GRRR. My buddy is back!

[Anonymous]

I thought I had the problem of stalling worked out after I changed the carb adapter. Well, the only thing that solved was the stalling on left hand turns and it only solved it by switching the stalling to the right hand side. Well, on the bright side, the problem is definitly inside the carb because the stalling switched sides when I turned the carb 180 degrees. I e-mailed tech support for Demon carbs, no reply back yet..... e-mail sent on Friday.
Around 1000 rpms, while warming up after start, it will surge a couple hundred rpms and then go back down, then surge again, over and over. That along with the stalling on right hand turns, surging when cruising around 30mph even when warm, stumble under light acceleration while driving straight, and it seems that both the fuel mixture screws do jack squat to the engine when I screw them in (individually). I don't know. There are several troubleshooting steps for these problems, but they tell me to raise the float level, the other one says to lower it. I reset the butterflies with the engine idle speed screw (which seems odd because I have to just turn around and screw it back in to set the idle rpms), lowered the float level to the bottom of the sight gauge (it was half before) and turned out the mixture screws some more (Speeds up the engine a little when I turn them in). Hmm, I've also made sure that a good squirt comes out when I pump the throttle. I've even sat on the fender to make the car think it's in a right hand turn and pumped the throttle to see what happens (nothing). I'm beginning to HATE carburators, or at least Demon carbs.

 

[wsa111]

Which, carb do you have, the 350 or the 500??

Then we will go from there.

 

[Anonymous]

The 350. And... Still nothing from Demon techies.

 

[wsa111]

The Demon is just like a holley.

Replace the power valve with a 8.5. Try changing the main jets 2 sizes leaner, a holley would go from a 61 to a 59 jet.

Set the float to the lower part of the sight glass.

Now see if you can screw the idle screws in and the mixture will lean out, if not, you have a carburetor internal problem or metering plate leak at the gasket area??

All these demon & holley carbs are too rich from main jets to the idle jet.

This is a very technical area which involves metering block idle orifice changes & idle air bleed changes, but these can be addressed after you get the basics mastered.

 

[MustangSix]

On sideways carbs, you often have to add jet extensions to account for the fuel moving to one side of the carb on turns (I think I might have mentioned that before). It keeps the jet entry submerged. This is also a problem on road racing cars that have high G decelleration that uncovers the primary jets.

Holley has them available; not sure about Demon, but I suspect they may.

 

[66200i6]

I have always associated surging at low RPM and at low torque cruising to a lean condition. I have experienced this on several occasions when dialing in a 2100 on the FE’s.

I have also made my own Main Jet Stanchions. Just use brass or copper tube with an ID just large enough for a press fit over the jet. With the correct size screw driver you can even install and remove the jet after the stanchion is in place. If you don’t have the right size screw driver you can always install after the jet is in place.

The length needs to be below the height of the fuel level and should not interfere with the operation of the float.

Good luck, Ric.

 

[Anonymous]

Well, I noticed that there is some gasoline residue around the base of the carb (where the mount bolts are). I'm going on Leave Saturday so I thought I would try some simple things until I get back and if its not fixed now then I will try the power valve and main jets and possibly the extensions. I removed the carb and tightened up the screws next to the butterflies on the bottom. I assume that those tighten up the base to the rest of the carb, hopefully that stopped the leak, I did notice that some were tight and 3 others were just snug. I also turned out the idle mixture screws a little more and took it for a test drive. It still feels like it wants to stall on right hand turns but I couldn't make heads or tails of whether or not it is better. I stopped during the drive and turned the screws out another turn just to try it. Again I couldn't make heads or tails of it. I just know that it didn't get any worse. Last thing was taking it up a TINY hill that I take home from work. It used to surge noticable and I could hear the exhaust surging from the inside of the car. This trip however, I didn't notice any surging. I'm going to drive it to work tomorrow to see if it is officially better or not.

I forgot: While warming up the engine for this test drive, I didn't see any of the fluctuations that I noticed before. It used to jump from 1,000rpm to 1,200 rpm, back and forth. Today, nothing. I'm beginning to think that the leak was the problem.

 

[Anonymous]

I got a reply back from Demon techies:

" Running the carburetor in the orientation that you are, may actually require running the float levels even higher to get it to drive properly through corners.

Thank you,

Technical Support"

I raised the float level a bit more and tried to get it to stall out on turns but couldn't. It does seem better, but I do notice a small dead spot, I probably still need to raise it a bit more. Seems close to driveable. The mixture screws are backed out 4 turns.

 

[jamyers]

4 turns out seems like a lot, but if it's happy and your mileage is ok, sounds like you're there! 8)

 

[Anonymous]

I only had a day left before I left on Leave to mess with the stang. So I just messed with the carb a little to see what I could get it to do. Seemed to run good. I thought that 4 was a little much, I've also read some other posts on here about some people having theirs out like 3 turns.