Eddy 1405 tuning advice

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Tried heavier pink spring(to make it richer) and ran like dogshit, stalled etc. Anyone know if carter springs are/were same as Eddy?
Thanks
Steve
 
They're not exactly the same, but you can make them work. Have you tried the Carter in your picture? It's only a few minutes to see if the symptoms are the same with another carburetor. I think it's been mentioned on this thread, but Edelbrocks are running on the idle circuit at a higher cruise speed than you might think. I tune these with the help of a wideband (just to see the neighborhood I'm in), and in my experience, they're lean just at the top of "idle" cruise, which may be up to 60 mph with a tall enough gear. Past that, they're running on the mains, and then the rods/jets come into play. My experience is also that they're rich under full throttle, but that's better than the other way around. I generally will reduce the size of the primary idle air bleed on top of the primary venturi cluster by .003, and that often takes care of any minor surging. But if you have backfiring where there wasn't any before, something must have changed. As I said earlier, I'd be popping one of the other carbs on there to rule out any problems with the 1405.
 
Thanks for the info. Yeah the Carter in pic is one I want to try. It was on it before and ran fine. Use it as a diagnostic took so to speak lol. I also have 1406 that I've gone thru but I only ever had it on dq, so never setup for a single 4bl.
I went thru the Carter, last night. All looks good. Plus it's what the fsm specd for this.motor, and its 500 cfm.
The closest spring in size is the pink Eddy, which is 7".
I'm not sure if the Eddy springs are a direct match?
Thanks.
They're not exactly the same, but you can make them work. Have you tried the Carter in your picture? It's only a few minutes to see if the symptoms are the same with another carburetor. I think it's been mentioned on this thread, but Edelbrocks are running on the idle circuit at a higher cruise speed than you might think. I tune these with the help of a wideband (just to see the neighborhood I'm in), and in my experience, they're lean just at the top of "idle" cruise, which may be up to 60 mph with a tall enough gear. Past that, they're running on the mains, and then the rods/jets come into play. My experience is also that they're rich under full throttle, but that's better than the other way around. I generally will reduce the size of the primary idle air bleed on top of the primary venturi cluster by .003, and that often takes care of any minor surging. But if you have backfiring where there wasn't any before, something must have changed. As I said earlier, I'd be popping one of the other carbs on there to rule out any problems with the 1405.
 
Totally unscientific, but factory Carter springs are probably on the stiffer side (depending on the engine). I don't know for sure, but I'd guess they were closer to the 8" springs in the Eddy kit. I'm sure, however, that every engine had a specific spring. I don't think you'll feel a difference between a 7" and an 8" spring. You have to be pretty far into the pedal to get into the power circuit most of the time. Have you checked cruise vacuum on your combination? Even if you're idling at 14", your cruise vacuum may be higher than that.
 
I'll chk my notes to see what cruise vac was, but pretty sure it was mid teens. The Eddy yestersay sure noticed the stronger spring change from orange to pink. Brutal.
Heres a pic of Carter spring, and Eddy pink spring.
Totally unscientific, but factory Carter springs are probably on the stiffer side (depending on the engine). I don't know for sure, but I'd guess they were closer to the 8" springs in the Eddy kit. I'm sure, however, that every engine had a specific spring. I don't think you'll feel a difference between a 7" and an 8" spring. You have to be pretty far into the pedal to get into the power circuit most of the time. Have you checked cruise vacuum on your combination? Even if you're idling at 14", your cruise vacuum may be higher than that.

20230824_055102.jpg
 
Yeah, if the slightly stiffer springs made that much of a difference, I'd be swapping carbs just to see if something else was wrong. The Carter spring is almost sure to be stiffer than the pink spring.
 
Putting a known good carburetor on might help diagnose your problem.
 
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