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I'm beginning to hate Demon

1K views 17 replies 9 participants last post by  OldTech 
#1 ·
Now all a sudden the front float will adjust to the point of running the engine out of gas or if I adjust it even a little it over flows into the carb. I pulled it out and tested it out in a pan of water and it floats just fine. I'm not going to talk about catching the garage on fire today. To much gas.
 
#3 ·
I have ran into issues before to where everything was fine but for some reason after I changed my floats I kept having problems where the front float would want to stick here and there and I kept adjusting it over and over again and had several times it was spewing gas and the worst time and I am glad I found it was something sounded funny and it turned out I had tapped on the adjuster screw so many times that it somehow got loose and I had fuel spraying everywhere and could have caught on fire and I was on my way to work and it was dark out and I heard this rushing sound and that was it.

What my issues turned out to be was the float hinge itself was bent a little on the tabs but you could not see it and it would not ride the roll pin smoothly and thus would hang up once in a while and the float would not go up and down like it was supposed to. I took it out and bent the tabs to where the float would go up and down smoothly and not hang up any more and my problem was solved. Yours might be fuel pressure related or I have came across bad needle and seats out of the box that was brand new but would not work right and never seal and I changed it out to another new one and it was fine. Also a thing to check is to make sure the rubber o ring is not loose on the needle and seat or it will allow fuel to leak by as well and not seal at all and make sure to put a tiny bit of vaseline on it before you stick it in you don't damage it.
 
#6 ·
Not sure what hat Demon means but if there's problems with Demon products know Barry Grant went down back when because of selling underdeveloped stuff to people who believed in the name and refusing to back it up. All BG/Demon parts on my cars, long since replaced at my cost.
 
#11 ·
That's not AFB based, that is based on the Carter ThermoQuad....just cleaned up a little.

The Edelbrock Performer carb line is based on the Carter AFB(Aluminum Four Barrel) for most of it's offerings, with the newest additions are based off the Carter AVS(Air Valve Secondary) series, I believe Edelbrock calls them Thunder Series AVS.
 
#14 ·
there are also private label summit M8600 carbs... these are actually holley 2110 and 2111 models.. but they are derived from the Autolite 4100 carbs.. with a holley style holley style secondary diaphragm..

these use standard holley main jets and tune just like them.. but as an additional feature.. the primary booster assembly comes out for easy changes to the Idle feed restriction and the accelerator pump shooter restrictions..

https://www.summitracing.com/parts/sum-m08600vs/overview/

https://www.summitracing.com/parts/sum-m08041/overview/
read the instructions linked below.... except for the location the theory is for all carbs..

https://static.summitracing.com/global/images/instructions/sum-m08040-41.pdf

whats old is new again..
 
#15 ·
If you want to get a regular holley style carb in place of the street demon that summit carb would be the best bang for the buck if you want to keep it similar with the two piece design which allows you to take the top off and not have to take the carb off the intake but if you looking to buy a regular traditional style holley carb I recommend a quick 600 or 750 street slayer carb as they have the options to change everything out from air bleeds to idle feed restrictors and power valve restrictors and allows jets in the rear as well as the metering plate they have in it has screw in idle feed restrictors and takes jets so you can jet up and down and for just a little over $300 is the best price and option available for not having to pay $300 for a new carb and then spend more to get a secondary metering block and then doing your own customizing work to allow the changing of the idle feed restrictors etc. If it was me I would spring for the quick fuel slayer carb as they are pretty nice carbs for the price compared to a similar holley brand. Second would be the summit one.
 
#17 ·
It depends on the tuner as well as the vehicle itself along with the build and there foot that can make all the difference on gaining fuel mileage. I always believed the myth that the double pumper would use more gas then a vacuum secondary and yes it does if you keep kicking in the secondary side of things but just cruising and a few romps here and there it can do exactly the same. I have cracked 20 mpg on both my holley 600 vacuum secondary and 650 double pumper with changing idle feed restrictors and also basic jetting. The summit carb does have one advantage over the other holley style carbs as I do believe you can change out the boosters and there would be a true way of gaining over 2 to 3 mpg or even more depending on the build as booster design can have a great effect on things.

I will have to do some research on them summit carbs and get in a little deeper and see just how they did get the extra mileage. I would get one of those is fuel mileage is the main concern and you want every ounce you can get and such I bet they would do just as good as an edelbrock afb style carb. I don't know too much about the thermoquad style but have seen photos and stuff and know the street demon is just an update of that carb but I have read mixed reviews on them though. I like traditional style holley carbs first over anything else since its easy to get parts and really easy to tune each circuit. I did not know on the summit ones you could change out the idle feed restrictors and that can make a big difference on fuel mileage as well by changing them out to different sizes.
 
#18 ·
The easiest carb to radically change the tune that I ever worked with is Zenith carburetors. It's a shame that most of the carbs they make are single throat carbs. They do make some 2 and 3 throat carbs for the import market.
I worked with carbs for industrial engines and the single barrel Zenith, even back in the early 70's had removable jets for idle and high speed air bleeds, idle and main jets and adjustable power jets. I adapted one to my 62 Falcon to see what kind of fuel mileage I could get. On a 550 mile trip I got 41 mpg. There was a cost for that kind of mileage - it had almost no power. I ended up putting a different kind of tune on it and setting the governor to 70 mph as a poor mans cruise control. I had full power right up to 70 mph and then it would cruise (with my foot on the floor). When it came to a hill the power came back and it would climb the hill at 70 mph.
The Falcon had a 200 inch engine swapped in and a C4 three speed transmission out of a E-150 extended van. I just changed the bolt-on bell housing and converter ti match the small six and away I went. I didn't even have to change the driveline because the C4 and Ford-O-Matic two speed were the same length. I converted and old three speed manual shifter to control the C4 and it was a fun car. That C4 was one of the test beds we used to make changes to for performance. We made a lot of mistakes but we ended up with a really strong performer that was as at home behind that little six as was behind a 600 hp blown 351 Cleveland. I have two almost identical in my two 302 powered 73 Mavericks. (daily drivers)
 
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