4 plugs rich 4 perfect

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steelcutter

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I'm running a air gap duel plane intake with a 750cfm carb on my .03 over 318 with 360 heads, cam and tube headers. the problem; the cylinders on the runners from the shallow side of the intake are very rich. the ones deep side are perfect.
 
Seems a little odd to me. You could stagger it - but I'd be looking for a sealing issue either on the carb or the intake's head flange. Did it bolt on easy? The carb's a little big - and the heads are a little big - so it's more inclined to have reversion and puddling issues depending on the camshaft.
 
You didn't say if it was a 750 Edelbrock style or Holley vac secondary or double pumper. The eddy 750 tend to be rich right out of the box. And it sounds like fuel puddling.
 
well I started with a 650 Edelbrock and the thing ran very lean on all 8 (snow white). so I got the 750 I kind of new that it would be a little big but it was cheep. the funny thing is. It is only rich ( black smutty rich) on the 4 cyls. on the shallow side of the intake the other 4 are golden brown whats up with that
 
I think most dual planes feed the center two on one bank and the out board two on the other. You said the 750 was cheap. Was it used, new, or rebuilt? It could have been someone else's problem carb. As mentioned, improper sealing, float level, and unbalanced jetting can all cause this problem. The jets may be all the same but the metering rods or springs may not be a match. tmm
 
toolmanmike said:
I think most dual planes feed the center two on one bank and the out board two on the other. You said the 750 was cheap. Was it used, new, or rebuilt? It could have been someone else's problem carb. As mentioned, improper sealing, float level, and unbalanced jetting can all cause this problem. The jets may be all the same but the metering rods or springs may not be a match. tmm
Click to expand...

I was thinking the same thing. The 750 you have may have been messed with and is far from the way it was originally. To know weather a stock 750 would act on your set up you need to try one that you know is stock.
 
It is certainly a carb issue, because you changed the condition of the plugs with a carb swap, although CFM has little to do with it. that 650 was plenty, a carter TQ at 830 would also do what it needs to.

The engine is only going to use as much CFM as it needs at everything up to WOT. If it can use more, yeah, give it more, but CFM does not = fuel. It = fuel + air.

Pull the carb apart and look at what's in it. I'm wondering if you don't have a sticking metering rod piston.
 
Thanks for all the good input, The carb was use but I know the person I got it from The carb.is about a year old. ran good on his motor. He just wanted a holly. Guess he just wanted something to work on. HA!HA! Stock right out of the box. I have been through the carb it is all stock. What if I just change the springs on the metering rod to lighter ones. so the rods would stay down in the jet longer. 68 Dart GT
 
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