New Holley 625 Street Demon Problem.

Thought I had my 71 Cuda all ready to drive to the Nationals but..... car all of a sudden won't idle when I tried to go to work in it this morning. I just put on a new Demon 625 a couple of months ago. Have driven around local probably 100 miles or so since. I've verified the obvious such as bad fuel. I did just fill the car up but it will not run any better out of a fresh can of gas.

Anybody run into this issue with their Demon? Getting ready to pull it off and put my old seepy thermoquad back on. Car ran great with that for years. Just couldn't stop the slight weeping from the upper gasket so I dropped some bucks for a new one. Any ideas would be greatly appreciated?

Thanks.

Have you checked for simple things like vacuum leaks? Maybe it's not the carb at all.

I bought one when I was restoring my 69,, It was junk from day one.. Get rid of it!!

look for a piece of dirt in the idle jet.

Can you see the float levels on that carb? Can you verify that the needles/seats are not hung up with debris?

I remember someone here posting they do not like the 10%ethenol gas, eat the accel pump transfer tube up and they sent it back.

might have a look at that.

No vacuum leaks. I would bet my Thermoquad works just fine when I put it on.

When I installed this carb I put on new lines and a new filter. I also went the extra mile to cut my old filter up just to make sure I didn't have any rust particles coming from the gas tank. The old filter was pretty clean and no rusty particles. This Demon just appears to have bitten the dust pretty quickly.

I have a couple 71 t-quads but no plastic bowls laying around. Try sanding the top of the bowl on a sheet of 220 grit sand paper to get it flat. The paper should obviously be on a flat surface.

get a can of brake kleen with a thin red straw & shoot a 3 second blast into each idle screw mixture port. first count the # of turns to lightly seated before you remove em so you can easily return the screws to their original position(s). then get a high flow 10 micron filter in line right before the carb inlet to ward off a repeat

I'll give that a shot before I pull that Demon off. I did just fill the tank up to get ready for the Nationals. Maybe I rustled up some junk in the tank or pumped some in from the station and it got past the filter.

the idle circuits have the smallest passages in the whole carb & it only takes one minute piece of debris in the wrong place to make it act up & speaking of the gas stns I've seen (& am amazed) at the amount of crap that gets past their "filters". Holler how things turn out

Well the Cuda is now running good. Why???? Not exactly sure. After work I bought another fuel filter that was 20 micron. I removed my old filter and cut that in half. It showed no signs of any issues. No dirt nothing. Looked new. I went ahead and installed my new filter and tried cranking the car. At initial trials without starting it backfired thru the carb once and rammed the horn plate closed on the Demon. I opened that back up and with a few cranks started the car. Let it warm and reset the air fuel mixture screws. It now runs great.

I would like to think that it just had some dirt in the carb, from were I don't know, and running the carb dry of fuel then repriming freed the dirt plug. or....... I have a minor vacuum leak and it is now sealed, for now. I did tighten the carb mounting bolts a bit last night but saw no change at that time. Tightening when the car was at temp.

Drove the car for an hour or so. Runs like it should now.

Awesome news!

I'll bet the lean backfire did it. Happy motoring!

Looks like. I ended up putting my old Thermoquad on there anyhow to play around with. I'm gonna try to get that weeping at the upper seal issue fixed. I really like the old carb better than this Demon anyways. I wonder if I have the float settings a bit too high on this Thermoquad?