Demon carbs any good?

[kcsteck]

I bough a used demon carb on ebay. a 750 super demon carb. on trAILER BOAT SEEMED LIKE IT RAN OK TILL I PUT IN WATER TO TRY IT. It feels like some one was pourin water down carb from low speed all the way to floored. put buddies Holley 850 on it and it ran great? took Demon all apart and power valve was good,carb was real dirty so I cleaned it real good and put all back together.Havin buddy try on his boat to see what happens. Anyone got any ideas or tell me if Im waistin my time with Demon or not.
Thanks,
Casey

[beerjet]

I bough a used demon carb on ebay. a 750 super demon carb. on trAILER BOAT SEEMED LIKE IT RAN OK TILL I PUT IN WATER TO TRY IT. It feels like some one was pourin water down carb from low speed all the way to floored. put buddies Holley 850 on it and it ran great? took Demon all apart and power valve was good,carb was real dirty so I cleaned it real good and put all back together.Havin buddy try on his boat to see what happens. Anyone got any ideas or tell me if Im waistin my time with Demon or not.
Thanks,
Casey
I bought a mighty demon new and had nothing but issues with it . I luckily had the literature that comes with it and followed it closely and now I'm completely impressed . It runs lean but it really cooks !
-beerjet-

[xs ultra]

I have a 750 speed demon marine ,runs bitchin

[Duane HTP]

I've not had good luck with them. We run the 720hp/572 chevy crate motors on the dyno before we put them in and that King Demon leaves some cylinders rich and some scary lean. Fuel mixtures are all over the place. We put on the Gary Williams carb and it straghtens right up and usually pickes them up 18-20 HP. We have found, however, that if you put a Super Sucker http://www.highvelocityheads.com/ss.htm
under them, it helps straighten up the mixtures cylinder to cylinder a great deal and also makes more HP. They are just another give me your money box/ship carburetor with a little shiney on them as far as I'm concerned.

[Taylorman]

Duane, did you change the carb on the motor?

[Sleek-Jet]

My experience has been they take a little more tunning than a comparable Holley, but once you get it set up, they work fantastic.
Spend a little while tunning on the water, pay special attention to the float level, the fuel should be at the bottom of the site glass (and definitely no more a 1/3 of the way up from the bottom), not half-way up. Find out what jet's you are running, might be a simple matter of the thing is set up wrong for your engine.
Just my .02....

[olbiezer]

duane......lets face it ....... any gary williams carb will be right and flow perfect. if its not right gary dont ship! aways found it was worth every penny to have gary rework a carb lol

[kcsteck]

my jets were 76 primary and 83 secondary . Speed demon 750 twin squirter carb.

[Sleek-Jet]

my jets were 76 primary and 83 secondary . Speed demon 750 twin squirter carb.
According to BG's website, those are the jet's that it came with from the factory.
The peeps here that have all this down to a science will need a little more info on your set-up and what exactly is going on.

[kcsteck]

my set up is a 76 tahiti jet boat 455 olds bored 30 over comp cams cam 280H just under 500 lift,Single 4 barrel tunnel ram, Super demon 750 carb all stock settings,Headers,Mallory unilite distributor. under light or hard axcceleration it is stumbling the whole time.Like some one is pouring water down carb? Maybe dumpin to much fuel?someone said check float level,so will check that next.I put buddies 850 holley double pumper carb on it at the lake and it went like a bat out of hell put mine on wont get out of its own way. misin real bad!I took carb all a part and it was prety dirty inside so I cleaned the hell out of it.checked power valve looked good so put back together and gave to same buddy to try on his boat to see if it still does it since he was going to lake today. well see? dont think it was timing as it ran great with buddies carb. any help apreciated. I paid quite a bit for this carb and am about to throw it to the bottom of the lake.
Casey :cry:

[SmokinLowriderSS]

Is there any black smoke when it's missing? If so it's rich.
Pull a couple plugs (or all of em) and see what they look like after running on it a while.
Find out what size jets are in it as well.
IMO, an 850 is pretty big and may be box-jetted too rich for your fairly mild 455. You're probably only using 650 CFM or less from that carb.
Good luck. From what I've heard on here, some folks are running demon's just fine. I'd expect any carb change to require adjustment for best running, something from e-bay with questionmarks all over it (previous owner(s)) may need a lot more.

[kcsteck]

no black smoke,plugs look good,I already posted jets sizes 76 and 83 stock as came from factory.guess you missed that. Anyone have any suggestions where to send carb to get dialed in or do I send to bottom of lake?waitin to heare from friend if he had same problems with my carb on his motor? still need to check float level.yes I agree 850 was to big but i just wanted to try it for diagnoasis what was wrong with my boat. Coil hepled a little Carb alot!bingo its the carb! although to big but now I know.
Casey

[kcsteck]

bump

[Pee Dub]

You guys can knock Demon carbs all you want, but I have been totally pleased with the two I have used. Both of them were new and selected according to Barry Grant suggestions(website). I set the float adjustment too high on the first one and after a call to their tech line, I set it like a Holley, at the bottom of the sight glass. Didn't make the same mistake on the second one, left it at the factory setting. On the other hand, every Holley I have owned took plenty of tinkering with to make them act decent, especially the ones that were pre-owned. Doesn't make any difference what brand it is, if someone has been messing with it and you don't know what they have done, you could be in for a long haul to get it back to where it should be unless you happen to be a REAL hot shot on carburetors.

