Engine is a stock long block 5.9 out of a 94 ram. BUT I installed a Hughes Engines Whiplash cam for some thumpity thump.


Swapped everything over to a carb setup running an Eddy RPM airgap. Current carb is a 750cfm Street Demon. It has to just be waaaaay to much carb. It is so rich. You can smell the fuel at idle and it bogs down and is a dog off the line if I don't clear it out. I have tried detuning it, springs the whole nine. Just cant get it to not idle so rich.

I would either like to run an Eddy 650cfm (I do not know which series would be best for the street) and Eddys seem to always run well out of the box with very minor tuning or give the Street Demon 625CFM a go.

Anybody have any opinions?

Larger carburetor doesn't add more fuel, it adds more air.

vacuum is probably very low with all the overlap that cam brings to the table. recalibrate the metering system before buying another carb. chances are another carb will do the same thing.

The Street Demon has been my go-to street carb series for several years now. But a rough idle would be better served with a 4 corner carb like a 4150. IF a guy can actually tune the idle and transition circuits.

When the cam is configured to where the idle is rough, it will pretty much ALWAYS burn your eyes at idle. The reason that the idle bumps is because both valves are open at the same time at low engine speed. The result of that is that some compression is pushed into the intake stopping the flow causing fuel to fall out of the airstream. So some cylinders get too much air while others get too much fuel. That causes the distinctive lope at idle and the exhaust stink. They go hand in hand.

But, with proper tuning of the timing and the carb, it can be reduced.

What does your spark curve look like?

The Hughes whiplash roller isn't that big of a cam, smaller than my 220/220 @.050 with a 108° LSA, installed at 106° centerline, it just has more lift, mine is only .470. I'm using a Holley style FST 650 vacuum sec carb on mine. It has 4 corner idle but I don't think it needs it, the idle screws are maybe a 1/4 turn. I had to go up 2 or 3 jet sizes in the front and the same on the sec side I think. Had to up the squirter from a 32 to a 38. I had to run it really dirty before I got the distributor and timing right. Right now I have 12° at idle, 36° full advance all in by 1700 and no vacuum advance. Runs really good now and the idle is cleaner. Without any manifold heat the magnum setup needs to run a little richer than an LA would have to with manifold heat. First step is get the timing and advance curve right then worry about the carb.

That's really good advice.

Too bad Jonesy has me on ignore and will never know that I agreed with him and complimented his advice.

The 440 TQ (big primary’s) but then again either one will wok fine.

i like those big T-Quads as well.

You should either learn how to fix that carb or send it to Thumper Dart
i have not worked on a Street Demon so I have no idea on how to fix your carb, big cams not degree in can raise havoc with the carb signals making them run poorly.
Is that carb mechanical linkage with four corner idle mixtures or vacuum operated secondary with two idle mixture screws?
If mechanical linkage with 4 corners idle circuits, try speeding up the idle speed a little on the rear throttle plates and lean down all four idle mixture screws a little at a time by turning each one in slowly until the motor RPM starts to slow down the RPM. Once that is done then slow the idle rpm down by closing the front two barrel linkage until it will idles smoothly and smells better

Sorry for the late reply everyone, I have not been on all weekend. I'm sneaky I check the boards at work

The carb has Two idle mixture screws in the front and is a Vacuum secondary. I have messed with the floats and the springs in the carb with tech support suggestions. I will definitely give it some more tuning before dropping more money on different carburetor.

Last winter when I was trying to dial it in I was using a Vacuum gauge to help. I will have to play with the timing and see if I can dial it in any better than I did. Or maybe something with the distributor. It is an HEI style one wire hookup with vacuum advance and ignition pack build into it.