625cfm street demon

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Mike 340

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Hey everyone, I am new to this forum just wanted to know if anyone has tried the street demon 625cfm carb?
I just put one on my 340 and I have found that it seems lean. My engine is a 68 block with 71 J heads and tq intake with 71 340 exhaust manifolds and a comp cam 268xe . Any input or information would be great.
It's just a cruiser 5500 rpm . Already have the calibration kit.
 
Hey everyone, I am new to this forum just wanted to know if anyone has tried the street demon 625cfm carb?
I just put one on my 340 and I have found that it seems lean. My engine is a 68 block with 71 J heads and tq intake with 71 340 exhaust manifolds and a comp cam 268xe . Any input or information would be great.
It's just a cruiser 5500 rpm . Already have the calibration kit.
Mine is in a 67 dart gt 727 auto with 3:55 gears and MP performance ignition with the orange box. Car seems to be very responsive, but doesn't leave alot of wheel spin .
215 r 14 tires.
 
Mine is in a 67 dart gt 727 auto with 3:55 gears and MP performance ignition with the orange box. Car seems to be very responsive, but doesn't leave alot of wheel spin .
215 r 14 tires.
White spark plugs
 
94 octane. It's the best I can get. Most around here is 92. There is a airport that will sell me av gas but I don't think that I should.
 
How does it RUN? Does it pull good and want to keep pulling, or does it lay down at high RPM?

If all you are basing your opinion on is spark plug color, throw that out the window, because as already stated, you cannot read plugs on modern gas.
 
The "fatter "I jet it the harder it pulls and the better it idles. The plugs are starting to get a light tan color now. I think I am going the right direction.
 
Hey everyone, I am new to this forum just wanted to know if anyone has tried the street demon 625cfm carb?
I just put one on my 340 and I have found that it seems lean. My engine is a 68 block with 71 J heads and tq intake with 71 340 exhaust manifolds and a comp cam 268xe . Any input or information would be great.
It's just a cruiser 5500 rpm . Already have the calibration kit.


If it's like the Edelbrock it should have a step up rod chart. I would first find a back country road for doing the tuning. Start out with making a full throttle pass and while coming to a stop shut the motor off. Don't let the engine idle. Now pull a couple of plugs and see how they are burning. If they are looking a little white in color I would say you are a little lean. If that's the case go by the step up rod chart to see which rod you should use. You may get to the point based on the chart where you may have to change jets.

If your plugs look a medium to dark tan then you are in the ball park. If the plugs are black or even wet you are too rich

Of course everything else with the engine should be up to speed.
 
A little off topic but did you have to use the demon carb throttle stud or did the one from your previous carb work? I ordered same carb a couple of days ago but don't know if I need to order the stud also while I am waiting for delivery.
 
The "fatter "I jet it the harder it pulls and the better it idles. The plugs are starting to get a light tan color now. I think I am going the right direction.
A little off topic but did you have to use the demon carb throttle stud or did the one from your previous carb work? I ordered same carb a couple of days ago but don't know if I need to order the stud also while I am waiting for delivery.
Yes you need the throttle stud and you need to split the carb to put it on. I found out the hard way and had to take it back off the engine.
 


Check this video out, a Street Demon 625 carb on a Dart, it will show how to install the Chrysler linkage at 3:26 of the video
 
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