Hello all. I have a pretty much stock 305 LG4 with a 650 speed demon. The carburetor has pretty much a pain from the beginning. I have taken it to 3 shops and played with it myself. The last shop I took it too pretty much fixed some of the problem. The carburetor has ran rich from day 1 rich to the point the car would spit gas through the tail but the car ran great but used hella lot of gas. The last shop I took it to changed the jets to 67primary 70-71 secondary and put a 25 he called it a squirter I think he was talking about accelerator pump discharge nozzle. A 31 nozzle came in this carburetor originally. The car still runs a little rich, sitting still at idle revving it, it will spit some black soot/gas out on the ground but in gear it's super lean. When I barely putting my foot on the gas it will pop and die out. Off idle I have to flutter the gas till it gets to about 1500rpms then it just acts normal. And while cruising if I easy on the gas the RPM’s drop to 0 car stutters then picks back up and goes. Anyone know what could be causing the problem? The jet size for my motor seems like its right but I think the nozzle is to small. Does any one have any recommendations on what to try as far as jets and nozzle? I am going to purchase that book “SA Design: How To Tune and Win With Demon Carburetion” and some different nozzles 28 and a 31 I already have a jet kit. Would this be the best way to go?

EDIT: Buying a new carburetor really is not a option right now and i plan on modding the engine later down the road. Vortec heads, XE262, Edelbrock RPM. Then way later a Wheeler 383 short block and different cam.

 

try installing a bigger accelerator pump cam. what is your timing set at?

 

I dont have a timing light, but its set to the CC-Qjets seting as far as timing I have to check the sticker under the hood when I go out tomarrow. I also go to sears tomarrow and buy a light to make sure but somone has to tell me how to use it cause I have never used one.

 

You're still using the computer controlled distributor? And 3 different shops didn't tell you that's a no-no?

 

did you change out that computer controlled distributor when you swapped to a non computer carb? if not, thats your issue...

 

no its a non cc distibutor but it set to what the sticker says(the CC-qjet sticker under hood) as far as timing goes.

 

I run 12* timing with a maximum of 36*. I run 66 jets on my primary and dont have a secondary. I put in a bigger squirter (not sure of the size). I had larger jets and smaller squirter and was running way too rich. I was dumping fuel at idle as well. The car runs a little lean except when I get on the throttle and then the bigger squirters kick in and supply the fuel. If you were running way too rich you need to check your oil. If it's black, you need to change it asap. That would mean you have fuel in the oil and you will ruin your cam. Hope some of what I said helped. It's late...LOL

 

The factory settings are moot now. The 3 shops should have known that as well. 8 to 12 degrees initial timing, at idle with the vacuum advance disconnected, is where you should start.

 

Ahh Demons!

Very sensitive carbs overall.Make sure you have the float levels set a lil below half way otherwise it will be rich at idle no matter what.Get the timing sorted out first as 5-7 said.Try at least 8 at idle.Demons like alot of initial to tip in nicely.I run 13 at idle (set with vacuum can disconnected) with my motor and full manifold vacuum.As far as the tip in stumble..what pump cam are you running?The stock pink?If so throw it out..not really but swap it for the holley blue cam #427.Go back to the stock 31 squirter and swap in the blue cam.Put it on the #1 hole.This will help the stumble.Trust me..I went through it with my Demon.

You can run all Holley cams,jets,squirters,etc on the Demon.Pick up the pump cam kit.Run the blue.The pink is just way too lasy on a street bound Demon.I highly recommend the book “SA Design: How To Tune and Win With Demon Carburetion”.I have it and it helped alot.

As far as being to rich at idle..sounds like fuel pressure or transistion slot.These are very important to a Demon.What is the fuel pressure at?The transition slot has to be correct otherwise the car will idle rich also.Mine was off and the car would stall every time I let off.Close the fronts down a little and crack the back throttle screw.Try to balance them out.You might wanna pull the carb off to set these correctly.Try these first few things and see how it reacts for ya...let us know?

 

K I got a light I shoot in behind the water pump right? And all I see is the timing tab with no numbers and a line kind of at the center of the timing tab. Also when I disconnect the vacuum can is the car running or do I disconnect then start it. I also called around trying to find a pump cam kit no luck yet found the 31 squirter though.

 

K I just picked up some 28 and 31 squiters to try I am going to have to order the pump cam kit form jegs or something, if someone has the kit# that be great if not I will find it. But I like to try to get the timing figured out I’m not sure what I am looking at or for?? I don’t see any numbers anywhere. Just ordered part 20-12 Accelerator Pump Cam Assortment and the SA Design Book.

 

there is a line in your harmonic balancer. can sometimes be hard to find. its indented in it. turn the motor over by hand until you find it then paint it white or any color you might have that will stand out. try to make the line as fine as possible. i use a paint pen or white-out liquid paper. you can disconnect the vacuum line at any time, just be sure to plug off the line so you dont have a vacuum leak. turn down your idle set screw that way the car will idle low, around 600-700 should be fine. your sheet metal timing pointer should have numbers stamped on it. just barely loosen the distributor hold down tab that way after you move it, it will stay in its place. hook up the 2 battery leads to your batt and the other "clamp" to the #1 spark plug wire. put your timing between 8-12 as mentioned before. test various timing settings by snapping the throttle, try to get the setting that has the snappiest throttle response. be very careful of the leads for the timing light. when your doing to many things at once, the cables will get caught up in a belt easily. hopefully this and the book will help you out.

 

Yes I found the line on the balancer that’s no problem but the timing tab it doesn’t appear to have numbers on them I guess I have to find something to get in there and wipe it off. but the timing tab on appears to have about 3 grooves 1 small on each side and a large on in the middle.

 

I read this with interest because I too have a 650 Speed Demon that's been a PITA since day one too!!

I've already tried most of what was mentioned already, same results...rich at idle - I mean burn your eyeballs rich. But revs quickly and runs strong off-idle and WOT. I checked:

.040 transfer slot clearance (6 times)

Initial timing at 20 degrees...(keep in mind I'm running a straight mech. advance distributor) - it won't run decent at anything less than 18. Presently running 73 prim. jets and 81 sec.

Float level - tried raising and lowering, doesn't seem to help.

I've almost worn out my 4 corner idle screws by adjusting them so much. I can turn them in till the engine runs lousy, and it still seems rich. It also has the "Idle eeze" feature....doesn't really effect it either.

Never tried changing squirter sizes, but that shouldn't have anything to do with it at idle right?

I'm not trying to shanghai zNucleaRz's post, but I see alot of simularities in our Demon problems. I've considered selling this thing and getting a Holley, even though Demon is SUPPOSED to be a better carb....

 

The bottom of the large slot on the timing tab is zero degrees (TDC). The first point towards the center of the engine is 4 degrees BTDC. Every bottom and point thereafter is another 2 degrees each.

Get a can of engine cleaner and spray down there. Let it soak for a few minutes, blast it off with a hose. Repeat as required.

 

Hey everyone I got my SA Design book its a very good book but some things differ from the book and Demon's website. Demon says my carburetor came with 31 squirters book says 28. But I bought both so really doesn’t matter. Now what’s the difference between squirters with nozzles and without? The book doesn’t show.

 

Don't take the book or website as gospel for what the carb came with.What did it actually come with?..should be a 31.Tube type squirters have little tubes sticking out of them and aim the accelerator pump fuel shot more towards the absolute center of the boosters.Non tube type don't ave tubes and seem to spray al over the booster as opposed to just in the center.Demons are supplied with non tube type.Always heard the tube type are better but I have no experience with them myself soI can't really say either way.Did you get the timing figured out and set?

 

You have the correct PV in it I assume?You may need to enlarge your idle air bleeds.

 

No I have not had time to play with it (timing) I have a long workweek this week. I Should beable to get to it saturday.

 

Got another question when I disconnect the distributor vacuum hose the car doesn’t change. Doesn’t this cause a vacuum leak shouldn’t it want to die out? It doesn’t do anything when I disconnect it.

 

Are you connecting it to a ported or full-time vacuum source?

 

The front port closest to the front of the car so yes I guess that’s the timed vacuum port. In my new book that’s what it says it is. Also on BG website the port I have it in says Ported or timed vacuum foradvance to occur with throttle opening.

 

There'll be no vacuum on that port then until the throttle is opened, so the idle won't change.

 

should I have the distributor in this port? The other port reads Direct manifold vacuum for diagnostics, accesories or for Disstributors that use manifold vacuum for timing advance.

 

You can use either port, depending on what you and your engine prefer.

 

Try it and see how the car runs...I run full manifold vaccum with my Demon.

 

I am going to go out and play with it some tomorrow. Got a couple more question though. When I go to full throttle off the line it feels like the car is slowly accelerating kind of like the secondary don’t kick in off the line at WOT like it’s more of a progressive feeling. Does this mean I should try different vacuum secondary springs? Or this is just probably cause I have a 145hp 305 with like a stock 1250 stall or something. But I know I cant spin the tires off the line and I can get the rear tires to break lose when the transmission shifts form 1-2 at 5500rpm. Now as far as the timing when the car is in park idling giving it gas the idle is snappy but in drive is when every thing goes wrong. Would this mean probably the last person who tuned the car did not do it with the car in Drive and someone pressing the brake pedal?

 

can anyone tell how to change the accerator pump cam? i know how to change the squirters but not the pump cam.

 

On the side of the throttle shaft there is a phillips head screw.Take it out and more than likely the pump cam will fall out..replace with new cam.

It is the small circled piece contained in the larger circle.

 

holding the cam as pictured i was told to indstall the cam in the number one whole witch is the number one hole?

 

k i got it i noticed a 1 and 2 actually on the cam. I changed the squirter to the 28 and the cam to the blue 427 it runs great!!! Only problem i had the pump arm got stuck on the back throttle cable stud when i was testing it the car reved to 7K . I had to relocate the trottle cable to the very top hole in the linkage but i had to use a screw and nut to attach it the throttle stud is to large for this hole. Thanks for everyones help. And also the timing is right its was at 10.

 

Bump the timing up to 12 as well.That will help even more.Just make sure you don't go over 36 total.

 

12 pending that it dosent ping because of bad gas. If you dont run High or mid-grade, or at the very least a gas additive, you might ping depending on the place your at. Not to be negative. I had an issue once with a station i could tell the gas was bad because of pinging. Didnt wanna retard the timing, so i went elsewere, gas was better and no ping.

Muirner

 

The problem persists!! It ran great that whole day. And over time it got worse and worse now I back to where I started. It’s gotten real bad lately. To the point if I floor it from a dead the car just turns off doesn’t even sputter for gas just shuts off. If I ease it in it backfires multiple times through the carburetor till about 1500 RPM’s then the car takes off like a rocket. But if the car is warmed up say 190 degrees the problem is less noticeable at low RPM’s I can ease on the gas with no backfire just a little shutters but if I step on it, it backfires. I tried turning up the idle some think it was to low and it made the problem worse! I could actually see flames coming out of the carburetor when I turned the idle up to about 750-800. Anyone have any other suggestion I can try? This carburetor is starting to get the best of me I think. I’m also wondering if it might be an ignition problem. Maybe I’m not getting enough spark till after 1500 RPM’s could this be possible? And if so would I see gas shoot up out of the carburetor when it backfires? Also could it just be that I jetted the carb down to far casue since the carb is a 650 and it was origonally built with 70 primary jets that it just doesnt like the 66's I have in it?

 

My car did the same thing. It was because after I set the timing I didn't tighten the distributor enough and it moved. Might be that if you tried changing your timing

 

I got few more question now when I start the car and give it gas say me giving it gas to about 2K to let it warm up the idle kind of jumps just enough to see the needle bob up and down. Once the car is warm you can’t see it doing it anymore but you can here a pop in the exhaust not backfire but a small pop and you can feel it in the floorboards?

 

wow.. glad i found this one.. I am having the same problem with my 4160 carb on my 305.... (had a long block that was good and had a 4160 carb and an edlbrock performer intake manifold) Anyhow.. same problem.. idles rich, but leans when on the road, and runs a bit rough.... anyone have any ideas.. I know i should have the timing set up to 8 (it's at 6 now), what other settings would you all recommend for the carb on that 305 engine?

 

I think I fixed it!!! I moved the vacuum advance from the progressive vacuum port the full vacuum port. Right when I switched the hose the idle increased and smoothed out. I drove it around the block seems like I don’t have any part throttle hesitation anymore. I also turned my primary screws in ½ and it seems to run good so I guess well see if it holds up this time.

 

Also when I installed the Holley blue cam I had to turn the nut that pushes down on the accelerator pump lever on the primaries is there a proper way to adjust that cause I left it a little loose.

 

Adjust it till there is no slack between the bolt head and acc pump arm.