. i think too many people lack the patience to adjust a carb well and therefore complaign about how its a POS

formula
08-14-2005, 08:39 AM
i concur, demons are highly sensitive carbs and i wish barry grant would bring that more to light. i bought my speed demon pretty much before i knew a dang thing about carbs, and i will admit i tried to adjust it like a holley (and even to holley specs in some places, like float level :doh: ) and for a while it ran like crapolah. however, now that i think that i've got it figured out, she runs smooth, idles at 500 rpm solidly ( i have come to the conclusion that my cam has no lobes at all ) and is all around a sweet setup.

i feel their downfall is also their advantage: they are very very sensitive to changes in atmospheric conditions and to tuning inputs, thus requiring a fair amount of fiddling fairly often. at the same time, it's possible to optimize them to every condition much more precisely.

the only thing i cannot stand about them is those piddly little float level adjuster gaskets on top of each bowl, that fall apart every time you try to adjust the float. those things shred just about instantly when you turn the float level screw.