[kcsteck]

sorry Meant Speed Demon..lol.. what were your symptoms when your float level was set to high. Would it run like crap and feel like it was drowning?
Casey

[kcsteck]

if I dont figure it out where should I send it for someone else to figure it out?
Casey

[Pee Dub]

sorry Meant Speed Demon..lol.. what were your symptoms when your float level was set to high. Would it run like crap and feel like it was drowning?
Casey
Yup, it was in a car and I couldn't even get it out of the driveway. Guess you all read this before I got the P.S. edited out after rereading all the posts. I just wish I had a Demon on my flatbottom but don't know for sure what cam is in it and that is the key to selecting the right model and I don't want to waste my money.

[Pee Dub]

I would call directly to Barry Grant and explain the problems to them. Sending it back to them would probably be money well spent. You have the single carb tunnel ram variable that just may be pretty tricky to overcome.

[SmokinLowriderSS]

I'd clean it again, and run LOTS of spray carb cleaner through every single passage, several times.
Last year, my flawless 700 Holley suddenly came down from a FWO run with a surging/stalling idle I couldn't correct. A cleaning made it better, but still not fixed. ANOTHER cleaning finally blew the particles of cruddom out of the idle circuitry and VOILA!, she was back to her old reliable solid self.
Maybe some crud has gotten into the air bleeds, or the paassages to the boosters, the jet wells, anyplace to block up the flow of the main power circuitry. I'd burn at least 2 more cans of cleaner on it, maybe 3,and not the "environmentally friendly citrus" crap either if you can find better. Some good old Brake parts cleaner is dandilly harsh, and an old toothbrush, some toothpicks, maybe even some threads of copper wire to poke arround with. Just don't get rough and alter holes.

[kcsteck]

buddy just reported to me that he tried carb on his boat , same thing stack fires out carb when he tried to start the boat, wont get out of its own way once boat finally fied up. tried to start and Boom flames out carb. once started wont go just stutter from light throttle to hard throttle . wont go at all. Ill try take it apart again and also check float levels first.
Casey

[beerjet]

I dont have the tech line number handy but you should call them and they will definatly get you squared away. I recently went through this not to long ago and mine has turned out real good. As "someone" here told me . "Dont give up, figure it out and you will learn alot in the proccess"
-beerjet-

[SmokinLowriderSS]

Here's the tech number according to the website: Phone: (706) 864-8544
Also e-mail: tech-sales@barrygrant.com

[kcsteck]

yeh thanks for the number. Ive been talkin to them the whole time. Turned out that float levels were way off. I set now a hair under half sight glass and it runs now and does not backfire. Need to take to lake and try. Sounds way better now as well. Only thing carb might be to big for me from what I hear. Demon Tech told me that even though the Holley 850 worked fine on my boat that a speed demon 750 flows more then a holley 850 and might be to big for my boat. Im like why in the hell would you call it a 750 then? It runs rich with the Demon,at least better then runnin lean.Might need to get rid of the 750 Speed Demon for a smaller Demon or a holley etc.
Casey

[SmokinLowriderSS]

Damn, THAT would be maddening. A 750 CFM-er should flow something close to 750 CFM, an 850 CFM-er should flow something close to 850 CFM, regardless of the brand they are. I wouldn't expect then to be spot-on but with in 2 to 5% (and 5% is 42 CFM on an 850 making it either an 808 or an 892).

[berk]

i trashed the edelbrock 600 on my 383 and got a demon 650. the tech line said i needed stock jets and power valve but after bolting on the carb i had a sputtery backfirin beast. died every time it hit a wake, awful. so i richened up the secondaries alot and also the power valve. ended up 4 or 5 power valves up from stock and now she runs fine! although she guzzles about 2 times the fuel as the over lean edelbrock did.......

[cave]

If I had it to do it again I would have bought a Holly 850. I have a 850 Speed Demon. I had to get new floats. When I turned sharp the carb would cut out in that turn. No good in a jet boat. I bought oval track racing bowls (Loper's recommended them) and it really worked. I also replaced the float needle with an Off road spring loaded needle for those rough water days. My carbs still cuts out on really rough days but I just deal with it.
I would definitely get a Holly 850 on my next go round. I also stripped the threads on the front bowl. Still trying to find a place to get a new front bowl bowl. Looks ghetto with the JB weld but heck it got me back to the docks and has held up well.
Look into the floats. The left & right side look to be thinner than the center. Kind of a subtle V shape. Good luck.

[kcsteck]

yeh I know, that what the tech at BG said a 750 speed demon flows more the a 850 Holley. Had I known that I would have got the 650 that flows more then the 750 Holley. Im pissed! Now im chasin my ass to get it to run good with the 750 Speed demon. I had a 600 Holley on it last year and it went lean sucked valves etc. Dont want to go there again.
Casey

[bp]

i've been running 2 850 ,mighty demons for 3 years (and 4 championships). had some issues for awhile, but finally got 'em figured out, and i wouldn't want to trade them for holleys. in fact, we installed 2 950 holleys for a race weekend a year ago, and it ran identically. but i still liked the demons better because of the bowl windows, bowl removal screws, tunability with the ifr's and bleeds, and they look cool :cool:

[kcsteck]

THANK GOD . Got it figured out!!!!! Ran great today except for water leak and oil leak but Demon figured out finally! Thanks for telling me not to give up guys.
Casey

[kcsteck]

heres picture of my boat if someone can put in for me please.
Casey

[beerjet]

http://www.***boat.com/forums/attachment.php?attachmentid=13506

[DEL51]

heres picture of my boat if someone can put in for me please.
Casey
That boat looks like perfection. What a good lookin deal you have.

[49er]

They suck on blown motors .I had a friend that rattled the bearings out of two motors because he could'nt get them rich enough to work right
He sold them and bought two 1150 dominators and the boat felt like it picked up 150hp and about 12mph on the gps (NO BULL SHIT)

[kcsteck]

thanks Del51 for the compliment! I have all my heart and sole in that Beotch!
Casey :cool: