What is wrong with my Speed Demon Carb?

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Purple Stallion

New Member

Jul 15, 2004

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May 10, 2005

#1

• May 10, 2005

• #1

Hello all. I have a 1969 Mach One with 377 Stroked Windsor engine. I purchased a Speed Demon 650 Carburetor with Vacuum Secondaries (1282010VE) from Summit Racing Equipment this past April. Today my father started up the car; he pumped it once and started it up and wouldn't turn over and then it started and black smoke came from the tailpipe and and missing like crazy and my father gunned it several(eight) times and no success. We shut off the engine, and found out that gas was all over the intake manifold and cleaned it up right away. It spewed out from the front cone shaped figure located just in front of the choke tower. I did a search and there was nothing that pertained to how to inspect for flashing. How do I go about doing this? If, flashing is not the culprit please let me know what else might cause the problem. Thank you.

 

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D.Hearne

New Member

Sep 29, 2000

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south louisiana

May 10, 2005

#2

• May 10, 2005

• #2

Sounds like your float's stuck, either from being improperly adjusted or you have too much fuel pressure.

 

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streetgrande69

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Nov 2, 2002

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Splendora, Tx

May 10, 2005

#3

• May 10, 2005

• #3

i second that motion. whats the reading on the float sight window. should be at the center line next to the window.

 

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Purple Stallion

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Jul 15, 2004

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May 11, 2005

#4

• May 11, 2005

• #4

Thanks for responding. Tomorrow, I am thinking of taking out the nut on the front bowl all the way out to see if there is flashing inside and reinstall it againg and lower the gas level because it is way past the top hash mark and the rear bowl reading is below the low mark. So, should I leave the front bowl nut alone and lower the float? Do you want me to raise the rear float to the center mark? Oh, do I have to flip down the gas cap to reduce gas pressure or does it matter? The last time I read the fuel pressure reading was five days prior to this catastrophe and it was close to 9 psi. Should this be 6 psi?

 

84convertablegt

New Member

Nov 6, 2004

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Columbus, OH

May 11, 2005

#5

• May 11, 2005

• #5

yeah, 9 psi is a little high. 5-7 is great. it is a speed demon, and they are known for having some issues new and it might need dissasembled and cleaned out and then put back together. id try to get the fp right and then adjust your floats so they are both right at the bottom of the site window. then see what happens. that is of course if you can get the car running long enough to do this. i suspect your fp is causing alot of these problems though

 

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Purple Stallion

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Jul 15, 2004

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May 12, 2005

#6

• May 12, 2005

• #6

carb update

Hey. I called Demon directly this morning and told them what happened and seemed to be of no help. I would think that there wouldn't be any flashing from inside the carburetor. They seem to be shifting the responsibility to the customer to correct their manufacturing defects from their CNC machining. Have any of you had the same problems with Demon Carbs where there is flashing inside? If so, what did you guys do to get rid of the flashing, I heard that Gunk is not a good product because it destroys aluminum. What other parts solvents are out there that won't hurt the aluminum? Right now, that's where it stands. Oh, I forgot to mention that I changed the fuel filter element on my Mallory Comp 140 fuel pump that is in between the fuel tank and pump. Do any of you think I should run an inline fuel filter between the fuel pressure regulator and the carburetor for added insurance? It is an aftermarket fuel tank from American Designers that is five years old. Could there be grit inside this tank already?

 

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nds03

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Jul 21, 2004

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May 12, 2005

#7

• May 12, 2005

• #7

i dont know what you mean by flashing. i think you should take your carb apart, clean out extra material from cnc machine and it sounds like you need a new float valve or its improperly adjusted. its pretty straight forward. if you dont know how to set the float, than its probobly about time to learn. your carb should have come with directions

 

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D.Hearne

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Sep 29, 2000

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south louisiana

May 12, 2005

#8

• May 12, 2005

• #8

I think that Demon carbs was correct in tellling you that they're not to blame for your problems. From what all you've posted, you sound like you simply don't understand carbs. Sorry to be blunt, but the facts are the facts. You've got a fuel pump that's 4 times too big and have nearly double the pressure that the carb needs and have obviously set the floats incorrectly, plus you're asking about filters shows you need to learn more about how a carb works. reduce the fuel pressure down to about 4-5 lbs, install as many filters as you want ( I run three between the tank and the 3 Holley 2 bbls on my 331 in my Ranger) then set the floats, til the fuel level is just barely up to the sight glass screws and your problems will dissappear, if they don't then remove the fuel bowls and inspect them for damage or any trash that may be there and also inspect the needle-seat assemblys for sticking.

 

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1965pony

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Apr 17, 2005

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Nor Cal

May 12, 2005

#9

• May 12, 2005

• #9

carb

I agree, your just having tuning issues. Im assuming that this its first run? Alot of people assume that since a carb is new it will go on and run perfect out of the box. Might be true sometimes (if your lucky) but lots can happen in shipping. I've run carbs with 9 PSI with out issues but you should lower it with a regulator. Should run for now.
Try to lower the bowl with the high float level. If you can't, remove the needle seat and inspect it for debris as D.Hearne stated earlier. Please be carefull about fuel building up on the intake. . Do your best to keep it dry. Back it out of the garage too. That distributor is real close to that carb and your plugs are fuel fowled. Scenario for back fire disaster. G-L Vince

 

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Purple Stallion

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Jul 15, 2004

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May 12, 2005

#10

• May 12, 2005

• #10

carb update

Ok, I should have saild metal shaving inside the carb-my error. I would have to disagree with D Hearne and 1965pony in that the customer has to be responsible for correcting a defect a company has put into their product. That means Demon can get away with poor quality control and get away with it and make the customer pay for unnecessary expenses. So I guess big business in control. Ok, D Hearne, I don't know about carburetors that is why I came on this forum to get information. So what are the purposes for these forums then?

 

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D.Hearne

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Sep 29, 2000

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south louisiana

May 12, 2005

#11

• May 12, 2005

• #11

Purple Stallion said:

Ok, I should have saild metal shaving inside the carb-my error. I would have to disagree with D Hearne and 1965pony in that the customer has to be responsible for correcting a defect a company has put into their product. That means Demon can get away with poor quality control and get away with it and make the customer pay for unnecessary expenses. So I guess big business in control. Ok, D Hearne, I don't know about carburetors that is why I came on this forum to get information. So what are the purposes for these forums then?

Click to expand...

You STILL don't get it do you? ----1. The fuel pump YOU installed is 4 times too large.(this is carbs 101 here, not EFI, you don't need a humongous fuel pump to keep any carb supplied with fuel, I run a 30 gal/hr pump in my Ranger, and even with full power passes at the strip, it's never failed to keep the three Holleys suplied with fuel) ----2. YOU set the fuel pressure twice as high as the carb needs. 3. YOU have failed to set the floats incorrectly. ------------- Now, HOW does that make YOUR tuning problems, Demon Carbs fault? As far as I've read, someone else, said you MIGHT have flashing in the fuel bowls that MIGHT cause your problems, but until you address the other problems I listed above, IF you DID have flashing and you did eliminate it , you would STILL have the same flooding problems. Only then could you possibly blame Demon Carbs for your problem.

 

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1965pony

New Member

Apr 17, 2005

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Nor Cal

May 13, 2005

#12

• May 13, 2005

• #12

whoa

now now guys, lets not get our saddle straps twisted here. Remember we are trying to help you.
You stated flashing and I have the understanding that flashing is cast flake that is still connected to the main cast. You already appologized about that so lets move on.
Ok now if there is metal floating around in the carb bowls then you must find the source of the metal. Is it from assembly or installation? If metal is in the bowls then check your filters. Try to find the facts before you cry foul. Get the car to a shop have them make an inspection...if it falls in Demons fault then send them the bill with recommendations for correction. good luck

btw where are you? Vince

 

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Purple Stallion

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Jul 15, 2004

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May 16, 2005

#13

• May 16, 2005

• #13

Carb had aluminum shavings inside.

I took it to a shop and found out it had aluminum shavings inside the carb and were traced as far back to the vacuum secondaries. I picked up the carburetor and installed on the car. I also had the tech inspect the fuel filter and turned out clean. So debris from the fuel tank was not the issue. By the way I should have mentioned I was running an electric Mallory Comp 140 series fuel pump with regulator. I started up the car today, I primed the carb by bumping the ignition to the on position until the fuel reached the halfway mark and started up the car. I fired up the car with no problems. It has a high idle but no missing or smoke that I could see. I'll take to the shop to have it dialed in.